Debris Removal Programs

https://www2.peterson.af.mil/nssi

Boeing Gas Solution
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White Papers

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Space Team Project Final Technical Report 

Removing Orbital Debris: 

A Global Space Challenge  

Technical Report Authored By: 

 Lucy Rogers and Franz Gayl 

Space Team Member Roster: 

 Lucy Rogers, Eric Chiang, Yasemin Baydaroglu, and Franz Gayl 

Team Project Advisors:  

Yvonne Cagle, Marco Chacin, and Mona Hammoudeh 

Singularity University 

 Graduate Studies Program 2011 

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Table of Contents 

Executive Summary 

Chapter 1:  Introduction, Purpose, and Background 

Chapter 2:  Space Debris: An Exponentially Growing Threat 

Chapter 3:  The Proposed Sustainable Organization 

Bibliography 

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Executive Summary 

Satellites are in danger from catastrophic impact by space debris. This means that 

infrastructure critical to modern society is under threat – from power and water supplies, to 

military security and global navigation, from the conduct of global communications to 

commerce. This could affect billions of people. 

The rate of increase in debris is exponential, and left unaddressed, will lead to a runaway 

debris proliferation phenomena known as the “Kessler Syndrome.”  The resulting density of 

debris will threaten all space activities. 

Improved tracking and prediction of the path of debris can be enhanced through shared, 

accurate, and real time global space situational awareness. However, national security and 

military concerns of major space faring powers currently limits this ability. 

Mature NASA and industry orbital debris removal concepts, such as tethers and lasers 

remain underfunded and mainly untested. 

The aim of the Project is to develop a sustainable capability to develop and test 

technology, and to ultimately remove all dangerous debris from Earth orbital space by using 

mitigation, collision avoidance and debris removal techniques. 

We are looking to found an international organization dedicated to addressing threats to 

spacecraft, satellites and to the Earth, such as from space debris and asteroids. We will do this by 

influencing governments, businesses, and the public to seek and achieve better space situational 

awareness.  We will also work with those space stakeholders to improve mitigation and removal 

capabilities to improve the space environment upon which we have all come to depend. We will 

use practical experience, new technologies, knowledge and credibility to create long-term 

solutions for the Earth’s space environment and keeping corridors to Earth orbital space open. 

The potential stakeholders include space systems insurers and operators, but may also 

include cash rich countries that value involvement with cutting edge technologies and have the 

desire to help solve environmental issues, and also other countries who may wish to become 

space farers.  

We are uniquely placed to form this organization, as we are completely objective, with no 

national or industrial agenda. We are an international team, with experience in the private and 

public space industries, the military, and larger research communities. 

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Chapter 1: 

Introduction, Purpose, and Background 

1.  Introduction 

The Singularity University Graduate Studies Program of 2011 (SU GSP-11) Space Team 

selected a topic that met the following SU criteria: 1) the team project must employ exponential 

technologies and be dependent on them for success; 2) the product resulting from the team effort 

must benefit a billion people over a time span of ten years; 3) the selected topic must fit within 

the category of one of the SU’s six Grand Challenge problem areas, namely space, poverty, 

energy, global health, security or energy; 4) the team product must exhibit scalable and 

sustainable economics commensurate with the exponentially growing challenge it addresses; and 

5) the topic must present a compelling business case founded on a competitive concept of 

operations. Following discussion the Space Team proposed a research-founded product focused 

on solving the dilemma of Earth orbital space debris.  The project was found to meet the 

requisite criteria and approved by the SU faculty and staff. 

The team evolved into two subsections.  One section was focused on the physical quantification 

of, and technological solutions to the growing problem of orbital space debris.  The other section 

was focused on policy-related issues that impact space generally, and space debris specifically.  

The findings of the non-technical and policy-related Space Team section composed of Eric 

Chiang and Yasemin Baydaroglu was published in a separate document.  What follows in this 

document is a report of the technical research findings and conclusions of Lucy Rogers and 

Franz Gayl who formed the technical section of the Space Team. 

2.  Purpose 

The purpose of this paper is to define the specific ideas that the GSP-11 Space Team has 

developed in support of the debris related Space Team Project (TP).  The title of the GSP-11 TP 

research proposal is “Orbital Debris: A Global Space Challenge.”  The objective of the Space 

Team coming out of GSP-11 is to launch a sustainable organization dedicated to making orbital 

space safe for all of humankind.  This technology-intensive effort begins with a specific focus on 

mitigating and solving the growing threat from orbital debris.  

3.  Background  

In his article titled Overview of the legal and policy challenges of orbital debris removal [tt] 

published in the February 2011 edition of Space Policy, author Brian Weeden states: 

Since the launch of the first satellite in 1957 humans have been placing an increasing 

number of objects in orbit around the Earth.  This trend has accelerated in recent years 

thanks to the increase in number of states which have the capability to launch satellites 

and the recognition of the many socioeconomic and national security benefits that can be 

derived from space. There are currently close to 1000 active satellites on orbit, operated 

by dozens of state and international organizations. More importantly, each satellite that is 

placed into orbit is accompanied by one or more pieces of non-functional objects, known 

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as space debris. More than 20,000 pieces of space debris larger than 10 cm are regularly 

tracked in Earth orbit, and scientific research shows that there are roughly 500,000 

additional pieces between 1 and 10 cm in size that are not regularly tracked.  Although 

the average amount of space debris per cubic kilometer is small, it is concentrated in the 

regions of Earth orbit that are most heavily utilized...and thus poses a significant hazard 

to operational spacecraft. 

  

The sobering statistics documented by Weeden and many others prompted the GSP-11 Space 

Team to take a closer look at the orbital space debris threat.  Sharing an enthusiasm and 

professional backgrounds related to space, the team members united around a sense of mission to 

solve the problem rather than a business case.  The urgency of taking action to preserve the 

freedom to operate in and transport through Earth orbital space was clear to all members. 

Even in the absence of debris, humankind’s dependence on the Earth orbital space extends to 

military security of nations, position, navigation, and timing (PNT), and the conduct of global 

communications and commerce.  Satellite-enabled capabilities expose their vulnerability, as they 

constitute critical infrastructure for modern societies.  Humankind’s dependency leads to a 

bottleneck as nations compete for limited orbital real estate.  If unanticipated problems, man- 

made or natural, threaten key satellite constellation enabled capabilities such as PNT, serious 

civil and social disruptions can be predicted.  Preserving the conditions that permit space 

dependency represents a benefit that extends to all humankind.  Unfortunately, we continue to 

pollute the orbital space environment and threaten to initiate a devastating uncontrolled runaway 

proliferation of debris creation. Author Brian Weeden continues [tt]:  

In the late 1970s, two influential NASA scientists, Burt Cour-Palais and Donald Kessler, 

laid the scientific groundwork for what became to be known as the “Kessler Syndrome.” 

They predicted that at some point in the future the population of artificial space debris 

would hit a critical point where it grew at a rate faster than the rate at which debris is 

removed from orbit through natural decay into the Earth’s atmosphere. According to their 

models, large pieces of space debris would get hit by smaller pieces of debris, creating 

hundreds or thousands of new pieces of small debris which could then collide with other 

large pieces. This “collisional cascading” process would increase the population of space 

debris at an exponential rate and significantly increase the risks and costs of operating in 

space.   

Efforts at mitigation through better launch vehicle and satellite design and operations have 

proven successful.  But accidents still happen and debris growth outpaces natural reentry.  Also, 

efforts at better characterizing the environment through shared, accurate, and real time global 

space situational awareness (SSA) are stymied by national security concerns of major military 

powers.  Finally, mature orbital debris removal (ODR) concepts remain dormant.  Security 

parochialism and resource scarcity invite a catastrophe that will force the world into action.   

With this confirmation of Space Team concern in the background the GSP-11 Space Team 

researched: 1) if nations aspiring to go to space in the future should be invited to join space 

faring nations earlier in resolving orbital debris; 2) can more accurate SSA data be obtained from 

the U.S., Russia, and France for better global collision avoidance; and 3) what ODR technologies 

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are most hopeful in the near term to prevent the Kessler Syndrome.  The best vehicle for sharing 

team conclusions and recommendations was determined to be the inclusion of this report as an 

additional chapter in the Space Transportation Technology Roadmap, since New Space and 

space tourism would greatly benefit from orbital debris reduction and elimination. 

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Chapter 2: 

Space Debris: An Exponentially Growing Threat 

Chapter 3 is organized into three sections.  In the first the Space Team defines the problem of the 

exponential growth in space debris, to portray it as an urgent global need that calls for immediate 

solution.  The second section presents the state of the art in orbital debris mitigation, space 

situational awareness / collision avoidance, and debris removal concepts, followed by 

discussions of the gaps that remain as conclusions.  The third section restates the Space Team 

conclusions concisely in preparation for the final report chapter titled “Recommendations.”     

2.1  Defining the Problem:  Space Debris is an Exponentially Growing Threat 

Orbital space debris is any man-made object in Earth orbit which no longer serves a useful 

purpose.  Examples are derelict spacecraft, launch vehicle upper stages, payload fairings, debris 

from launch vehicle separation, debris from explosions or collisions, solid rocket motor 

effluents, paint flecks from thermal stress or particle impacts, and coolant droplets. 

            Figure 1.  Popular Science infographic depiction of satellite and debris populations. 

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In a 2010 report by the RAND National Defense Research Institute titled Confronting Space 

Debris - Strategies and Warnings from Comparable Examples Including Deepwater Horizon 

RAND observed [hh]:  

Moving to remediation...may require a “catastrophic” event that lowers the community’s 

risk tolerance, as has happened in other fields—which suggests the problem of orbital 

space debris may get worse before it gets better. 

The damage caused by debris to operational space systems can be catastrophic. The impacts of 

small particles cause erosive damage to operational satellites, similar to sandblasting.  This 

damage can be partly mitigated through the use of a protective "meteor bumper" which is widely 

used on spacecraft such as the International Space Station (ISS). However, not all parts of a 

spacecraft may be protected in this manner.  Solar panels and the optical components of 

telescopes, star trackers, and even portals and windshields are subject to constant wear by debris, 

and to a lesser extent, micrometeorites.  However, even a 1 cm object can prove catastrophic for 

a satellite: 

  Figures 2-3.  NASA test target (L), and debris after 7 km/sec impact with 1 cm Al object (R). 

A smaller number of the debris objects are larger, measuring over ten centimeters (3.9 in), and 

are far deadlier.   Against larger debris, the only protection is provided by maneuvering the 

spacecraft out of the way in order to avoid a collision.  Shielding against such hypervelocity 

debris is ineffective.  For example, a one kilogram object impacting at 10 kilometers per second, 

for example, is probably capable of catastrophically breaking up a 1,000-kg spacecraft if it 

strikes a high-density element in the spacecraft.  In such a breakup, numerous fragments larger 

than 1 kg would be created. 

If such a collision with larger debris occurs, many of the resulting fragments from the damaged 

spacecraft will themselves be in the one kilogram (2.2 lb) mass range or larger.  These then 

become an additional source of additional collision risk.  As the chance of collision is a function 

of the number of objects in space, proliferation leads to a critical density where the creation of 

new debris occurs faster than the various natural forces that remove these objects from orbit.  

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Beyond this threshold a runaway chain reaction can occur that reduces all objects in orbit to 

debris in a period of years or months.  

Currently, over 18,000 objects larger than 10 cm are known to exist. The estimated population of 

particles between 1 and 10 cm in diameter is approximately 500,000 [tt].  The number of 

particles smaller than 1 cm probably exceeds tens of millions.  In order to determine the number 

of orbital debris, large orbital debris (>10 cm) are tracked routinely by the U.S. Air Force Space 

Surveillance Network (SSN), the Russian Space Surveillance System (SSS), and the French 

Grande Réseau Adapté à la Veille Spatial (GRAVES).  In fact, objects as small as 3 mm can be 

detected by ground-based radars today, providing a basis for a statistical estimate of their 

numbers. Assessments of the population of orbital debris smaller than 1 mm can be made by 

examining impact features on the surfaces of returned spacecraft, although to date this has been 

limited to spacecraft operating in altitudes below 600 km.  

The principal sources of large orbital debris are satellite explosions and collisions. Prior to 2007, 

the principal source of debris was old upper launch vehicle stages left in orbit containing residual 

stored energy sources in the form of propellants and high pressure fluids.  Recently however, the 

major source of large debris has shifted to intentional and unintentional catastrophic events.  In 

January 2007 China employed a land-based missile to destroy the 2,200-pound Fengyun-1C 

weather satellite while it was orbiting 528 miles above the Earth. The impact left more than 

100,000 new pieces of debris orbiting the planet, NASA estimated, with 2,600 of them more than 

7 centimeters across.   Similarly, in 2008 the U.S. Navy shot down an inoperable spy satellite. 

The U.S. Navy AEGIS warship fired a single modified tactical missile, hitting the satellite 

approximately 247 kilometers over the Pacific Ocean as it traveled in space at more than 17,000 

mph.  Finally, an accidental collision between an American Iridium satellite and a Russian 

Cosmos satellite in 2009 greatly increased the number of large debris in orbit.  

The relatively small sum of  rocket bodies (approximately 2,000), non-operational spacecraft 

(approximately 3,000), and other debris measuring over 10 centimeters across (approximately 

5,000)  is eclipsed by the estimated tens of millions of pieces of space debris that are composed 

of small particles, less than one centimeter in any dimension.  For example, smaller pieces 

include dust from solid rocket motors, surface degradation products such as paint flakes, and 

coolant released by the notoriously polluting past Soviet Radar Ocean Reconnaissance Satellite 

(RORSAT) nuclear powered satellites. 

   

Figures 4-6.  Artistic depictions of RORSAT (L & C), and coolant debris discharge (R). 

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RORSATs were launched between 1967 and 1988 to monitor North Atlantic Treaty Organization 

(NATO) and merchant vessels using active radar.  Because a return signal from a target 

illuminated by a radar transmitter diminishes as the inverse of the fourth power of the distance, 

to operate effectively, RORSATs had to be placed in lower LEO.  RORSAT also required higher 

power radar and aerodynamic profile to compensate for those losses.  Large solar panels were 

ruled out in design because the low altitude orbit would have rapidly decayed due to drag 

through the upper atmosphere. Further, the satellite would have been useless in the shadow of 

earth. As a consequence, the majority of RORSATs were powered by nuclear reactors fuelled 

by uranium-235. At the end of their useful lives most of the nuclear reactor cores were ejected 

into a higher “disposal orbit."  Unfortunately, there were several failure incidents, some of which 

resulted in radioactive material re-entering the Earth's atmosphere. Although most nuclear cores 

were successfully ejected into high orbits, they will only decay after several hundred years.   

RORSATs were a major source of space debris in LEO.  During 16 reactor core ejections, 

approximately 128 kg of Sodium- Potassium Alloy (NaK-78) escaped from the primary coolant 

systems of the reactors. The smaller droplets have already decayed, but larger droplets of up to 

5.5 cm in diameter are still in orbit. The droplets will burn up completely in the upper 

atmosphere on re-entry but in the interim the major risk is impact with operational satellites.  The 

problems posed by RORSAT debris are diminishing with time as they reenter.  However, this 

single example of natural mitigation over time pales with many other flawed designs, outright 

failures, and careless operations that have caused the rate of debris growth to approach an 

exponential today, as graphically displayed below: 

Figure 7.  Tracked orbital debris population catalogued by U.S. Air Force as of 2010. 

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As for reentering debris, on average, reentering spacecraft break up at altitudes between 84-72 

km due to aerodynamic forces that cause the allowable structural loads to be exceeded.  Large, 

sturdy, and/or densely constructed satellites generally break up at lower altitudes. Solar arrays 

frequently break off the spacecraft parent body around 90-95 km because of the aerodynamic 

forces causing the allowable bending moment to be exceeded at the array/spacecraft attach point.  

Once the spacecraft body disintegrates, individual components that were housed in that parent 

body will continue earthward as fragments and receive aero-heating until they either demise or 

survive to impact the surface.  Spacecraft components that are made of low melting-point 

materials such as aluminum will usually evaporate at higher altitudes than objects that are made 

of dense materials with higher melting points such as titanium, stainless steel, and beryllium.   

      

      Figures 8-11. Various debris seen from within spacecraft, aircraft, and from the ground. 

If an object is enclosed in a substructure, the housing must first disintegrate before the internal 

component is exposed to destructive heating. Many objects have such a high melt temperature 

that they are able to survive reentry intact, although some of those are so light that they impact 

the surface with a very low velocity. NASA has noted that as a result, the kinetic energy of such 

light dense objects at impact is often under 15 Joules, a threshold below which the probability of 

causing a human casualty is negligible. During the past 40 years an average of one catalogued 

piece of debris fell back to Earth each day without causing serious injury or property damage. On 

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average, of those satellites that do reenter, approximately 10-40% of the mass of the object is 

likely to reach the surface of the Earth.   

Due to the Earth's surface being primarily water, most objects that survive reentry land in one of 

the world's oceans. In fact, the chances that a given person will get hit and injured during his/her 

one lifetime is estimated to be one in a trillion.  Prominent cases of uncontrolled reentry include: 

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n 1978, Cosmos 954 reentered uncontrolled and crashed near Great Slave Lake in the Northwest 

Territories of Canada. Cosmos 954 was nuclear powered and left radioactive debris near its 

impact site. In 1979, Skylab reentered uncontrolled, spreading debris across the Australian 

Outback, damaging several buildings and killing a cow.  The re-entry was a major media event 

largely due to the Cosmos 954 incident, but not viewed as much as a potential disaster since it 

did not carry nuclear fuel.   NASA had originally hoped to use a Space Shuttle mission to either 

extend Skylab’s life or enable a controlled reentry, but delays in the program combined with 

unexpectedly high solar activity made this impossible.  

Figures 12-15.  Orbital debris that have survived reentry and reached the Earth’s surface. 

Debris distribution is not uniform in Earth orbit.  Most orbital debris orbit within 2,000 km of the 

Earth's surface, as this realm has hosted the preponderance of orbiting satellites since the dawn 

of the space age.  Likewise, within this spherical shell volume the amount of debris varies 

significantly with altitude.  The greatest concentrations of debris are found near 800-850 km. In 

LEO (below 2,000 km), orbital debris circle the Earth at speeds of 7 km to 8 km per second.  

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However, the average impact speed of orbital debris in LEO with another space object will be 

approximately 10 km per second as there will be an angle of convergence in a collision. 

Consequently, collisions with even a small piece of debris will involve considerable energy.  

    

Figure 16.  Disproportionate object distribution across a random 180 degree panorama of LEO. 

While the U.S. Space Shuttle was still operational, when it was in orbit U.S. Air Force Space 

Surveillance Network (SSN) personnel regularly examined the trajectories of orbital debris to 

identify possible close encounters.  The same warning service is provided to the International 

Space Station (ISS).  If another object was projected to come within a few kilometers of the 

Space Shuttle, the spacecraft normally maneuvered away from the object if the chance of a 

collision exceeded 1 in 10,000.  The ISS has been required to do the same.   

Past on-orbit photographs of the now-deorbited Mir Space Station's exterior revealed evidence of 

large numbers of impacts from small orbital debris and meteoroids.  The most significant 

damage was evidenced on the large, fragile solar arrays which could not be protected from small 

particles.  To date orbital debris have caused no loss of mission or capability on the ISS.  This is 

in no small part due to the fact that the ISS is the most heavily shielded spacecraft ever flown.  

Critical components, such as habitable compartments and high pressure tanks, are designed to 

withstand the impact of debris as large as 1 cm in diameter.  Like the Space Shuttle, the ISS also 

has the capability of maneuvering to avoid tracked objects. The risk of a critical ISS component 

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being struck by debris 1 to 10 cm in diameter is slight and ways to reduce this risk are being 

investigated.  Still, a rise in the rate of ISS maneuvers to avoid collisions is notable.   

Exceptionally low altitude LEO systems such as Iridium, Orbcomm, and Globalstar do not 

encounter debris problems.  This is because debris at low LEO altitudes, whether caused by 

others or themselves, tends to slow due to atmospheric drag and deorbit relatively quickly.  

Often, upper stages and spacecraft are purposely placed in lower LEO after their missions have 

been completed in order to insure that higher drag forces will accelerate their fall back to Earth.   

As a general rule, the higher the altitude, the longer the orbital debris will remain in Earth orbit.  

Debris left in orbits below 600 km normally fall back to Earth within several years. At altitudes 

of 800 km, the time for orbital decay is often measured in decades.  Above 1,000 km, orbital 

debris will normally continue circling the Earth for a century or more.   

As for geostationary orbit (GEO), our ability to detect orbital debris at near 36,000 km altitude 

where many telecommunications and meteorological spacecraft operate is still somewhat limited.  

However, studies indicate that the orbital debris population is probably less severe there than in 

the aforementioned LEO altitudes.  Since GEO is a special natural resource having limited real 

estate and available “slots,” many spacecraft operators boost their old spacecraft into higher, 

disposal orbits at the end of their mission.  That orbit is said to be supersynchronous, and located 

at an altitude approximately 300 km higher than GEO.  Even without a debris problem at GEO, 

the limited and therefore crowded real estate that so many satellites share in GEO can still lead to 

collisions during maneuvers and the natural figure eight paths of satellites as they maintain 

position.  Such collisions can lead to loss of capability and new debris.    

Because they share an identical orbital inclination, eccentricity, and altitude in order to remain 

stationary with respect to terrestrial Earth, operational GEO spacecraft are rarely struck by 

anything but very small debris and micrometeoroids, with little to no mission effect.  Adding 

debris shields can further protect spacecraft components from particles as large as 1 cm in 

diameter.  The probability of two large objects >10 cm in diameter accidentally colliding in GEO 

is low.   

LEO is a more hazardous regime, and collisions do occur.  The worst such incident occurred on 

10 February 2009 when an operational U.S. Iridium satellite and a derelict Russian Cosmos 

satellite collided in which thousands of new debris were created, thousands large enough for 

SSN detection.  Viewed linearly, intuition dictates that in order to control the debris problem it is 

merely necessary to stop the production of new debris.  U.S. national policy recognizes this as a 

requirement since 1988, and the most recent National Space Policy (31 August 2006) includes 

the following statements concerning orbital debris:   

Orbital debris poses a risk to continued reliable use of space-based services and 

operations and to the safety of persons and property in space and on Earth. The United 

States shall seek to minimize the creation of orbital debris by government and non- 

government operations in space in order to preserve the space environment for future 

generations. 

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2.2 Kessler Syndrome 

Unfortunately, there is a non-linear component to debris growth that calls for urgent international 

action.  In spite of significant improvements in spacecraft design and  operations, there is a near 

term threat that existing debris densities may lead automatically to an uncontrolled chain of 

further collisions causing an exponential growth in debris density, even in the absence of further 

contributions.  This possibility is defined as the Kessler Syndrome. 

In 1978 NASA scientist Donald J. Kessler proposed a scenario in which the density of objects 

in LEO becomes high enough that collisions between objects could cause a cascade, with each 

ensuing collision generating new debris, thereby increasing the likelihood of further collisions.   

The theoretical scenario came to be called the Kessler Syndrome or Kessler Effect, brought on 

by collisional cascading or an ablation cascade.  One implication was and is that the distribution 

of debris in orbit could render space exploration, and even the use of satellites, unfeasible for 

many generations.   

Kessler held that every satellite, space probe, and manned mission has the potential to create 

space debris.  As the number of satellites in orbit grows and old satellites become obsolete, the 

risk of a cascading Kessler syndrome becomes greater.  Fortunately, at the most commonly-used 

orbits in low LEO, residual air drag helps keep the orbital zones free of debris.  Collisions that 

occur below this altitude are even less of an issue, since the energy lost in the collision results in 

fragment orbits having perigee below this altitude. 

At higher altitudes where atmospheric drag is insignificant, the time required for orbital 

decay and reentry is much longer.  Slight atmospheric drag, lunar perturbation, and solar 

wind drag can bring debris down to lower altitudes over time where fragments finally re-enter, 

but at very high altitudes this degradation can take millennia. 

The Kessler Syndrome is especially insidious because of the "domino effect" and associated  

"feedback runaway."  Any impact between two objects of sizable mass spalls off shrapnel debris 

from the force of the collision. Each piece of shrapnel now has the potential to cause further 

damage, creating even more space debris. With a large enough collision or explosion such as one 

between an active operational satellite and a defunct satellite, or the result of hostile actions in 

space, the amount of cascading debris could be enough to render LEO effectively impassable. 

There is growing consensus that this critical density has already been reached in certain orbital 

bands, especially polar LEO orbits where orbiting objects of high inclination converge at the 

poles dramatically increasing object density.  A runaway Kessler Syndrome would render the 

useful polar-orbiting bands difficult to use, and greatly increase the cost of space launches and 

missions.   

Richard Crowther of Britain's Defense Evaluation and Research Agency stated that he believes 

the cascade predicted by Kessler will begin around 2015.  The National Academy of Sciences, 

summarizing the view among professionals, noted that there was widespread agreement that two 

bands of LEO space, those at altitudes of 900 to 1,000 km (620 mi) and 1,500 km (930 mi), are 

already past the critical density. 

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      Figure 17.  Kessler’s 1978 collision prediction curves superimposed with actual collisions. 

In the 2009 European Air and Space Conference, University of Southampton, UK researcher, 

Hugh Lewis predicted that the threat from space debris would rise 50 percent in the coming 

decade and quadruple in the next 50 years.  Currently more than 13,000 collision close calls are 

tracked weekly.   

Because of the power-law size distribution, debris in the 5-mm-to-1-cm regime are estimated to 

represent about 80% of all objects larger than 5 mm.  Therefore, if the objective of space faring 

nations is to reduce the most significant mission-ending threat for most operational spacecraft, 

efforts need to focus on the 5mm- to 1 cm debris, as well as more massive debris and objects 

having greater cross-sections. 

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Figures 18-19.  Depiction of Kessler Syndrome (L), and Iridium-Cosmos collision (R). 

2.3 Comets, Asteroids, and Meteorites 

Meteoroids are thought to originate from the asteroid belt.  Meteoroids can range in size from 

micrometers to about a meter in diameter, well within the dimensional and mass parameters of 

man-made space debris.  In terms of material constituency and velocity meteoroids and asteroids 

are similar, with the exception that asteroids are larger, sometimes much larger.  If a meteoroid 

passes through the Earth’s atmosphere it is heated by friction, light, and perhaps an above ground 

detonation. This object is called a meteor if it burns up above the surface of the Earth. However, 

if a solid object lands on the Earth, it is classified as a meteorite.  

Meteoroids, asteroids and comets are in orbits about the Sun and fly past the Earth at high 

velocities.  Individual meteoroids are generally too small to be tracked and designated, a problem 

for smaller pieces of space debris as well.  However, the arrival time of meteor streams, such as 

the Leonids in November, can be predicted, and in the past NASA did not launch the Space 

Shuttle or plan spacewalk during such meteor showers.  

NASA, the U.S. Department of Defense (DoD), and other foreign space faring nations have long 

acknowledged that near earth objects (NEO) such as asteroids and comets can pose localized, 

broad geographic, or even global existential threats.  It has also not escaped their attention that in 

recent years the number of discoveries of new objects in both the professional and amateur 

astronomy communities has increased dramatically.  The increase is enabled primarily through 

improvements in the quality and numbers of optical instruments and information technology (IT) 

tools available to the science community and amateurs.  The proliferation of discoveries of so- 

called “minor planets” indicate that a larger number of natural objects exist, and potentially 

threaten Earth’s orbital space, if not our planet itself. 

Currently, naturally existent comets, asteroids and meteoroids are not classified as space debris, 

since they are not man-made and are both omnipresent in the near Earth and outer space 

environments.  From a scientific standpoint the separate classification is justifiable.  However 

from a practical standpoint in the so-called “space age” the threat they pose to spacecraft and 

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terrestrial Earth is indistinguishable from the threats posed by man-made space debris.  For the 

intended purposes of the Space Team project meteoroids, asteroids, and man-made objects are all 

classified as “debris” that contribute to the increasing density of objects in earth orbital space.  In 

the final analysis any improved space situational awareness, avoidance techniques, and kinetic or 

electromagnetic techniques used to dispose of hazardous man-made objects be equally useful in 

dealing with natural objects.   

Figures 20-21. Asteroid (L) and meteoroid (R), both constitute spacecraft-threatening debris. 

Gaps and Proposing Solutions: Orbital Space Debris Mitigation, Avoidance, and Removal 

NASA has concluded that controlling growth of the orbital debris population must be a high 

priority for the U.S., all major space-faring nations, and all nations that share an interest in 

preserving the near-Earth space global commons for all humankind. Measures can take the form 

of better space situational awareness to enable collision avoidance in the presence of debris, 

mitigating the threat of creating new debris through careful spacecraft design and operational 

procedures, and the development and employment of kinetic and electromagnetic tools for 

orbital debris removal (ODR). 

The NASA Orbital Debris Program Office [http://www.orbitaldebris.jsc.nasa.gov/] is the lead 

U.S. center for orbital debris research, and is recognized world-wide for its initiative in 

addressing orbital debris issues by taking the international lead in debris characterization and 

mitigation.  This includes conducting measurements of the environment and in developing the 

technical consensus for adopting mitigation measures to protect users of the orbital environment.  

Concurrently, the NASA Ames Research Center space debris research activities are making 

significant contributions to the larger NASA effort.  These activities are being led and 

coordinated by Chris Henze, Will Marshall, James Mason, Jan Stupl, and Creon Levit. 

NASA has confirmed a general international consensus that Kessler’s predictions were correct, 

and the conclusion that action must be taken is not controversial.  In this light, it can be argued 

that there are three general areas that must be addressed in order to interrupt or prevent the 

Kessler Syndrome problem, namely: 1) space debris mitigation; 2), collision avoidance, and 3) 

19 

orbital debris removal (ODR).  Each technique is clearly complementary of the others, and all 

will need to play a part in preserving the safe traficability of the near-Earth space environment in 

some fashion.  Furthermore, it can be argued that these efforts should be a shared international 

responsibility for all nations who have an interest in preserving the continued viability of the 

orbital space global commons.  Each area will be discussed in turn in the sections that follow.   

2.4 Space Debris Mitigation 

NASA defines space debris mitigation as “measures [that] can take the form of curtailing or 

preventing the creation of new debris, designing satellites to withstand impacts by small debris, 

and implementing operational procedures such as using orbital regimes with less debris, adopting 

specific spacecraft attitudes, and even maneuvering to avoid collisions with debris.”  Leading 

from the front, NASA in 1995 was the first space agency in the world to issue a comprehensive 

set of orbital debris mitigation guidelines. Two years later, the U.S. Government developed a set 

of Orbital Debris Mitigation Standard Practices based on the NASA guidelines.  

In response to the global space environmental threat, in 1993 the Inter-Agency Space Debris 

Coordination Committee (IADC) inter-governmental agency was formed with the specific aim of 

coordinating international efforts to deal with Earth orbital debris.  The IADC is comprised of 10 

countries as well as ESA, IADC members today include: 1) Italy (ASI), 2) France (CNES), 3) 

China (CNSA), 4) Canada (CSA), 5) Germany (DLR), 6) the European Space Agency (ESA), 7) 

India (ISRO), 8) Japan (JAXA), 9) U.S. (NASA), 10) Ukraine (NSAU), 11) Russia 

(ROSCOSMOS), 12) and England (UK Space Agency).  Other countries in the IADC followed 

NASA’s lead and created their own orbital debris mitigation guidelines.  In 2002, after a multi- 

year effort, the entire IADC adopted a consensus set of guidelines designed to mitigate the 

growth of the orbital debris population.   

In February 2007, the Scientific and Technical Subcommittee (STSC) of the United Nations' 

Committee on the Peaceful Uses of Outer Space (COPUOS) completed a multi-year work plan 

with the adoption of a consensus set of space debris mitigation guidelines very similar to the 

IADC guidelines. The guidelines were accepted by the COPUOS in June 2007 and endorsed by 

the United Nations in January 2008.  

Manufacturers and operators of spacecraft and upper stages are generally aware of the hazards of 

orbital debris and the need to mitigate their growth.  Many global firms voluntarily adhere to 

measures designed to limit the growth of orbital debris.  The U.S. Government, NASA and the 

Department of Defense (DoD) have also issued requirements governing the design and operation 

of spacecraft and upper stages to mitigate the growth of the orbital debris population. The 

Federal Aviation Administration (FAA), the National Oceanic and Atmospheric Administration 

(NOAA), and the Federal Communications Commission (FCC) also consider orbital debris 

issues in the licensing process for spacecraft under their auspices.  While the U.S. was at the 

forefront of these self-disciplining initiatives space faring nations have incorporated the same 

standards voluntarily or as a function of the IDAC.  

20 

2.5 Spacecraft Kinetic Protection 

In acknowledgement that orbital debris will continue to pose a threat to the spacecraft 

functionality, kinetic protection is generally being built into new spacecraft.  Hypervelocity 

impact measurements at NASA and other facilities worldwide are employed to assess the risk 

presented by orbital debris to new spacecraft.  New materials providing better protection such as 

the “bumpers” can be integrated in designs with less weight penalty.  Modeling and simulation as 

well as hypervelocity impact testing data also help in the analysis and interpretation of impact 

features on returned spacecraft surfaces.  Clearly, physical protection can only be effective 

against very small debris.  Centimeter size fragments will devastate most spacecraft (see Figure 

3), and fragments greater than 1 centimeter will threaten the habitability of the most heavily 

protected spacecraft, namely the ISS.  So, in the near-term protection represents a risk-accepting 

band aid solution to the growing debris problem.   

2.6 Controlled End of Life Satellite Disposal Practices 

Part of NASA’s efforts focus specifically on reducing the number of large objects, such as non- 

operational spacecraft and spent rocket upper stages orbiting the Earth.  One method of post- 

mission disposal is to allow the reentry of these spacecraft, either from natural orbital decay 

(uncontrolled) or a deliberate controlled entry.  Orbital decay can be accelerated artificially in 

order to lower the perigee altitude of an eccentric orbit so that atmospheric drag will cause the 

spacecraft to enter the earth’s atmosphere sooner. However, left to natural decay friction the 

surviving debris impact footprint on Earth often cannot be guaranteed.  To minimize 

uncertainties, controlled entry is normally achieved by the burning of more propellant through a 

larger propulsion system to cause the spacecraft to reenter the atmosphere at a steeper flight path 

angle. The vehicle will then impact at a more precise latitude and longitude, and the debris 

footprint can be positioned over an uninhabited region, generally into the oceans or other bodies 

of water or onto sparsely populated regions like the Canadian Tundra, the Australian Outback, or 

Siberia in the Russian Federation.  

To minimize the chances of damage to other vehicles, designers of new vehicles or satellites are 

frequently required to demonstrate that they can be safely disposed of at the end of their lives by 

use of a controlled atmospheric reentry system or a boost into a graveyard orbit.  In recognition 

of the increasing number of objects in space, NASA has adopted guidelines and assessment 

procedures to minimize the number of non-operational spacecraft and spent rocket upper stages 

orbiting the Earth.  One method of post-mission disposal is reentry of these spacecraft and upper 

stage launch systems, either from orbital decay (uncontrolled entry) or with a controlled entry.  

In order to preserve reentry options, launch and payload developers include reentry capabilities 

in the designs and margins of new systems.  Today these self termination capabilities include 

sufficient fuel, larger propulsion, and system flexibility to insure that the means to fire engines 

remain to achieve a lower altitude perigee.  Once there repeated exposure to higher atmospheric 

drag will accelerate the process of spacecraft reentry.  Controlled entry normally occurs by 

driving the spacecraft to enter the atmosphere at a steeper flight path angle. The object will then 

enter at a more precise latitude and longitude, and the impact footprint will predictably occur in a 

21 

nearly uninhabited region or in the ocean.  

The so-called Spacecraft Cemetery is an area in the southern Pacific Ocean 3,900 km southeast 

of Wellington, New Zealand where spacecraft such as the now defunct Mir Space Station and 

waste-filled Progress cargo ships are and have been routinely deposited.  While it is not the only 

controlled reentry impact footprint, it has been chosen for its remoteness so as not to endanger or 

harm human life.   

Similarly, at an altitude approximately 300 km above GEO there exists a so-called GEO 

“graveyard orbit.”  Alternatively referred to as supersynchronous orbit, junk orbit, or disposal 

orbit, it is an orbit significantly above GEO where many spacecraft are intentionally placed at the 

end of their operational life.  Graveyard orbit placement is a measure performed in order to lower 

the probability of collisions with operational spacecraft which are tightly packed into GEO slots.  

Otherwise the likelihood of collisions, failures and generation of new debris would be high.  A 

graveyard orbit is used when the delta-v required to perform a terrestrial de-orbit maneuver is too 

high.  Specifically, de-orbiting a GEO satellite requires a delta-v of about 1,500 m/s while re- 

orbiting it to a graveyard orbit only requires about 11 m/s.  One significant advantage of placing 

defunct satellites in the GEO graveyard is that future salvage operations may be capable of 

recycling and reusing old materials already preexistent on orbit.  Considering the energy saved in 

not needing to escape the Earth’s gravity well, salvaged materials will have significant value.  

       Figures 22-23.  South Pacific Spacecraft Cemetery (L), and GEO Graveyard Orbit (R). 

These space systems developer best practices of planning for termination will benefit future end 

of life disposal.  In the meantime, with many older systems and subsystems such capabilities 

were not built in and those objects are subjected to uncontrolled decay rates and reentry 

trajectories.  Since the surviving debris impact footprint cannot be guaranteed to avoid inhabited 

landmasses there can be risks to life and property.  Fortunately, to date no instance of significant 

damage or injury has been reported from an uncontrolled reentry.  

22 

Space Debris Mitigation Conclusions 

Considering the definition of space debris mitigation, the impact of ongoing international efforts 

to curtail or prevent the creation of new debris will certainly bear fruits in the future.    However, 

new launch vehicles and satellites designed and operated to both minimize new debris creation 

and withstand impacts by small debris will not help avoid collisions with or remove preexisting 

debris.  While debris mitigation measures can assume to be resourced by space faring members 

of the IADC, removal cannot.  This raises the issue of the limited membership of the IADC.  

Non-member nations may not have had space faring ambitions when the IADC was first 

convened, and may not even have active space programs today.  Yet every nation shares a future 

interest and stake in the space global commons.  In this regard orbital and outer space are no 

different than international terrestrial airspace and waters.  In fact the orbital mechanics laws that 

define operation in the domain lead to a ubiquitous and geographically non-specific shared 

ownership of each and every region of the Earth orbital domain.  Like Antarctica and the open 

seas, all nations and peoples have rights and responsibilities in space even before they launch 

indigenous space programs. 

This presents an argument for opening up IADC membership to nations that aspire to found their 

own formal space programs now or in the near future.  At a minimum, potential aspirants might 

include Saudi Arabia, Brazil, Australia, South Africa, Argentina, Chile, Malaysia, and the United 

Arab Emirates (UAE).  Even before embarking on national space initiatives, space aspirants 

could assist with currently unfunded and urgent near term aspects of the debris problem. For 

example, a nation could resource the development and demonstration of enabling technologies in 

support of orbital debris removal (ODR) (presented later in this paper).  In addition to the global 

prestige of developing such advancements in support of solving a vexing international threat, 

such contributions could be exchanged for valuable space guarantees in the future.   

For example, a space aspirant who develops an effective ODR capability could take the initiative 

to clear particularly polluted LEO altitude regimes such as 800 km – 1,000 km or 1,400 km – 

1,600 km.  In exchange for cleaning those altitudes the contributing nation would be provided 

U.N. enforceable rights to use the cleaned orbit that are at least proportional to the ODR 

investment.  This approach would over the longer term prove economical for the aspirant while 

demonstrating a global commitment to interrupt the Kessler Syndrome in its infancy.  Again, the 

technological and international prestige gained for that space aspirant is immeasurable. 

  

2.7 Space Situational Awareness and Collision Avoidance 

Global orbital space situation awareness (SSA) is a critical prerequisite to fully understanding 

the advancing maturity of the Kessler Syndrome.  Real time global SSA is also a critical 

prerequisite for satellite and debris collision avoidance in all space systems operations.  It is 

intuitive that global SSA suggests a penetrating understanding of the three dimensional spherical 

shell of Earth orbital space from the 100 km threshold of space to beyond GEO.  However, SSA 

also requires a precise understanding for the sake of planning and prediction.  The ability to 

precisely characterize our orbital space shell currently remains limited to a few nations.  Those 

nations are effectively limited to the U.S., Russia, and France, and to a lesser extent the ESA.  

23 

The SSA data sets of nation states are neither synthesized nor available to the global community 

at a degree of precision at which they were collected.  

  Figure 24.  High resolution-accuracy data provided earlier leads to superior collision avoidance. 

Lacking SSA synthesis and precision is due to the fact that the most capable SSA systems are 

compartmented national security systems of the U.S., Russia, and France.  In the end, the 

development of a globally accessible SSA common operating picture so urgently needed for 

collision avoidance in a high density debris environment is stymied.  This lack of integration and 

cooperation is unfortunate and does not help the IADC to address the issues of space debris and 

exchange information on research activities to identify debris mitigation options.  Guidelines are 

under development, which will forbid the intentional explosion of satellites such as the Chinese 

ASAT test, and state that precautions must be taken against accidental events that may produce 

space debris.  IDAC guidelines will also suggest that decommissioned satellites must be de- 

orbited and destroyed in the atmosphere, if this is impossible.  This is usually the case for 

defunct satellites in GEO, and increasingly for newer systems in LEO and MEO.  Still, even the 

IADC cannot compel higher accuracy data to be provided by the U.S. or any other space 

surveillance capable nations for collision prediction and avoidance.   

24 

Figure 25.  Accurate data leads to superior collision avoidance decisions. 

The foundation of global SSA goes back to the birth of the space age, during which the first 

man-made space objects began to be numbered and catalogued.  Today there are nearly 20,000 

large objects in our Earth orbital system that are tracked, but only about 700 are operational 

satellites.  The rest constitute large, trackable debris at least 10 centimeters in one dimension of 

the sort discussed throughout this paper.  For all space users it is important to know the location 

of all working satellites so that information, commands and other data can be transferred 

between them and ground stations effectively.  By the same token it is important to know where 

the dead satellites and larger debris are so that collisions with working systems can be avoided.   

Since the beginning of the space age, there have only been a handful of collisions between 

tracked items (see Figure 17), however the rate of collisions is increasing with time, as Kessler 

predicted.   Even though the probability of a collision between two objects larger than about 10 

centimeter diameter remains low, manned systems such as the ISS are directed to execute 

avoidance maneuvers if there is a 1 in 10,000 possibility of hitting another object.  Just as 

25 

important as mitigating new debris creation and ultimately removing it from orbit, so too is 

awareness of the environment to avoid collisions given debris pollution.  Accurate numbering 

and cataloguing orbiting objects for accountability is critical in this regard.   

At the visibility level of the IADC, each man-made object that is known to be tracked in space is 

assigned a unique International Identification Number (IIN), also called the International 

Designator.  Today, the international designation now consists of three parts consisting of the 

year of the launch, the number of the launch in that year and a letter or letters for each object 

resulting from that launch. The payload is often assigned the letter A.  Any subsidiary scientific 

payloads in separate orbits will be labeled B, C, etc. and then inert components, for example, the 

burnt out rocket casing, are designated D, E, etc. The letters I and O are not used, to avoid 

confusion with numbers. If there are not sufficient letters to label every piece of debris resulting 

from a particular launch – such as from an explosion in orbit - then double letters are used 

starting with AA–AZ, followed by BA–BZ, and so on, until ZZ is reached.  For example, the 

Vanguard 1 which was launched in 1958 is the oldest artificial satellite still in orbit, and has the 

IIN 1958-002B, while the Hubble Space Telescope (HST) which was launched from a Space 

Shuttle in April 1990, has the IIN 1990-037B.   

A space catalogue is another comprehensive list of man-made objects in space. A catalogue list 

includes the type of object, its orbit, and where it originated so that even larger objects whose 

origin cannot be determined are accounted for and tracked.  Catalogues are clearly more useful 

for nations than IINs.  The IIN of an object is useful in building a catalogue, but just as an input.  

Recall that any object in the international catalogue will only benefit from the currency and 

accuracy that nations are willing to share.  Catalogues are real time comprehensive pictures of 

space objects defined to the resolution of the sensors owned by the organizations that populate 

the catalogues.  The space faring nations that consider space a national security and potential 

warfighting domain have their own compartmented catalogues.  The currency and accuracy of 

those catalogues will naturally remain privy to the owning nation’s defense network.  As noted 

earlier, what is provided to the IDAC catalogue is dumbed down and incomplete.  In order to 

understand existing capabilities the capabilities and limitations of the world’s most robust SSA 

systems are introduced below.  

2.7.1 U.S. Space Situational Awareness Capabilities 

The U.S. collects the most comprehensive and accurate measurements of near-Earth orbital 

space.  Debris characterization using ground-based radars and optical telescopes, space-based 

telescopes, and analysis of selected spacecraft surfaces that are returned from space intact 

contribute to U.S. SSA.  The set of sensors used for these measurements are primarily owned and 

operated by the Department of Defense (DoD).  The sensor system of systems is known as the 

U.S. Air Force Space Surveillance Network (SSN).  The SSN will be described later. Some 

platforms and systems are primarily dedicated to the debris characterization task.  They include 

specialized radars such as the Haystack, and examination of returned surfaces from the Solar 

Max, the Long Duration Exposure Facility (LDEF), the Hubble Space Telescope (HST), and the 

now-retired Space Shuttle fleet.  However, all of the systems that are owned and operated by the 

U.S. DoD have as their primary mission the production of real time SSA for U.S. national 

26 

security, severely restricting public data sharing.   

Accordingly, U.S. national security space sensors capture the global debris picture.  They permit 

collision prediction and space traffic management that is superior to any other network in 

existence.  Yet, the high levels of object resolution, position accuracy, and orbital parameters are 

not available to the public, commercial space entities, and much less the international 

community.  The data that is provided to users outside of the U.S. national security space 

community is deliberately “dumbed down” to an inferior resolution and accuracy so that the 

actual capabilities of U.S. systems are not compromised.  While this is understandable from the 

standpoint of protecting state secrets, it presents a vexing frustration for an international 

community collectively threatened by the runaway proliferation of orbital debris.  

2.7.1.1 U.S. Tracking and Monitoring of Launch Vehicles 

Ideally, the tracking, identifying, and cataloguing of space debris should be an end-to-end life- 

long object record that begins at the launch of a satellite into space and terminates with its 

reentry or graveyard orbit storage.  National security restrictions, deliberate events, and 

unexpected accidents prevent and/or complicate this ideal degree of international debris 

transparency.  Nevertheless, many less sensitive commercial and scientific missions have utilized 

cameras to track and monitor initial mission progress.  

The now-retired Space Shuttle serves as a good example of superior initial tracking and 

monitoring.  Following the return-to-flight of the Space Shuttle in July 2005, the number of short 

range tracking cameras based on the launch pad at the John F. Kennedy Space Centre in Florida 

was increased to six.  The images from those cameras were thoroughly examined after each 

subsequent launch to ensure no damage occurred to the Shuttle. There were also separate 

dedicated cameras for the top and bottom halves of the Shuttle and also for the hydrogen vent 

arm above the external tank, the underside of the Shuttle’s left and right wings and also the area 

between the external tank and the Shuttle. The short range cameras covered the launch from T-10 

through to T + 57 seconds, after which the Shuttle was too far away for good quality images to 

be produced. Seven medium range trackers were located outside of the launch pad and provided 

data points for the calculation of the flight paths and also multiple views of the Shuttle during 

launch, which were also examined later for possible damage. These cameras recorded everything 

from T – 7 through to T + 110 seconds. Long range trackers recorded between T − 7 and T + 165 

seconds and provided data points to track the Shuttle as it climbed into orbit.  While the Shuttle 

is retired, the best launch tracking practices continue to be followed in the U.S..   

Following orbital insertion the depleted launch components of the Shuttle were designed to fall 

back to Earth quickly.  Once in orbit the Shuttle commenced to be tracked by the world-wide 

NASA sensors and more significantly the distributed Space Surveillance Network (SSN) run by 

the U.S. Air Force.  This sensor hand-off is also done with all other U.S. satellites, and given 

cues from other sensors also with SSN observations of foreign satellite launches.  Conversely, 

foreign surveillance systems such as those of Russia and France likewise track and monitor not 

just their own launches but also those of others, such as the U.S.  Unfortunately, the 

27 

comprehensive data sets available to select nations are not made available to the international 

effort to track and monitor debris. 

The methods used to track all objects orbiting the Earth, both manmade and natural, include 

optical, radio, and radar techniques. For objects in LEO between about 200 and 2,000 kilometers 

above the Earth radar is a useful method.  At Medium Earth Orbit (MEO) and out to and 

including GEO at 35,880 kilometers altitude, optical telescope observations are able to detect 

much smaller objects than radars, and so are the preferred ground to space sensors.  For example, 

Global Positioning System (GPS) satellites fill a MEO constellation located at approximately 

20,000 km altitude. 

The sensors used by ground-based systems are categorized as either active or passive. Active 

sensors, such as radar, send out energy and read the returned signal. Satellites or spacecraft that 

include equipment that make them easily tracked by a specific method are called cooperative 

objects.  Dead satellites whose attitudes are no longer correct, and space debris are called non- 

cooperative objects.  Passive sensors are usually used to detect non-cooperative objects, although 

if their geometry is suitable (10 cm today, <10 cm in the future) to reflect a signal, an active 

radar sensor can still be used to track it so long as the object is in LEO.  Passive sensors include 

optical telescopes that detect the sunlight reflected from the satellite.   

Due to non-periodic perturbations, orbits of satellites and space debris must be recalculated and 

checked periodically.  These perturbations result from gravitational variations of the moving 3 

body Sun-Moon-Earth system and unpredictable changes in atmospheric drag due to 

spontaneous ultraviolet light (UV) and particle flux from solar storm activity, and the effects of 

high altitude winds on low altitude LEO orbits.  To keep track of all that humankind has put into 

space in real time, large portions of the sky must be observed in detail continuously. In fact, most 

objects are tracked on a regular basis by at least one of the many systems around the world, 

though single a high-granularity shared SSA picture for international use is still lacking. 

  

2.7.1.2 U.S. Air Force Space Surveillance Network and Space Catalogue 

The U.S. Department of Defense (DoD) has maintained a database of satellite states since the 

launch of Sputnik in 1957.  As part of their space surveillance mission for the U.S. Strategic 

Command (USSTRATCOM), the U.S. Air Force Space Command, located at the Space Control 

Centre inside Cheyenne Mountain Air Force Station in Colorado Springs, is responsible for 

tracking all objects orbiting the Earth that are larger than 10 centimeters in any dimension.  

Currently, the Air Force employs Very High Frequency (VHF) radar tracking systems in what is 

known as the “Air Force Space Fence.”  Higher resolution tracking is planned with Ultra High 

Frequency (UHF) and other, shorter wavelength radar systems in the future.  The Space Control 

Center then monitors and updates the a space catalogue.  A backup system, provided by the US 

Naval Space Command, is called the Alternate Space Control Center, and is designed to continue 

space surveillance if the Space Control Center were unable to function.  The resulting catalogue 

is still often referred to as the USSPACECOM Catalogue, or just the Space Catalogue.  Data for 

these objects is collected and updated continuously by the aforementioned Space Surveillance 

Network (SSN).  Two separate catalog databases are maintained under the U.S. Strategic 

28 

Command (USSTRATCOM): a primary catalog created and maintained by the Air Force Space 

Command (AFSPC), and an alternate catalog by the Naval Space Command (NSC). The number 

of cataloged objects is over 20,000.  Different astrodynamic theories are used by AFSPC to 

maintain these catalogs in order to achieve a time-averaged optimal synthesis of the different 

results.   

The SSN is also known as the “SPACETRACK” Program.   It consists of an integrated set of 

dedicated, collateral, and contributing electro-optical, and passive and active radio frequency 

(RF) sensors that are distributed worldwide.  The SSN is dedicated to detecting, tracking, 

cataloging and identifying artificial objects orbiting Earth.  These include active and 

inactive satellites, spent rocket bodies, and fragmentation debris. Space surveillance 

accomplishes the following: 1) predict when and where a decaying space object will re- 

enter the Earth's atmosphere; 2) prevent a returning space object, which to radar looks like a 

missile, from triggering a false alarm in missile-attack warning sensors of the U.S. and other 

countries; 3) chart the present position of space objects and plot their anticipated orbital paths; 4) 

detect new man-made objects in space;  5) produce a running catalog of man-made space 

objects; 6) determine which country owns a re-entering space object; and 7) 

inform NASA whether or not objects may interfere with satellites and ISS orbits.   

In developing, improving, and updating the Space Catalogue AFSPC employs the so-called 

General Perturbations (GP) theory for analytical solutions of the satellite equations of motion. 

The orbital elements and their associated partial derivatives are expressed as series expansions in 

terms of the initial conditions of these differential equations.  Today, assumptions must be made 

to simplify these analytical theories.  These include truncation of the Earth’s gravitational 

potential to a few zonal harmonic terms. Also, the atmosphere is usually modeled as a static, 

spherical density field that exponentially decays, not a faithful reflection of non-periodic 

anomalies such as those caused by extreme solar activity.  Third body influences and resonance 

effects are partially modeled.  Increased accuracy of GP theory will require significant 

development efforts.  NASA maintains civilian databases of GP orbital elements, also known as 

NASA or North American Aerospace Defense Command (NORAD) two-line elements (TLE).  

The GP element sets are "mean" element sets that have specific periodic features removed to 

enhance long-term prediction performance, and require special software to reconstruct the 

compressed trajectory. 

The current U.S. SSN has difficulty in cataloging some space objects in highly elliptical orbits 

(HEO) and low-inclination orbits.  Objects in HEO are difficult to detect because they spend a 

large fraction of their time at very high altitudes, while objects in low-inclination orbits are more 

difficult to detect because of the relative lack of U.S. ground-based sensors at or dedicated to low 

latitudes.  Also, while there are an estimated 600,000 objects larger than 1 cm (0.4 in) in orbit, 

the SSN only actively tracks space objects which are 10 centimeters in diameter (softball size) or 

larger.  The SSN does not monitor every object continually, but does spot checks to ensure that 

the objects are where they are expected to be. This is due to the limitations of the network in 

terms of geographic distribution, capability and availability.  Nevertheless, well over 100,000 

observations are made each day.  It should be emphasized that these limitations and peculiarities 

do not represent deficiencies in the way the SSN performs its mission of maintaining an object 

29 

catalog of relevance to U.S. national security.  It does however highlight the fact that the U.S. 

SSN, as the global state of the art in such networks, is not optimized to characterize the entire 

global space debris population in support of an international environmental threat.  What follows 

are short descriptions of the various sensors and sensor sets that make up the U.S. SSN: 

Figure 26.  The SSN includes passive and active radar and optical sources distributed worldwide. 

2.7.1.3 Optical Tracking of Satellites and Debris 

Optical tracking is currently used by the SSN for tracking both space debris and satellites.  It is 

also used during the launch of space vehicles.  In the U.S. optical tracking systems were first 

developed in 1956 and fielded in 1958.  This constituted a worldwide network of stations, whose 

aim was to obtain enough accurate photographs of satellites to be able to determine highly 

precise orbits. Special cameras, designed by James G. Baker and Joseph Nunn provided the 

tracking information.  The Baker Nunn system imaged satellites at an altitude ranging from 

about 4,800 kilometers to 35,800 kilometers.  The Baker Nunn system suffered from two major 

drawbacks.  First, as film was used as the detector, it had to be developed.  This limited how 

quickly the results were available. Second, in order to detect satellites personnel had to look for 

streaks across the photograph as the film had to be scanned manually. This was time-consuming 

and open to human error. As technology advanced, the Baker Nunn cameras have been replaced 

by a new system known as the Ground based Electro-Optical Deep Space Surveillance. 

2.7.1.3.1 Ground-based Electro-Optical Deep Space Surveillance (GEODSS) 

GEODSS tracks objects in deep space, or from about 3,000 mi (4,800 km) out to beyond 

GEO altitudes.  Each GEODSS site has three telescopes each facing a different section of the 

sky.  Each telescope has a 40-inch (1.02 m) aperture and two special mirrors that form focused 

30 

images over a 2° field of view.  In comparison, the full Moon is only about half a degree wide.  

The visible wavelength telescope detectors are able to detect objects 10,000 times dimmer than 

the human eye is capable of, down to a magnitude of about 16.  GEODSS sensors can image 

objects as small as a basketball located in a GEO.  GEODSS is a vital part of the SSN, as it can 

even detect Molniya satellites in HEO at apogee distances that even surpass the Moon (245,000 

miles). Each GEODSS site tracks approximately 3,000 objects per night out of 9,900 object that 

are regularly tracked and accounted for by the SSN.  

There are three fixed-permanent GEODSS sites controlled from the U.S. Edwards Air Force 

Base, California. They are located in Socorro, NM; Maui, HI; and Diego Garcia in the Indian 

Ocean.  A mobile telescope that contributes to the GEODSS system is located at Morón Air 

Base, Spain.  The GEODSS telescopes electro-optical sensors in that they employ low light level 

TV digital cameras and a computer instead of film for digital, transferable images.    Optics 

sensitivity and sky background during daytime that masks satellites reflected light, dictate that 

GEODSS sites operate at night.  As with any ground-based optical system, full moons, cloud 

cover, and local weather conditions directly influence its effectiveness.  The telescopes scan the 

sky at the same rate as the stars appear to move, thus keeping the stars in a fixed position in the 

field of view.  As the telescope is scanning, cameras take rapid snapshots.  Computers then 

overlay these images onto each other. As the stars have remained in the same position, they are 

easily electronically erased, leaving only items moving with respect to the star background. This 

includes man-made space objects, asteroids and comets, all of which appear as streaks across the 

image. From measurements of the streaks, the orbits of the objects in space can be calculated. 

The type of telescope is called a Ritchey–Chretien design and is also used for the Hubble Space 

Telescope’s optical system.   

      Figures 27-29. GEODSS sites at Diego Garcia (L), Maui, HI (C), and Socorro, NM (R). 

2.7.1.3.2 Space Based Surveillance System 

The Space-Based Visible (SBV) sensor, an electro-optical camera that works in the visible light 

band of the spectrum, provides useful data to the SSN.  The SBV sensor can detect faint objects 

near the sunlit limb of the Earth and also has the ability to scan large areas of the sky.  Onboard 

signal processing reduces the amount of data produced to a manageable size. SBV operates for 

eight hours per day and gathers as many observations as the GEODSS ground based sites, and is 

considerably more accurate than the GEODSS sensors.  To replace the SBV sensor, the first of a 

constellation of five satellites forming a Space Based Surveillance System (SBSS) is currently 

being built. SBSS will also be an integral component of the SSN.  The constellation will operate 

31 

in LEO but will look at objects up to a GEO using a visible-spectrum telescope. The SBSS aims 

to survey an area of interest a few times a day as opposed to every few days with the current 

SBV.  Another program that was intended to compliment the SBSS was the Orbital Deep Space 

Imager. It was to be a space telescope that would have produced high-resolution images of 

objects in GEO; however, due to budget restraints an operational system is not currently being 

developed. 

    Figures 30-32.  SBSS artist rendition (L), in production (C), and notional operational system. 

2.7.1.3.3 Air Force Maui Space Surveillance System 

The Maui Space Surveillance System (MSSS) provides a satellite tracking capability using a 

3.67-meter telescope known as the Advanced Electro-Optical System (AEOS).   The MSSS is 

also commonly referred to as the Air Force Maui Optical and Supercomputing (AMOS) 

observatory.  It is owned by the DoD, and is the U.S.’s largest optical telescope designed for 

tracking space objects, .  The MSSS is routinely involved in numerous observation programs in 

support of the SSN.  The MSSS also has the capability to project lasers into the atmosphere for 

the purpose of characterizing a specific path in real time in order to adjust the adaptive optics of 

the mirror aperture for optimization of imagery resolution.  The MSSS is situated at the crest of 

the dormant Haleakala volcano at an altitude of 3,058 meters.  It is noteworthy that in the process 

of accomplishing its primary mission to track and characterize man-made objects, the MSSS has 

discovered a number of asteroids.  Accordingly, through its primary mission for Air Force Space 

Command, the MSSS has combined large-aperture tracking optics with visible and infrared 

sensors to collect data on near Earth and deep-space objects.   

The 75-ton AEOS telescope points and tracks accurately, yet is fast enough to track LEO 

satellites, ballistic missiles, and selected debris.  As noted, AEOS is equipped with an adaptive 

optics system (AO), the heart of which is a 941-actuator deformable mirror that can change its 

shape to remove the atmosphere's distorting effects.  This permits scientists to get near 

diffraction-limited images of space objects, including debris, by removing  the effects of 

scintillation  from atmospheric turbulence.  Other equipment at the MSSS site includes a 1.6- 

meter telescope, two 1.2-meter telescopes on a common mount, a 0.8-meter beam 

director/tracker, and a 0.6-meter laser beam director.  

32 

   Figures 33-34. Maui Space Surveillance System (MSSS) seen from above and from the side. 

2.7.1.3.4 Starfire Optical Range 

The Starfire Optical Range (SOR) is located at the U.S. Air Force Research Laboratory (AFRL) 

on Kirtland Air Force Base in Albuquerque, NM.  The primary mission of SOR is to research, 

develop, and demonstrate optical wavefront control (i.e. AO) technologies that cancel the 

distortions from atmospheric turbulence that interferes with laser beam integrity over long 

distances.  The range is a secure lab facility, and is a division of the Directed Energy 

Directorate of AFRL.  According to the Air Force, SOR's optical equipment includes a 3.5 

meter telescope which along with MSSS is one of the U.S.’s largest telescopes.  Like the Maui 

MSSS, the SOR is equipped with adaptive optics designed for both its research mission and 

satellite tracking, in fact SOR research improves MSSS’ performance.  SOR also conducts 

research into the use of lasers as a means for long-distance, high-bandwidth, free space 

communications.  Fidelity of the optical carrier in air-to-air laser connectivity is important for 

data integrity.  SOR also studies the effects of scintillation as it pertains to the development high 

energy laser (HEL) weapons.  The SOR is also an integral component of the SSN. 

33 

Figures 35-36. Starfire Optical Range (SOR) seen from above (L) and from below (R). 

2.7.1.3.5 Space Surveillance Telescope 

The Space Surveillance Telescope (SST) program began as a Defense Advanced Research 

Projects Agency (DARPA) initiative to develop a ground based optical system for detection and 

tracking of faint objects in space such as asteroids and orbital debris.  It is also to be employed in 

support of space defense missions. The program is designed to advance, or expand, space 

situational awareness, and in this be able to quickly provide wide area search capability.  The 

large, curved focal surface array sensors of the SST are innovative designs that encompass 

improvements in detection sensitivity, allow for a shorter focal length, a wider field of view, and 

provide improvements in step-and-settle abilities.  SST detects, tracks, and can discern small, 

obscure objects, in deep space with a "wide field of view system."  It is a single telescope with 

dual abilities.  First the telescope is sensitive enough to allow for detection, of small, dimly lit, 

low reflectivity objects.  Second it is capable of quickly searching the visible sky.  This 

combination is a difficult achievement in a single telescope design.   

The SST is an F/1.0 aperture telescope with a 3.5 meter primary mirror like SOR’s that can 

capture more light in a day than a conventional telescope can capture in a week.  It is capable of 

delivering wide-angle views of the Earth's firmament thanks to a curved, focal plane array/CCD. 

Multiple searches can be conducted from the ground several times throughout the night. As a 

telescope system, it can give precise locations of discovered objects, extrapolate the course of the 

object, and indicate the objects stability, all crucial for SSN awareness.  The telescope's primary 

task will be to look for man-made space debris, microsatellites, meteors or other objects moving 

at the same speed at which the Earth rotates, namely at GEO.  The US Air Force has been 

transitioning the capability and integrated the SST as a sensor set within the SSN.  The system 

developed its first images in early 2011, and the Air Force may place SSTs all over the world, 

creating 360-degree surveillance coverage of GEO  in order to keep U.S. spacecraft aware of 

avoidable environmental hazards. 

34 

       Figures 37-38.  DARPA Space Surveillance Telescope (SST) as rendition and operational. 

2.7.1.4 Space Fence or US Air Force Fence 

The Air Force Space Surveillance System (AFSSS) is an array of multistatic radar antennas 

spread across the southern USA that is used as an interferometer to make precise measurements 

of the path of satellites and other objects as they pass over the USA.  It is the detection and 

tracking foundation of the NSS.  It is a VHF (30 - 300 MHz) Band capability to detect objects 

down to 10 cm in LEO.  An upgrade to the system is planned to replace the VHF transmitters 

with S-Band (2 - 4 GHz) radar systems capable of detecting 5 cm to a range of 160–1,000 in 

LEO.  The S-band system will also allow faster revisit times and, as the radars themselves will 

be distributed over a wider geographical area, it will also give a wider view of the sky, and 

capable of detecting objects as small as 10 cm at altitudes up to 30,000 km. Today, the AFSSS 

detects space objects originating from new launches, maneuvers of existing objects, breakups of 

existing objects, natural objects such as meteorites and asteroids, and provides data to users from 

its catalog of space objects. Orbital parameters of nearly 20,000 objects are currently maintained 

in the catalog developed by the AFSSS, a critical resource which now has gained usage by 

NASA, weather agencies, and even friendly foreign agencies. 

The current VHF-based AFSSS includes 3 known transmitter sites.  The master station is located 

at at Lake Kickapoo, Texas, and two other transmitters are located at Gila River, Arizona and 

Jordan Lake, Alabama.  There are 6 known receiving stations, namely: San Diego, CA, Elephant 

Butte, NM, Red River, AR, Silver Lake, MS, Hawkinsville, GA, and Tattnall, GA.  The 

receiving stations at Elephant Butte and Hawkinsville are considered to be "High Altitude" 

stations with longer and more complex antenna systems that are designed to see targets at higher 

altitudes than the other four receiving stations. 

The future upgraded AFSSS will have S-Band radar stations  spread out across the continental 

U.S. at roughly the level of the 33rd parallel north, running from California to Georgia.  As an S- 

Band capability with ground-based transmitters and multiple receivers it is designed to perform 

uncued detection, tracking and accurate measurement of smaller orbiting space objects.  

35 

Figures 39-40.  Legacy VHF fence transmitter (L), and future S-Band transmitter (R). 

2.7.1.4.1 Precision Acquisition Vehicle Entry Phased Array Warning System PAVE PAWS 

The United States Air Force Space Command Precision Acquisition Vehicle Entry Phased Array 

Warning System (PAVE PAWS) is a system of ground-based ultra high frequency (UHF) phased 

array radars that are located around the world.  PAVE PAWS constitutes the heart of the U.S. 

Ballistic Missile Early Warning System (BMEWS).  The UHF band of PAVE-PAWs covers the 

UHF radio frequency band from 300 megahertz to 3 gigahertz. Published site locations include 

but are not necessarily limited to: Flyingdales, England; Beale AFB, CA, Cape Cod, MA, 

Shemya Island, AK; Clear AFS, AK; Thule, Greenland; Cavalier AFB, ND; Eglin AFB, FL; 

Robins AFB, GA; and perhaps other sites.   

Traditionally, the primary mission of PAVE PAWS has been to detect and track sea-launched 

ballistic missiles (SLBM) and intercontinental ballistic missiles (ICBM) entering North 

American air space, with a secondary mission to track satellites.  Information received from the 

PAVE PAWS radar systems pertaining to SLBM, ICBM, and satellite detection is forwarded to 

the USSTRATCOM facilities at Cheyenne Mountain Air Station, Colorado.  Beyond its early 

warning mission and satellite tracking missions, PAVE PAWS now also serves as valuable 

collection sources for the real-time refinement of the growing catalogue of detectable debris. 

36 

  Figures 41-42.  A PAVE PAWS site (L), and phased planer array beam steering principles (R). 

2.7.1.4.2 Haystack Radar 

The Millstone/Haystack complex is owned and operated by Lincoln Laboratories of the 

Massachusetts Institute of Technology (MIT). Millstone/Haystack is part of the Lincoln Space 

Surveillance Complex (LSSC), which consists of four large-aperture high-power radars: 1) the 

Millstone Hill Radar (MHR) L-Band, 2) the MHR UHF, 3) Haystack Long-Range Imaging 

Radar (LRIR), and 4) the Haystack Auxiliary (HAX) Radar.  The LSSC sensors are contributing 

sensors to the SSN. MHR and Haystack LRIR are both located in Tyngsboro, Massachusetts.  

MHR is a deep-space radar that contributes 80 hours of space surveillance per week to the SSN. 

Haystack is a deep-space imaging X-Band radar that provides wideband SOI data to the SSN one 

week out of every six. 

Measurements of near-Earth orbital debris are accomplished by conducting ground-based and 

space-based observations of the orbital debris environment. As components of the SSN, 

the Haystack X-Band Radar radiates at 22-25 GHz, 35-50 GHz, and 85-115 GHz frequency 

bands to capture RF imagery of object details at 1-10 cm resolution. The Haystack Radar 

currently operates in the 9.5 GHz to 10.5 GHz frequency band, and is scheduled to be upgraded 

to a millimeter-wave (MMW) radar that operates in the 92 GHz to 100 GHz frequency band.  

The new radar will use innovative transmitter design and signal processing to achieve image 

resolution that is about 10 times better than what is currently available.  The existing 37 meter 

(120 foot) antenna will be replaced by a new dish, accurate to 0.1 millimeter (0.004 inch) over its 

entire surface, which is a factor of 3 better than at present.  The new antenna will also permit the 

Haystack radio-telescope to operate in the 150 GHz range or higher, making it a premier radio- 

astronomy facility.  

2.7.1.4.3 Globus II Radar 

The Globus II is an AN/FPS-129  radar station located at in Vardø, Norway, near the Russian 

border.  The site is administrated by the Norwegian Intelligence Service and is used for: 1) to 

conduct space surveillance; 2) to conduct surveillance of areas of national interest abroad; and 3) 

to gather information of interest to research and development.  The radar was made by Raytheon 

37 

to collect intelligence data against ballistic missiles. It was relocated to Norway from 

Vandenberg AFB, CA where it had been titled “HAVE STARE.”  The radar, which uses a 

mechanically steered 27-meter dish antenna, is believed to have similar capabilities to the newer 

U.S. X-band radar used in the sea-based anti-ballistic missile system.  When the radar was built 

the Norwegians stated that it was going to be used to monitor objects in space such as satellites 

and space debris.  This information was to be added to the Space Catalogue orbital database 

provided by the US Space Command.   

Today, it is believed that Globus II has important roles in the U.S. anti-ballistic missile system 

and the maintenance of space situational awareness. Located near the Russian border it is highly 

capable of monitoring and building a signature database of Russian missiles. In addition, Vardø 

is well placed for the radar to collect precision data on the warheads and decoys carried by 

possible Russian, future Iranian missiles fired toward the U.S.  While the radar is administered 

by the Norwegian Intelligence Service, it is believed to be integrated within the U.S. SSN.  

2.7.1.4.4 Kwajalein Island 

The Ronald Reagan Ballistic Missile Defense Test Site, previously referred to as the Kwajalein 

Missile Range, is a missile test range in the Pacific Ocean. It covers about 750,000 square miles 

(1,900,000 km2) and includes rocket launch sites on multiple islands within Kwajalein 

Atoll, Wake Island, and Aur Atoll. It primarily functions as a test facility for U.S. missile 

defense and space research programs, and is under the command of the US Army Kwajalein 

Atoll, or USAKA.  The mission control center, along with most of the personnel and 

infrastructure, is located at the Kwajalein Atoll in the Marshall Islands.  The test site includes 

various tracking radars, stationary and mobile telemetry, optical recording equipment and a 

secure fiber optic data network via undersea cable. The Reagan Test Site also serves as a 

tracking station for manned space flight and NASA research projects.  Launch activities at the 

test site include ballistic missile tests, ABM interception tests, meteorological sounding 

rockets, and a commercial spaceport for SpaceX at Omelek Island.  The data received by the 

space capable sensors at Kwajalein Island can be used to augment the space situational 

awareness of the SSN. 

   

     Figures 43-45. Haystack Radar (L), Globus II Radar (C), and Kwajalein Radar Facility (R). 

38 

2.7.1.4.5 Sea-Based X-Band Radar 

The Sea-Based X-Band Radar (SBX) is a floating, self-propelled, mobile radar station designed 

to operate in high winds and heavy seas. It is part of the U.S. DoD Ballistic Missile Defense 

System.  The Sea-Based X-Band Radar is mounted on a fifth generation Norwegian-designed, 

Russian-built CS-50 semi-submersible twin-hulled oil-drilling platform.  It is nominally based 

at Adak Island in Alaska but can roam over the Pacific Ocean to detect incoming ballistic 

missiles. The platform is part of the Ground-Based Midcourse Defense (GMD) system being 

deployed by MDA. Being sea-based allows the platform(s) to be moved to areas where they are 

needed for enhanced missile defense.  The primary task of SBX will be discrimination and 

identification of enemy warheads from decoys, followed by precision tracking of the identified 

warheads.  The platform has a central, large dome that encloses and protects a phased-array, 

1,800 ton X-Band radar antenna.  Operating in the 7.0 to 11.2 GHz range, X-Band radar is also 

capable of contributing to SSA and the SSN mission by detecting, tracking, and cataloguing new 

LEO space objects. 

 Figures 46-47.  Sea Based X-Band radar during transport (L), and underway on own power (R). 

2.7.1.5 Infrared Tracking  

Infrared (IR) sensors can detect objects that emit heat.   As space is cold, on average about –200 

C, most objects in space are also cold. This limits ground and airborne terrestrial sensors that 

look up at ballistic missile payloads, satellites, and space debris from below with cold space as a 

background to the cold objects.  At best terrestrial IR sensors are limited to applications that 

track missile launches and track objects during re-entry.  To overcome this limitation of 

terrestrial IR sensors the U.S. and other major military powers have constellations of space-based 

IR sensors that look down in an effort to contrast the cold space objects against the hot terrestrial 

background.  These U.S. space based IR sensors are inputs to the integrated space situational 

awareness achieved by the SSN.   

39 

The Space-Based Infrared System (SBIRS) is a consolidated system intended to meet 

the U.S.'s infrared space surveillance needs through the first two to three decades of the 21st 

century. The SBIRS program addresses critical national needs in the areas of BMEWS early 

warning, missile defense, terrestrial battlespace characterization, and space situational 

awareness.  SBIRS will include satellites with IR sensors in GEO, IR sensors hosted on satellites 

in HEO, and ground-based data processing and control that ties SBIRS into the SSN.    

The SBIRS High will consist of four dedicated satellites operating in GEO, and sensors on two 

host satellites operating in a HEO. SBIRS High will replace the Defense Support Program (DSP) 

satellite constellation and was intended primarily to provide enhanced strategic and theater 

ballistic missile warning capabilities. The SBIRS Low program was expected to consist of about 

24 satellites in LEO. The primary purpose of SBIRS Low is the tracking of ballistic missiles and 

discriminating between the warheads and other objects, such as decoys, that separate from the 

missile bodies throughout the middle portion of their flights.  Its effectiveness comes again from 

the ability of those cold objects to be contrasted from above by SIBRS Low sensors against the 

background of a warm earth.  Interestingly, SIBRS High and Low are both optimal for detecting 

and characterizing cold space debris.  

Figures 48-49.  Artistic renditions of SBIRS Low (L), and SIBRS High (R). 

2.7.2 Russian Space Surveillance 

The Russian Federation Space Surveillance System (SSS) is a space situational awareness 

acquisition system that includes 10 radars operating in a combination of UHF, VHF, and C-Band 

of 4 to 8 GHz.  In a similar fashion as the U.S. SSN, the SSS integrates in multiple (12) optical 

and electro-optical facilities. The SSS radars are used to track objects in lower orbits, while the 

optical and electro-optical facilities are used only for tracking objects in higher orbits.  

Additional sensors are occasionally included in the system for important tasks and experiments. 

The lack of a worldwide network of sensors results in some major discontinuities in observation 

and some regions in Earth orbital space where objects cannot be observed at all.  Observations 

40 

are also provided to the SSS by two Anti-Ballistic Missile Defense (ABMD) radars in the 

Moscow region near Sofrino and Chekhov operating at 400 MHz in the UHF Band.  

Data from the sensors comes from approximately 50,000 observations daily to maintain a 

catalogue of nearly 5,000 objects, most in LEO, that are transmitted to the Russian Space 

Surveillance Center.  There they are processed, and the Russian Space Catalogue is updated and 

refined.  This includes updates on object identification, orbital elements, setting plans for future 

observations, determination of orbital lifetimes, and distribution of information to interested 

space programs.  Owing to geographical limitations similar to those in the U.S., Earth satellites 

at low inclinations are difficult or impossible to track.  As a whole, the SSS radar sensors appear 

to be limited to a range of about 4,000 km, not unlike the U.S. VHF Fence.   

Today, two sites appear to form the heart of the SSS in Russia, namely the Okno and Krona 

complexes.  By means of Okno and Krona Russia maintains a significant space surveillance 

capability independent of its Ballistic Missile Early Warning (BMEW) assets. These combined 

radar and electro-optical (EO) systems facilities have performed various military and civil roles, 

including an analysis of the surface impact point of the Mir Space Station and identification of 

space debris. The performance of Okno and Krona systems guarantees the Russian space 

surveillance network will play a valuable part to in both national defense and international space 

exploitation. 

2.7.2.1 Okna Facility  

The Okno system is a fully automated optical tracking station used for the detection, tracking, 

and identification of satellites.  Optical telescopes scan the night sky, while computer systems 

analyze the results and filter out the stars through analysis and comparison of velocities, 

luminosities, and trajectories. Satellites are then tracked with orbital parameters being calculated 

and logged.  Okno can detect and track satellites orbiting the Earth at altitudes between 2,000 

and 40,000 kilometers. This increased altitude capability over earlier space surveillance radar 

systems was necessitated due to the U.S. fielding surveillance satellites operating in high GEO. 

The Okno system is situated near Nurek, Tajikistan, approximately 50 km southeast of the 

capital of Dushanbe.  The main facility consists of ten telescopes covered by large clamshell 

domes. The telescopes are divided into two stations, with the detection complex containing six 

telescopes and the tracking station containing four.  Each station features its own control center, 

with a central command and control center, likely also housing the detection and tracking 

computer systems, located in the center of the facility.  Also present is an 11th, smaller dome 

mounted atop a much smaller building. It is not known what function this additional facility 

performs. It may contain guide-star-like atmospheric measuring equipment used to assess 

atmospheric conditions before activation of the system, such as that employed by the U.S. at the 

SOR and MSSS facilities. 

41 

Figures 50-51. Satellite image of Okno complex (L), and four tracking telescopes (R).. 

2.7.2.2 Krona Facility 

Like Okna, the Krona system combines long-range radar and optical tracking system designed to 

facilitate radar slew to EO cue.  Rather than simply identifying objects as artificial satellites, the 

Krona system seeks to categorize satellites by type.  The system consists of three main 

components: 1) a large S-Band phased-array radar for target identification; 2) a system of five X- 

Band parabolic radar antennae for target classification; and 3) an EO system combining a 

telescope with a laser system.  The Krona system has a range of 3,200 kilometers and can detect 

targets orbiting at a height of up to 40,000 kilometers.  Development of the Krona system began 

in 1974 when it was determined that current space-tracking systems were unable to accurately 

identify the type of satellite being tracked. Target discrimination was an important component of 

any ASAT program. Preliminary design work for the Krona complex, designated 45J6, was 

completed in 1976.   Installation of S and X-Band radar systems followed as did the EO/laser 

complex (designated as 30J6) with separate housings for the optical telescope and the laser 

system.  

The X-Band radar system incorporated into the 20J6 system was designed in part to provide 

telemetry data to direct the 30J6 optical/laser system. The laser system was designed to provide 

target illumination for the optical system, which would capture images of target satellites at night 

or in clear weather.  Favorable atmospheric qualities were one factor in determining the location 

of the Krona systems.  Construction of the first Krona facility began in 1979 near Storozhevaya 

in southwestern Russia.  

It was initially planned to construct three Krona complexes. The second Krona complex would 

have been located near the Okno complex in Tajikistan, with the third complex being located 

near Nakhodka in the Russian Far East.  

42 

    

      Figures 52-53. Krona tracking station (L), and 30J6 complex at Krona-Storozhevaya (R). 

 2.7.3 French Grande Réseau Adapté à la Veille Spatial 

The French Grande Réseau Adapté à la Veille Spatial (GRAVES)  is a space situational 

awareness radar employed by France for national security purposes.  Known in English as the 

Wide Network Suitable for Space Surveillance, GRAVES is designed to detect and characterize 

satellites operating in LEO.  GRAVES development began in early 1990, with its primary 

purpose being to provide France an autonomous capacity for the detection and/or identification, 

and cataloguing of satellites and objects like the U.S. Air Force SSN and Russian SSS, and to do 

so independently of those foreign systems.  GRAVES was commissioned in December 2005 and 

to date is the only operational satellite monitoring system in Western Europe.  Only Russia and 

the United States have similarly capable systems. 

The French acknowledge the need to maintain space situational awareness continuously and in 

real time from a national security perspective.  The French recognized the utility of the U.S. 

radar space fence composed of widely separated receivers across a distance between them that 

spans the length of the U.S., with the result being an electromagnetic curtain.  GRAVES serves a 

similar purpose, though with a different geometry.  

The GRAVES radar can detect satellites passing over France at orbital altitudes below 1000 km.   

In a similar concept to the U.S. PAVE PAWS phased array, GRAVES is a bistatic radar with 

electronic scanning and continuous emission active interrogation.  The receiving system 

measures the Doppler shift of the return signals.  Like the U.S. Space fence, the GRAVES 

transmitter site is located remotely from the receiver site.  The transmitter site is located on 

the former Broyes les Pesmes Air Base near the village of Broye-Aubigney-Montseugny.  The 

receiver site is located on the Plateau d'Albion roughly 400 km from the transmitter.  According 

to the Federation of American Scientists, the transmitting antennas of the GRAVES radar is 

VHF, operating at 143 MHz. 

43 

Figures 54-56.  GRAVES transmitter site (Top) and GRAVES receiver site (Bottom L and R). 

2.7.4 European Space Agency  

The European Space Agency (ESA) Space Debris Telescope is located at the Teide Observatory 

on the island of Tenerife, Spain. The telescope is ESA's Optical Ground Station forming a part of 

the Artemis Experiment. A large fraction of the telescope observation time is dedicated to space 

debris surveys, in particular the observation of space debris in GEO and in GEO transfer orbits.  

It was due to this dedicated task that the term ESA Space Debris Telescope became used very 

frequently.  Space debris surveys are carried out every month, centered, around the time of the 

New Moon.  The telescope is a Ritchey-Chrétien telescope with an aperture of 1 m and field of 

view of 0.7 degrees, and equipped with a cryogenically cooled mosaic CCD-Camera of 4k x 4k 

pixels. The detection threshold is between 19th and 21st magnitude, which corresponds to a 

capability to detect space debris objects as small as 15 cm in GEO. 

The partially ESA-funded Satellite Laser Ranging (SLR) global network of observation stations 

measure the round trip time of flight of ultrashort pulses of coherent light to satellites equipped 

with retro-reflectors.  This provides instantaneous range measurements of millimeter level 

precision which can be accumulated to provide accurate measurement of orbits and a host of 

important scientific data.  SLR is the most accurate technique currently available to determine 

the geocentric position of an Earth satellite.  The SLR network is also able to measure variations 

in the Earth’s gravity field over time.  SLR can also monitor the response of the atmosphere to 

seasonal variations in solar heating.  Finally, SLR provides a unique capability for verification of 

the predictions of the theory of General Relativity, such as the frame-dragging effect.  SLR work 

44 

is carried out at several global locations including Herstmonceux in East Sussex, UK, and 

Wettzell, Germany. The ESA funds SLR missions and the U.S. DoD has incorporated data 

obtained from this laser ranging into the development of their world surveying and measuring 

systems.   

Figures 57-58.  SDT on Tenerife Island, Spain (L), and SLR facility at Wettzell, Bavaria (R). 

2.8 Conclusions About Space Situational Awareness and Collision Avoidance 

In the 2010 report by the RAND report titled Confronting Space Debris - Strategies and 

Warnings from Comparable Examples Including Deepwater Horizon quoted earlier in this paper, 

RAND also observed:  

[Governments] argue that the problem is not severe enough now, though, to move to 

remediation, or actively removing debris, given the lack of government and private 

interest (particularly funding) for remediation efforts despite their increasing utilization 

of space. “If debris were deemed to represent an unacceptable risk to current or future 

operations,” they write, “a remedy would already have been developed by the private 

sector.”  

A few decision makers in government and industry say that there is still no current business case 

for cleaning up space debris, and the lack or infrequency of any serious or damaging collisions is 

evidence that debris concerns are overblown. The RAND report continues:  

The authors [of the RAND report], though, do provide some lessons for any future 

remediation efforts, using the saga of the Deepwater Horizon—the oil rig that was 

destroyed in the Gulf of Mexico in April, creating the largest oil spill in US history—as a 

case study. The biggest lesson, they argue, is that any remediation technologies need to 

be tested first in actual operating conditions, as many of the efforts tested on the 

Deepwater Horizon spill failed because they had not been previously used in deep ocean 

conditions. The event also demonstrated the need to have multiple approaches to solving 

the problem, as no single approach can work all the time. 

   

45 

The RAND report observations encourage an acceleration of debris clearing efforts to avoid the 

pitfalls of reacting to a disastrous forcing function.  The space domain is increasingly a global 

domain, just as international waters permit unrestricted access.  The sole early entrants were 

Russia and the U.S., and both continue to have the preponderance of operational space systems, 

laying claim to and filling up the best orbital altitudes.  With a focus on maintaining national 

security and commercial advantages in space, the best U.S. space situational awareness picture is 

not shared internationally.  The Russian SSS and French GRAVES are similarly compartmented 

for reasons of security.  So long as the global space situational awareness picture remains 

disintegrated serious gaps of coverage and object awareness will grow. 

As noted earlier, space situational awareness (SSA) is a critical prerequisite to understanding the 

advancing maturity of the Kessler Syndrome.  Without real time global SSA the risks of 

collisions are going to increase exponentially, in correspondence with the exponential rise in 

debris.  Collisions must be accurately predicted and avoided to preserve current and future 

orbital space systems. “Conjunctions” (orbital intersections of space objects) must be calculable 

with precision. Some advocates are calling for more accurate data, and suggest that 

USTRATCOM should make available the un-degraded SSA data calculated by the U.S. SSN to 

the global space community rather than the relatively inaccurate NORAD TLEs of today.  They 

echo the RAND report that in denying the larger space community more accurate data we risk a 

catastrophic event, and point to other parallels in recent history.   

One tragedy is noteworthy, as the combination of a threatening increase in object density in 

orbital space and inferior SSA data can be compared to the environment that contributed to the 

1983 shoot-down of Korean Air Lines Flight 007.  KAL 007 was a civilian airliner that was 

destroyed by Soviet interceptors on 1 September 1983, over the Sea of Japan.  It was intercepted 

after it strayed widely off of its planned New York City to Seoul, South Korea course, and into 

the restricted airspace of the Soviet Union near Sakhalin Island around the time of a planned 

Soviet missile test.  All 269 passengers and crew aboard KAL 007 were killed, leading to one of 

the tensest confrontations of the Cold War.  The Global Positioning System (GPS) existed at that 

time, but its use was restricted to the DoD.  As one consequence of the KAL 007 incident, on 16 

September 1983 President Ronald Reagan ordered the U.S. military to make the GPS available 

free of charge for civilian use so that navigational errors like that of KAL 007 could be averted in 

the future.  Unfortunately, this came as a result of tragedy and ensuing public outrage, not U.S. 

foresight.   

National security restrictions are realities we must live with.  Space faring nations who are also 

military powers will not want to compromise their secret advantages in SSA in spite of the rising 

debris threat.  In actuality, as little information as the U.S. Air Force shares regarding its SSN 

data collection and catalogue, it actually provides more information than other national security 

establishments.  In contrast, the U.S. provides timely precision warning to the ISS and 

commercial satellites that the SSN tracks.  Also, the USSTRATCOM provides the North 

American Aerospace Defense Command (NORAD) two line elements (TLE) to the public and 

industry for general purposes.  If in a coordinated effort the U.S. and perhaps the Russians could 

agree, perhaps USSTRATCOM could reduce the error probability in published TLEs by some 

percentage the Russians could do similarly with their SSS TLEs as an initial step towards better 

46 

SSA. 

Still, such efforts to change national policies require time and do not guarantee useful outcomes.  

Since NORAD TLEs contain large probabilities of error that prevent potential U.S. adversaries 

from knowing the true precision of the SSN SSA capabilities strong resistance to change is 

assured, in spite of the change in context.  This decision to provide the public erred TLEs was 

considered a risk worth taking when the Earth orbital space regime was less populated and less 

polluted with debris.  Collisions were highly improbable so decision makers were satisfied that 

the public was not placed at risk.  Unfortunately, today orbital space is a much more crowded 

and hazardous environment, and all users of space are badly in need of higher precision data to 

avoid collisions.  Therefore, two efforts must proceed concurrently.  First, the value of better 

SSA must be articulated.  Second, space users must independently develop a work-around to get 

more accurate data now as the increasing risk of collisions represents a clear and present danger.   

As for value, insurers are currently mixed in their evaluation of debris as a threat that requires 

higher operator premiums.  Some insurers tend to charge more for that threat than other.  

However, it is generally accepted that the threat is increasing.  In the future insurers of spacecraft 

might welcome reduced risk to the space asset they underwrite.  Even more so, space systems 

operators might welcome a reduction in the insurance premiums that they are charged.  As 

evidence, on 18 March 2011 at the Congressional Aerospace Policy Retreat a presentation titled 

“Space Debris and Insurance” was briefed by Chris Kunstadter, the Senior Vice President of XL 

Insurance.  On a slide titled "Basic Space Insurance Market Metrics" he stated: 

[There are] 30-40 insured launches per year (~50% of total) carrying 20-25 GEO 

satellites and 15-30 LEO satellites.  Insured values range up to $400 million (up to $700 

million for Ariane dual launches), typically $100 million to $250 million.  Annual 

premium ranges from $750 to $950 million.  Annual claims range from $100 million to 

$1.8 billion.  Currently 193 insured satellites [are] in orbit [for a] Total insured value of 

$19.8 billion.  GEO: 175 satellites = $18.5 billion (~50% of total).  LEO: 18 satellites = 

$1.3 billion (~5% of total).  Hundreds more insured for third-party liability. 

At the same time, the space team has determined that there may be a monetary cost that can be 

assigned to degraded data, specifically the cost that operators incur from debris-related damage 

and destruction over the course of the lifetime of representative space system constellations.  

Again, as evidenced at the aforementioned Congressional Aerospace Policy Retreat, in another 

presentation titled “Orbital Debris: Human Created Barriers to Space,” Aerospace Corp. 

analyzed projections of the cost of debris on representative satellite constellations for a 30 

timeframe.  The analysis found:  

[1] A small constellation (5 satellites) of government weather satellites with a lifetime of 

about 6 years.  [2] A medium-sized (20 satellites) constellation of commercial Earth 

imaging satellites with a lifetime of about 9 years.  [3] A large constellation (70 satellites) 

of commercial communications satellites with a lifetime of about 12 years.  Increase of 

between $700M and $1.2B in constellation replenishment costs for these hypothetical 

constellations. 

47 

Another cost would seem to be incurred from operators responding conservatively to error-filled 

data, and consequently making unnecessary spacecraft maneuvers in a dense object environment.  

Each maneuver expends fuel and shortens the operational lifetime of the satellite.  When 

calculated over the lifetime of the satellite individual maneuvers can cost millions of dollars per 

event, particularly for massive satellites that need to maneuver in GEO.   

Conversely, more accurate data has an inversely proportional value.  More accurate data leads to 

lower probabilities of error in predicted missed distances and fuel and system lifetime are 

conserved.   

In addition to the monetary value of better data the space team has identified a normative, better 

said altruistic value.  There should be a shared incentive to avoid a catastrophic tragedy, 

especially when it can be predicted in advance, and is not acted on.  The BP oil spill and KAL 

007 flight path deviation are examples that led to public forcing functions that forced changes 

based on public outrage rather than foresight.  As for space, the collision between Iridium and 

Cosmos satellites was a taste of the expensive possibilities.  Loss of GPS and certain GEO 

systems would be even more costly, perhaps seriously upsetting terrestrial civil capabilities in the 

process.  Blackouts and transportation interruptions cannot be ruled out, much less loss of 

internet, navigation and other communications capabilities.  At the extreme end of the spectrum 

is the possibility for loss of life in orbit or on Earth. 

As for an independent work-around, a catastrophe of the sort described above has not yet 

happened, and it would appear that the space community still has a chance to get in front of the 

issue in a preventative fashion.  The story of Differential GPS is instructive as it has similarities 

with the TLE accuracy dilemma.        

Differential GPS (DGPS) is an enhancement to GPS that provides improved location accuracy, 

from the 15-meter nominal GPS accuracy up to about 10 cm.  When GPS was first being put into 

service, the U.S. military was concerned about the possibility of enemy forces using the globally 

available GPS signals to guide their own weapon systems. To avoid this, the precision signal was 

encrypted.  The publicly available signal was deliberately degraded, just as the NORAD space 

TLEs are degraded today.  The degraded GPS public signal was known as "Selective Availability 

(SA)," and was useless for any serious navigation purposes.  It even proved dangerous when 

during the Gulf War widespread use of civilian receivers by U.S. forces causing position errors 

of up to 100 meters.  SA threatened to bring greater harm to U.S. forces than if it were turned off.  

Government enforcement of SA persisted into the 1990s, so users in need of high position 

location data turned to the independently available DGPS work-around to great satisfaction, as it 

had evolved into a more accurate capability than the encrypted military signal.    DGPS was a 

positive forcing function that helped lead to President Bill Clinton’s decision to turn the military 

encryption and SA signal off permanently in 2000. 

Independently, experts at the NASA Ames Research Center have studied the deficiencies of 

publicly available TLE data and asked the following questions: 1) Can we calculate more 

accurate a more accurate real time SSA using the degraded public data, and 2) Can we predict 

48 

conjunctions using only public TLEs well enough to make practical collision avoidance / space 

traffic management decisions?  On 11 February 2010 Creon Levit and Will Marshall of the 

NASA Ames Research Center coauthored a paper titled Improved Orbit Predictions Using Two- 

Line Elements.  In the paper Abstract the authors stated in part:  

This paper addresses collision avoidance, by describing a method that contributes to 

achieving a requisite increase in orbit prediction accuracy.  Batch least-squares 

differential correction is applied to the publicly available two-line element (TLE) catalog 

of space objects. Using a high-precision numerical propagator, we t an orbit to state 

vectors derived from successive TLEs. We then propagate the fitted orbit further forward 

in time. These predictions are compared to precision ephemeris data derived from the 

International Laser Ranging Service (ILRS) for several satellites, including objects in the 

congested sun-synchronous orbital region. The method leads to a predicted range error 

that increases at a typical rate of 100 meters per day, approximately a 10-fold 

improvement over TLE's propagated with their associated analytic propagator (SGP4). 

Corresponding improvements for debris trajectories could potentially provide initial 

conjunction analysis sufficiently accurate for an operationally viable collision avoidance 

system. 

  

The authors go on to discuss additional optimization and the computational requirements for 

applying all-on-all conjunction analysis to the entire current TLE catalog, and to future catalogue 

entrants.  The authors conclude by outlining a scheme for debris-debris collision avoidance that 

may become practicable given these developments. 

The scientists at NASA Ames have also conceived of complementary efforts that can assist in 

refining the SSA common operating picture with existing sensor technologies.  Creon Levit has 

suggested that amateur space enthusiasts and research institutions can be incentivized to 

purchase small VHF receivers that capture the Air Force fence radar returns continuously and 

directly.  The fence transmission frequencies are known, and in a form of crowd-sourcing those 

distributed inputs can be synthesized in real time for increased accuracy.  Just as millions of 

personal computers have participated as netted, parallel contributors to massive research 

problems by conducting calculations invisibly in the background, the same can be done for SSA.  

These 24/7 received VHF returns can, via internet contribute to an ever-more refined space 

object data base that is not under the control of USSTRATCOM.  Space systems operators and 

insurers might subsidize or provide small receivers for free due to the commercial value of 

superior SSA.  The space team predicts that space enthusiasts can be predicted to benefit from 

the great normative satisfaction of contributing to the future of space.  A company such as Radio 

Shack might be willing to assist with distribution as provision of the cheap or no-cost receivers 

would draw many customers to their stores.  NASA Ames noted that the much touted but long 

delayed S-Band upgrade to the Air Force Fence may be unnecessary as the products of the batch 

least-squares differential corrections may be superior to the higher resolution promised by S- 

Band.  Here again is a one-for-one analogous repetition of the DGPS example described above.  

Finally, Creon Levit has noted there should be a concurrent software development effort to keep 

pace with the improvements via TLE differential corrections.  The corrections are admittedly 

computationally intensive, although the NASA Ames super-computing capacity to do such 

49 

processing is more than able to handle the increased load.  Nevertheless, improved software 

would permit even more efficient use of the computational resources.       

Other groups outside of the national security space communities have also taken the initiative to 

provide better data for collision avoidance.  For example, “What’s Up” is the title of a useful 

website at http://www.satellitedebris.net/whatsup/.  What’s Up is a visual data base for satellites 

and debris that combines database information from the U.S. SPACETRACK catalog and the 

UCS Satellite Database, and presents it visually in Google Earth.  It allows the user to display the 

location of individual objects or sets of objects (both active satellites and debris) around the 

Earth, as well as showing the orbit and technical information about each object. The user can 

also change the color of sets of objects to distinguish them in the display. The location and orbits 

of each object are updated every morning from the SPACETRACK catalog and are downloaded 

to the user’s computer.  Another example is the Space Data Association (SDA), which has a 

website at http://www.space-data.org/sda/.  The SDA is a non-profit association that brings 

together satellite operators who value controlled, reliable and efficient data-sharing critical to the 

safety and integrity of the space environment and the RF spectrum. The SDA was founded by 

Inmarsat, Intelsat and SES, three of the leading global satellite communications companies. 

2.9 Gaps in Space Situational Awareness and Debris Removal Efforts 

Estimates on the number of human-made and potentially damaging space debris and objects 

currently in orbit range from 500,000 1 cm or greater in size to tens of millions of objects less 

than 1 cm.  All are potentially damaging to satellites, many with predictably catastrophic results.  

In spite of the SSA systems such as SSN, SSS, and GRAVES the objects between 1 mm and 10 

cm escape detection.  Increased resolution over time will improve certainty, but for the time 

being exact locations cannot be determined.  Scientists are in agreement that the debris field 

continues to be populated faster than the rate of debris reentry.   

Resolution and SSA issues aside, the growing danger of collisions between massive detectable 

objects is a call to action for orbital debris removal (ODR) of those objects.  There is also a 

consensus that a single collision between two satellites or large pieces of “space junk” will send 

(and have recently sent) thousands of new pieces of debris spinning into orbit, each capable of 

destroying further satellites.  Some scientists have speculated that the threshold of a runaway 

Kessler Syndrome has already been crossed in polar orbits where satellites converge, and that 

exponential debris self-proliferation / growth is underway.   

A further aggravation of the problem is lacking international accountability.  The dominance of 

“clean orbits” in LEO and MEO, especially by legacy space powers, suggests responsibility be 

assigned to them for the ODR from polluted orbits, orbits that they were solely responsible for 

polluting in the past.  Today many of those LEO orbits between 800 km and 1,000 km and 

between 1,400 km and 1,600 km are nearly unusable due to the higher risk of collisions.  

Clearing and opening up the polluted orbits would permit current and pending new entrants to 

space to plan and execute missions of interest to their nations.  In addition to existing space 

faring nations who would appreciate new clean orbits, cash rich new entrants could include, but 

are certainly not limited to the United Arab Emirates, and Brazil and Saudi Arabia in the future.   

50 

In the U.S. NASA already has a program dedicated to understanding and mitigating space debris.  

However NASA cannot do it alone.  At a minimum the U.S. (Air Force) Executive Agent for 

Space in DoD should demonstrate accountability, and fund technologies and systems to 

eliminate debris in unusable orbits, the pollution of which the U.S. is partially or fully 

responsible.  This DoD initiative should be taken in the spirit of the U.S. demonstrating 

international responsibility and cooperation in space matters.  On the other hand if the U.S. DoD 

does not take the initiative, the UAE, Saudi Arabia, China, and other cash rich nations might 

unilaterally fund efforts to clean up those orbits on their own, and for their own benefit and use.  

The Japanese have already begun such work with a “fishing net” based concept, to be discussed 

later.  There are other several viable commercial technologies for debris collection and removal 

that only lack funding for full realization.   

In 1976, when NASA scientists first identified the debris risk, they predicted that space collisions 

would happen once a century.  Four occurred over the next four decades. Today the agency 

predicts four collisions every 20 years. Former NASA scientist Don Kessler, who discovered the 

debris amplification process with former NORAD senior analyst John Gabbard, foresees a 

catastrophic collision once every 20 years. Even NASA recognizes that its existing rule, namely 

that objects must have the capability to push themselves (or be pushed) out of orbit within 30 

years of launch, isn’t enough anymore. Earlier this year, it published a paper showing that it 

could make low-Earth orbit safe by removing five objects per year.   

To collect ideas on how to achieve this, last year NASA and DARPA, the DoD’s research arm, 

gathered hundreds of engineers and scientists for the first-ever International Conference on 

ODR. Nearly all the solutions discussed there rely on finding some way to de-orbit the debris so 

it burns up in the atmosphere. The conference also revealed that international cooperation is the 

greatest hurdle. There is, for example, no official consensus on what constitutes space debris.  

One country’s seemingly dead satellite might just be hibernating for future use. Governments 

were also concerned that debris-removal systems could have military uses, and not every country 

provides details about what they have in orbit.   

Concurrently, NASA stood up an Orbital Debris Program Office.  The office located at 

the Johnson Space Center which has been assigned as the lead NASA center for orbital 

debris research. Since its formation the NASA Orbital Debris Program Office has taken the 

international lead in conducting measurements of the environment and in developing the 

technical consensus for adopting mitigation measures to protect users of the orbital environment. 

Work at the center continues with developing an improved understanding of the orbital debris 

environment and measures that can be taken to control its growth.  As noted earlier NASA Ames 

Research Center has also begun to make significant contributions to NASA’s efforts.  Orbital 

debris research at NASA is divided into several broad research efforts, involving modeling, 

measurements, protection, mitigation, and reentry of orbital debris.  Protection and reentry were 

discussed earlier in this paper.  What follows is a discussion of the various kinetic and 

electromagnetic avoidance and removal concepts that have been developed by NASA or  

presented to NASA to-date.  

51 

2.9.1 Orbital Debris Removal Concepts  

Amateur astronomers and space enthusiasts worldwide can also contribute to collision avoidance 

efforts.  Specifically, amateurs can contribute by filling gaps and independently making and 

reporting objects and phenomena of potential interest.  Amateur discoveries of comets and 

asteroids are reported in the media fairly routinely.  As for space debris there is a significant 

opportunity for amateurs globally to contribute to the shared picture of orbital Earth.  Space 

enthusiasts worldwide can potentially be incentivized to search NASA space imagery archives or 

the night sky in real time in order to make new discoveries, and/or confirm previous 

observations.  Naming debris and asteroid objects after the discoverers, paying discoverers for 

new object discoveries, and even X-Prizes for technological designs that lead to the actual 

mitigation of debris to clean up the most polluted orbits are all worthy of consideration.   

2.9.1.1 Electrodynamic Tethers 

Electrodynamic tethers (EDTs) are long conducting wires which can operate on electromagnetic 

principles as generators by converting their kinetic energy to electrical energy, or alternatively 

converting electrical energy to the kinetic energy in the form of a motor.   Electric potential is 

generated across a conductive tether by its motion through the Earth's magnetic field.  As part of 

a tether propulsion system, crafts can use long, strong conductors to change the orbits of 

spacecraft.  It is a simplified, very low-budget magnetic sail. It can be used either to accelerate or 

brake an orbiting spacecraft. When direct current is pumped through the tether, it exerts 

a Lorentz force against the magnetic field, and the tether accelerates the spacecraft. 

A motional Electromotive Force (EMF) is generated across a tether element as it moves relative 

to a magnetic field.  It is assumed the tether system moves relative to Earth’s magnetic field.  

Similarly, if current flows in the tether element, a force can be generated that is orthogonal to the 

path of both the direct current path through the conductor and the lines of magnetic force that the 

tether crosses.  In self-powered mode, this EMF can be used by the tether system to drive the 

current through the tether and other electrical loads, to emit electrons at the emitting end, or 

collect electrons at the opposite.  The self-powered mode will cause the perigee of the spacecraft 

to be lowered in altitude as the velocity slows.  There atmospheric drag will take over and 

rapidly de-orbit the spacecraft.  Conversely, if the system is in boost mode, on-board power 

supplies must overcome this motional EMF to drive current in the opposite direction, thus 

creating a force in the opposite direction.  This will increase the velocity of the spacecraft and 

over time drive the system to a higher orbital altitude.   

52 

Figures 59-60.  Electrodynamic tether boost and de-boost forces (L), and deorbiting tether (R). 

There are several tether developers who have made proposals and even conducted successful 

experiments in support of NASA.  One commercial proposal is employed here as a 

representative concept.  It has been selected for its public domain availability, and its inclusion is 

not intended to indicate a preference for one concept over another.  On 10 February 2010, 

Jerome Pearson, Eugene Levin, John Oldson, and Joseph Carroll of Star Technology and 

Research, Inc. and Tether Applications made a presentation titled “ElectroDynamic Debris 

Eliminator (EDDE) for Safe Space Operations” before the 13th Annual FAA/AIAA Commercial 

Space Transportation Conference.  The presentation focused on the EDT product.  For the 

purpose of discussion below, “EDDE” has been replaced with “EDT” for neutrality, yet to 

demonstrate the general maturity of existing EDT concepts by showing what one proposer has 

presented.   

The presentation began with the illustration of all the man made debris mass orbiting earth, 99% 

of the mass and 98% of the surface area of all those debris is still concentrated in a mere 2,465 

objects, each having a mass of 2 kg or greater.  This concentration represents the possibility to 

clean up LEO in the near term, given effective technologies.  If the removal of all 2,465 objects 

over 2 kg from LEO, future collision-generated LEO debris can be accomplished, it would be 

reduced by 99%, effectively preventing the Kessler Syndrome debris runaway / proliferation 

from occurring.  The ideal technology must focus on capturing the 2,465 objects of  >2 kg mass 

and cause each to be de-orbited in a controlled de-boost.  EDT generally, and EDT specifically 

were introduced as hopeful technologies. 

In the process of orbital cleanup operations, the EDT must actively avoid all tracked satellites 

and debris.  The EDT vehicle must also enable targeted precision re-entry if that is required.  

EDT vehicles could eliminate the threat of future collision-generated debris in LEO over a period 

of 7 years.  This could also include the start of a regular service that removes all newly launched 

upper stages and failed satellites. 

53 

The electromotive force (EMF) that is imposed on the tether that can drive the EDT to higher 

and lower orbital altitudes, and amounts to “Propellantless Propulsion.”  The principle has been 

demonstrated in practice in orbit by NASA-JSC on JSC’s Plasma Motor Generator (PMG) flight.  

Each EDT is only 100 kg, and stows into 24” by 24” by 12” volume.  In fact two EDTs fit into 

one ESPA secondary payload slot.  Each net manager holds 100 50 gram mesh nets.  When the 

EDT passes the target at 2-3 meters per second it can capture the object in the net, while 

damping out capture dynamics. 

Figure 61.  EDT boost and/or de-boost vehicle (courtesy: Star Inc.). 

EDT can perform 100’s of kilometers per day in altitude changes, and over one degree per day in 

orbital plane changes.  As an incremental approach, a “Mini-EDT” demonstration could be 

performed first as a proof of concept.  This demo system could be launched as a piggy back 

payload on any flight with 100-kg margin.  Once in space it could capture and drag down an 

inactive U.S. object.  For example, a Pegasus Upper Stage could serve as the captured object.  A 

scaled-down mission-capable EDT could also be employed to demonstrate orbit transfer and 

rendezvous capabilities, again using a Pegasus Upper Stage as the sample object in place of an 

operational satellite. 

EDT is also capable of removing debris to higher, non-interfering graveyard orbits for storage in 

anticipation of future recycling in salvage operations.  Alternatively, EDT can lower debris to a 

330 km altitude orbit for rapid natural decay, and with a “smart drag” device a controlled reentry 

could better guarantee a precision and safe impact on land or at sea.  Release to targeted reentry 

point could use the momentum exchange between the EDT and the debris object.  This principle 

was demonstrated by SEDS-1 by the U.S. and by YES-2 during a joint ESA and Russian 

mission. 

  

The EDT capability fits well with emerging concepts and plans for international space traffic 

control EDT is the first of a new class of space vehicles that is designed to roam over and 

throughout LEO like a Unmanned Arial Vehicle (UAV) in controlled air space.  It is designed to 

cross satellite orbits while avoiding collision, based on real time space situational awareness and 

coordinated flight plans for safe navigation. During typical debris removal operations EDT 

would drag each captured object below the 330 km altitude of the ISS, thereby reducing its orbit 

life to a few months.  In fact each EDT vehicle could remove 40 tons per year from LEO, or 400 

times its own mass per year.  In the end all of the 2,465 objects over 2 kg (2166 metric tons total) 

currently in LEO could be removed by 12 EDTs over a period of just 7 years. 

54 

Figures 62.  Errand satellite with de-boost / de-orbiting electrodynamic tether attached. 

2.9.1.2 Combining Kinetic and Electromagnetic ODR  

EDTs from Star Inc. and other manufacturers appear to be sufficiently mature to be integrated in 

all new space vehicles or components that find themselves in orbital space.  As for existing 

debris, it is critical to note that the economical role of tethers is primarily in de-orbiting larger 

pieces of space debris, including non-operational satellites.  These objects currently number in 

the low thousands and can be located and characterized with great precision so that robotic 

systems could approach them and attach de-orbiting tethers.  As for smaller, less massive objects 

such as those in the size range of 1 – 10 cm, those objects are better suited for other ODR 

techniques, most notably high energy lasers (HEL).  Tethers and lasers are therefore completely 

complementary technologies with respect to addressing the orbital debris challenges.  Directed 

energy (DE)-enabled ODR is discussed in the next section.    

2.9.1.3 High Energy Lasers 

DE engagement of debris provides an instantaneous capability to protect spacecraft and satellites 

55 

from destructive hypervelocity collisions with debris.  In LEO debris is closing with spacecraft at 

up to 10 km per second and poses the greatest threat to spacecraft today according to NASA.  

There are several advantages to high energy laser (HEL = / > 1 kW average power) ODR and 

collision avoidance techniques: 1) the momentum of laser beam photons imparted to the object at 

the speed of light can be used to produce  thrust on the debris directly.  While this photon 

pressure would be miniscule, it may be enough to nudge small debris into new orbits that do not 

intersect those of working satellites, achieving collision avoidance.  2) another laser induced 

cause of thrust can come from debris out-gassing when that object is thermally loaded during 

prolonged exposure to a high average power laser; 3) finally, high energy pulse lasers are 

capable of ablating the surface of the engaged debris causing momentary acceleration from high 

velocity plasma jet forces.   

One proposed concept that NASA has considered is the “Laser Broom.”  The laser broom 

concept is based on a powerful multi-megawatt ground-based HEL designed to ablate the front 

surface off of debris and thereby produce a rocket-like thrust that slows the object. With a 

frequently repeated application the debris will eventually decrease in altitude enough to become 

subject to atmospheric drag.  In the late 1990s, US Air Force worked on a ground-based laser 

broom design under the name "Project Orion” as a means to remove fragments from 1 - 10 cm in 

size is the laser broom, a proposed multi-megawatt land-based laser that could be used to target 

fragments. When the laser light hits a fragment, one side of the fragment would ablate, creating a 

thrust that would change the eccentricity of the remains of the fragment until it would re-enter 

harmlessly. A laser broom is a proposed ground-based laser beam-powered propulsion system 

whose purpose is to sweep space debris out of the path of other artificial satellites such as the 

International Space Station.  Lasers are designed to target debris between one and ten 

centimeters in diameter. Even small-sized debris can cause considerable damage in extremely 

high-speed collisions.  The laser broom is intended to be used at high enough power to punch 

through the atmosphere with enough remaining power to ablate material from the debris for 

several minutes.  Intensive laser energy would also would impart a small thrust to alter 

the orbit of orbital debris, ostensibly dropping the perigee into the upper atmosphere, thereby 

increasing drag so that the debris would eventually burn up on entry into the Earth atmosphere.  

Recent NASA research (2011) indicates that firing a lower power HEL beam at a piece of space 

junk could alter velocity by 1.0 mm per second.  Keeping it up for a few hours per day could 

alter its course by 200 m per day.   

In 2011 scientists at NASA Ames Research Center proposed that lower power ground-based or 

space-based HELs could also perturb orbits and nudge small debris to higher or lower altitudes 

so they would de-orbit quicker, or avoid a predicted collision.  Again, the NASA Ames concept 

targets smaller space debris that are not suited physically or economically for removal by kinetic 

means.  The advantages of the lower power HEL its immunity from being classified as an anti- 

satellite (ASAT) weapon and a lower likelihood of unintended damage to functional space 

systems.  The most promising laser concepts for ODR are discussed below: 

2.9.1.3.1 Laser Orbital Debris Removal  

In a 2 February 2002 presentation titled “Laser Orbital Debris Removal (LODR),” the President 

of Photonic Associates discussed the Photonics LODR concept.  The presentation noted that a 

56 

LODR concept engineering validation study was funded by NASA in 1996.  Based on that study 

NASA concluded that: “The capability to remove essentially all dangerous orbital debris in the 

targeted size range is not only feasible in the near term, but its costs are modest relative to the 

likely costs to shield, repair or replace high-value spacecraft that could otherwise be lost due to 

debris impacts for debris particles greater than about 1cm in size.” The study concluded that in 

1996 dollars less than $200M was required to field a LODR system capable of clearing 80% of 

LEO debris over a period of two years.  

By employing LODR, target access is speed-of-light, multi-tasked, redundant and agile.  Unlike 

kinetic ODR concepts, new debris created by LODR are microscopic.  The ablation depth per 

pulse is a few monolayers, so the total mass removed is small, however with a jet velocity of 

10.7  km/s.  LODR also exhibits system multi-applicability, as it can address challenges in LEO, 

MEO and GEO in the form of divert-to-protect applications.  By causing the ablation jet to push 

“back” or “up” on the object will cause the object to enter a lower perigee by slowing or 

distorting the eccentricity of the orbit.  The objective is to cause the object to be forced into a 

lower perigee of 200km or less.  For LEO objects this is typically achieved by adding a ∆V of - 

150 m/s.   By employing LODR many small objects in LEO can be forced to re-enter in one 

pass.  The ablation plume is normal to the heated surface of the debris, independent of laser 

beam incidence angle.  Also, targets at altitude are tumbling, and stationary objects will be 

caused to spin by laser strike.  However, the time-average plume thrust vector of a rotating target 

over many shots of a 100 Hz pulse train favors the direction from which the laser beam arrived 

over time.  

LODR engagement is a three step process.  In Step 1 SSN data provides sufficient cuing 

information so that wide field-of-view (FOV), solar-illuminated survey instruments can optically 

capture the object and establish ephemerii.  In step 2 a precision, active day or night optical 

tracker having a narrow FOV system takes over to allow range-gating & parallel processing.  

The MSSS and SOR LIDAR capabilities are good representatives of this capability.  In Step 3 

the target debris is handed off to the LODR short pulse “pusher laser” for engagement multiple 

close succession engagements (100 Hz typical).  Post engagement measurements are then taken 

using SLR and engagements are repeated on subsequent orbital passes as required until the 

object has been satisfactorily “nudged” in such a way as to avoid an otherwise predicted 

collision. 

57 

Figure 63-64. Large beam director (L) projecting short pulse laser for surface ablation (R). 

2.9.1.3.2 Free Electron Laser 

In December 2009, R. Whitney & G. Neil of Thomas Jefferson Lab, S. Biedron and J. Noonan 

Aargon National Lab, and J. Lewellen of the Naval Postgraduate School presented a concept for 

orbital debris removal at the International Orbital Debris Removal Conference titled  Directed 

Energy –Orbital Debris Removal.  The purpose of the presentation was to introduce the 100 kW 

– MW class average power Free Electron Laser (FEL) as a candidate capability to rapidly clean 

all LEO altitudes of orbital debris.  Much of the following discussion is derived directly from the 

referenced presentation.  The use of a 100 kW – MW-class Free-Electron Laser (FEL) based 

Directed Energy (DE) source for high energy laser Orbital Debris Removal (ODR) has many 

general advantages which make it conducive to integration with short pulse LODR: 

        Figure 65. Free Electron Laser generates coherent light from undulating electron beam. 

The most important FEL advantage is the tunability of a single FEL DE source in real time and 

across an operationally significant band of the mid IR, near IR, visible light, and near ultraviolet 

(UV) spectrums.  Due to FEL tunability a single FEL source can be optimized in real-time for 

maximum atmospheric transmissibility during debris engagements, based on local ground-to- 

space propagation windows at the time of engagement.  When combined with adaptive optics 

58 

that compensate for atmospheric turbulence the high average power FEL provides the most 

efficient means of transmitting laser energy to space in support of ODR.  The FEL can also serve 

to act as a guide star laser in support of a coaxial high energy short pulse laser, such as the 

LODR in the previous discussion.  

The FEL micro pulse train couples with debris more effectively.  Another benefit of the FEL 

over other laser sources is the unique optical beam structure.  The FEL beam, as a function of the 

unique manner in which the optical beam is generated, is composed of a long, yet variable train 

of micro pulses having a pulse duration of approximately 500 to 1,000 femtoseconds at the 

aperture at a rate of up to 75 MHz.  During transmission to space those pulses will elongate to a 

pulse duration of approximately one nanosecond each and upon arriving at the debris object will 

be quasi-CW.  In addition to exerting photon pressure, the FEL can thermally load the target, 

cause propulsive out-gassing, and potentially vaporize the material.  Together these FEL counter- 

thrust generating effects will slow the velocity of debris. 

The FEL design is free of these lasing medium thermal management issues, and the FEL can 

therefore lase continuously, as necessary.  The FEL optical resonator is a vacuum and has 

significant advantages when compared to other all-electric alternatives.  Solid State lasers must 

dissipate accumulated heat efficiently if they are to achieve sustained short pulse operation 

without suffering damage due to an unsuitable duty cycle.  A cryoplant is required to cool 

Helium for the operation of the linear accelerator (LINAC) that is integral to the FEL, however 

this too is electricity powered.  During operation the only cooling that is required is for the 

resonator mirrors, to prevent their distortion. One can turn the FEL on and leave it lasing 

indefinitely as long as the precision and endurance of the cooled resonator mirrors hold out - this 

is why high average power FELs are suited to power beaming.   

For these reasons the FEL and solid state LODR systems are ideally suited for integration into a 

single, combined effects LODR that exhibits the best qualities of both.  Two variations of high 

average power FEL generation are pictured below, namely the recirculating oscillator and 

amplifier designs.   

        Figure 66-67. FEL light generation using oscillator design (L), and amplifier design (R). 

59 

FEL technology today is mature, and now scalable from 10kW to 100kW for early 

demonstrations and iterations of LODR.  If power beaming is desired as a future additional 

capability of a FEL-LODR site, FELs will have MW-class capabilities within a decade. 

2.9.1.3.3 Combining LODR Short Pulse and High Average Power FEL in Single System 

The proposed LODR short pulse ODR laser and the FEL high average power ODR laser are well 

suited to complimentary integration within a single ground-based LODR system.  The high peak 

power short pulse system is better suited to the debris surface ablation/counter thrust capability 

that has always been the touchstone of LODR.  Likewise the FEL is perhaps better suited to 

LIDAR imaging, longer dwell time for thermal loading and vaporization, guide-star operation, 

ranging, and dual functionality for power beaming, perhaps for relay mirror-equipped high 

altitude airships or for powering orbital robotic tugs during periods of darkness.  Systems 

integration would permit them both to be projected through the same large beam director 

aperture.  Both lasers and the selected optics can be optimized for the best ground to space 

wavelength in the range of 265-nm to 4 μm.  Together the two distinctive lasers could combine 

their advantages cover the spectrum of ground to space applications is support of ODR. 

Combined LODR systems could be located at relatively high elevations in Arizona, Hawaii, 

Atacama Chile, Australia, the Mideast, and / or other suitable sites near the South and North 

Poles to minimize atmospheric disturbances for the light.  All LODR sites would be 

internationally manned, and each engagement of sequence of engagements would be coordinated 

through relevant national Laser Clearinghouses, most importantly those of Russia, China, and the 

U.S.  With respect to research and development, high average power FEL can leverage the U.S. 

Navy investment in scaling up the average power capability of FEL.  Likewise, short pulse 

LODR can leverage the extensive funded short pulse R&D being conducted at the U.S. 

Departments of Energy and Defense (DoE and DoD).   

In support of LODR, another critical R&D effort that can be conducted concurrently is laser 

effects experimentation.  The DoE has exceptional user FEL user facilities at which FELs and 

short pulse lasers could be experimented with side-by-side.  Measurements related to LIDAR 

performance, vapor thrust from out-gassing, jet thrust from surface ablation, glint, 

melt/vaporization rates and other factors could be taken.  Both laser types could engage 

magnetically or electrostatically floating coupons that are representative of real debris floating in 

vacuum. 

60 

Figure 68.  Combining high average power FEL and high energy short pulse lasers in LODR. 

2.9.1.3.4 NASA 10 kW Average Power Solid State Laser 

On 10 August 2011 the GSP-11 Space Team received a presentation coauthored by NASA 

employees Chris Henze, Will Marshall, James Mason, Jan Stupl, and Creon Levit  of the Ames 

Research Center.  The title of the brief was “Space Debris Research Activities at NASA Ames 

Research Center.”   The brief began by asking what technique is most hopeful for slowing or 

stopping the runaway Kessler phenomenon that may have already begun in polar orbits.  The 

brief questioned whether the publicly available Two Line Element (TLE) data is sufficient for 

calculating the risk of collisions for practical global collision avoidance / space traffic 

management. The brief concludes that kinetic mitigation means such as timely reentry and 

removal of non-functional satellites to graveyard orbits is not enough in the near term.  The 

number of actual major collisions in 2011 follows an even more severe curve than the average 

predicted by Kessler in 1978.  Also, Active Debris Removal (ADR) by kinetic means such as 

tethers, tugs, etc. did not appear to be economical, and conceptually failed to keep pace with the 

rate of debris proliferation.  The brief went on to look at remaining options to prevent a runaway 

reaction that would make LEO unusable over time, and lasers were identified as a hopeful 

solution.  

61 

The presenters looked at various ground, space, and airborne laser concepts that have been 

proposed over the years.  These included a ground-based high peak power LODR concept 

discussed earlier, as well as a dual use function / mission for the Air Force’s Airborne Laser 

(ABL).  Both ABL and LODR systems were multi-megawatt continuous wave and pulse laser 

designs.  The objective of LODR is to achieve surface ablation and jetting, -∆V, and early 

deorbiting.  ABL sought target destruction through thermal loading and vaporization.  Both were 

found to be suboptimal when compared to an economical 10 kW industrial solid state laser (SSL) 

combined with a modest 1 meter diameter beam director.  

Figure 69-70. 10 kW SSL from IPG Photonics (L), & 1.5 meter beam director from L3 (R). 

The presentation further observes: “Given high accuracy predictions, we may be able to use 

medium power lasers to prevent the Kessler Syndrome by nudging objects to avoid collisions – 

at much lower cost than ADR.”  The success of the lower power alternative is dependent on 

higher accuracy data.  Better data on par with the accuracy currently only available to national 

security space operators will permit future collisions to be predicted with greater accuracy.  

Longer lead times that allow repeated engagements to nudge objects out of the path of other 

objects to avoid potential collisions without the need for ADR. 

NASA has concluded that given lower probability of error and longer lead times, modest 

photonic pressure during engagements that apply approximately10 x solar constant for 20 

minutes will be sufficient.  There is no threshold intensity necessary for photonic pressure to 

work, however a favorable area-to-mass ratio is crucial to practicality.  In the end the NASA 

Ames team recommended a 10 kW laser combined with a 1.5 meter beam director, one that 

benefited from guide star corrected adaptive optics (AO).  The ideal location for such a system 

was determined to be Antarctica. 

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 Figure 71. Architecture of an AO-aided, 10kW industrial SSL. 

The space team concludes that the NASA Ames Research Center proposed laser debris nudging 

capability is the best first step in demonstrating the operational utility of SSL LODR, and FEL 

LODR, and combined LODR systems.  Modest funding would enable the integration of a 10kW 

industrial SSL with a small diameter director to study basic phenomenology of LODR.  In 

coordination with a major tracking site capable of LADAR can assist the small NASA prototype 

in acquiring and engaging a representative piece of orbital debris.  Subsequent orbital 

measurements can determine the extent to which photonic pressure influenced the debris position 

and behavior.  Concurrently, one or a few inexpensive “cubesats” equipped with SLR retro- 

reflectors and limited active telemetry can be developed and launched as piggy back payloads of 

one or more scheduled LEO missions.  This would permit a precise quantification of the effects 

of photonic pressure, in an effort to demonstrate value for collision avoidance.   

2.9.1.3.5 Proof of Effects Experimentation 

Experimentation that involves the engagement of representative debris in a vacuum chamber 

could be the first step in such an initial program.  The Thomas Jefferson Lab FEL user facility in 

Newport News, VA is ideally suited to conducting not only experiments related to the 10kW 

NASA proposal, but also the SSL LODR and FEL testing, with the FEL serving as a surrogate 

for all. In the lab, FEL sub-picosecond duration pulses can simulate the plasma jetting effects of 

the high power LODR SSL.  At the same time the FEL can with longer macro pulse 

engagements represent itself with respect to thermal loading, out-gassing, and possible 

vaporization of targeted debris.  At lower power levels and the precise desired wavelength, the 

FEL can simulate the quasi-CW power densities on target that NASA predicts with their 

industrial SSL and small beam director.  In order to achieve a representative target environment, 

a small vacuum chamber can be tailored to include a capacity to suspend the “debris coupon” 

magnetically or electrostatically to detect even miniscule accelerations one might anticipate in 

LEO.   

63 

This experimentation could be done particularly cost-effectively if included in a single 

comprehensive experimentation plan.  Our organization could plan, coordinate, execute / 

supervise, and analyze such experimentation given seed funding for that purpose.  

2.9.1.4 Space Mist 

Another promising idea that has been proposed is titled “Space Mist.”  First proposed by 

researchers at NASA’s Ames Research Center in 1990 and recently resurrected, the concept 

proposes to use frozen mist to drag an object out of orbit.  In practice, a rocket would launch a 

tank filled with liquid gas, such as carbon dioxide.  Thrusters would position the tank far ahead 

of the targeted object though directly along the calculated path that object.  Thousands of miles 

forward of the debris, the tank would spray a cloud of frozen mist. The droplets would then slow 

down and de-orbit anything they encounter such as the fast-approaching targeted object.  

According to George Sarver, the idea’s originator at Ames, a spaceship emitting a 220-pound, 

62-foot-diameter cloud of frozen mist could de-orbit dense objects such as steel nuts.  Larger 

clouds could stop less-dense items like insulation.  Once the mist dissipates, nothing remains in 

orbit along that orbital path. The tank would then fall back into the atmosphere and avoid 

becoming or causing more debris by its very presence.  , which means less clutter that could 

otherwise create more debris.  Creon Levit, the chief scientist for debris programs at Ames has 

stated that NASA could test the concept within 18 months if it were funded. 

64 

Figure 72.  NASA Ames Space Mist ODR concept proposal. 

2.9.1.5 Robots  

One type of robotic spacecraft that has been proposed is designed specifically to deorbit space 

debris with lasers.  These advanced systems could seek out debris that becomes evident when 

sunlight reflect off of it.  Alerted to the presence of the object, the “debris deorbiting” robotic 

satellite would track the debris a low power laser.  Once the debris comes within range, it would 

be engaged by a second and more powerful laser that nudges the debris out of orbit so that it 

burns up in the atmosphere.   

Another robotic concept proposes a satellite fitted with robotic arms that can grab and release 

debris, essentially tossing them earthwards, again in order to burn up in the atmosphere. Such 

spacecraft would have the capability to remove multiple pieces of debris, and advocates say that 

such a system could be tested in space within five years of receiving developmental funding. 

65 

2.9.1.6 Tether-Secured Nets 

Space tugs could have an additional function of policing up debris in their space vicinity.  These 

tugs could be equipped with conventional chemical propulsion or all electric ion engines and 

have remotely operated or fully autonomous arms equipped to grab, manipulate, and or propel 

larger pieces of space debris.  Specially-designed vehicles could intercept old rocket bodies, for 

instance, and attach a propulsion system or so-called drag augmentation device onto the object. 

The result would quicken the debris' descent to Earth. Alternatively, the tug vehicle could attach 

a drag augmentation device to several objects moving at identical velocity in close proximity, 

and perhaps a third.  Once a reasonably sized set of objects have been lassoed together the tug 

could drag them to a preferred orbit. 

As an example, the aerospace company Tethers Unlimited proposes a system called Rustler (for 

Round Up Space Trash Low Earth-orbit Remediation). Once launched into low-Earth orbit, the 

satellite releases an EDT, a 1.5-mile-long cable that conducts electricity as discussed earlier. The 

conductivity allows the tether to wrap a net around any piece of debris that it encounters, which 

it then drags into the atmosphere where the object either falls into the ocean or burns up on 

reentry. The net secures even small objects tumbling in space, a challenge for other systems.  

Tether-based solutions have been tested by NASA, including a 1996 experiment with a 12.5-mile 

cable in space.  The Rustler system has been tested on a zero-G flight and could launch on a real 

mission within five years of receiving funding. 

In the plan, two teams plan to launch a satellite carrying a long, thin metal net known as an EDT 

and attach the tether to a dead satellite (or other large space debris) using a robotic arm. Once the 

EDT becomes charged with electricity while it orbits the Earth, it will create drag that pulls the 

dead satellite down to the atmosphere where it will burn up on re-entry. 

Figure  73-74. Laser (L) and EDT (R) equipped satellites dedicated to ODR.    

66 

A giant space debris net several kilometers in size has been proposed as a collaboration between 

Japan Aerospace Exploration Agency (JAXA) and Nitto Seimo Co, a 100-year-old Japanese 

maker of fishing nets in an effort to collect debris from orbital space.  Nitto Seimo is a 100-year 

old fishing net maker notable for inventing the world's first machine to make durable knotless 

fishing nets in 1925 and capturing half of the fishing net market in Japan. It hopes its expertise in 

catching fish will translate to catching space debris.  

The Japanese plan will see a satellite attached to a thin metal net spanning several kilometers 

launched into space. The net is then detached, and begins to orbit earth, sweeping up space waste 

in its path and then pulling them down to Earth.  After catching the debris for several weeks, the 

scientists back down on Earth will activate the electrical charge of the net which will have the 

net move  towards Earth due to the planet’s magnetic fields attraction of  the electrified net.  

Both  the net and its catch will then burn up in the atmosphere.  It is likely the nets will target the 

orbital paths of space shuttles which are constantly monitored for debris. By remaining in orbit 

collecting rubbish for several weeks the trip will become financially worthwhile, before sending 

another net into space.   

Inspired by a basic fishing net concept, the super-strong space nets have been the subject of 

extensive research by Nitto Seimo for the past six years and consist of three layered metal 

threads, each measuring 1mm diameter and intertwined with fibres as thin as human hair.  Nitto 

Seimo started development of the net in 2005 and has created a usable tether material composed 

of three layers of metal threads, each  layer measuring 1 millimeter in diameter, combined with 

very thin fibers. 

  Figures 75-76.  JAXA (L), teamrd with Nitto Seimo Co. co-developed debris capturing net (R). 

2.9.1.7 Solar Sails 

The sun’s radiation can be harnessed to exert photon-induced force on solar sails composed of  

ultra-thin fabric material that is cheap and portable.  The photonic pressure of solar light acts on 

the solar sail much like wind propels a sailboat.  These sails can clean up orbit by slowing debris 

enough that it de-orbits. For example, an expandable 97-square-foot sail can be launched as a 

secondary payload on even a small 110-pound satellite, and an onboard system or ground control 

triggers its deployment. Conductive coils embbeded in the sail control its angle of incidence to 

67 

the sun so that it can maneuver a satellite so as to force it to deorbit.  The sail and the satellite 

would disintegrate together in the atmosphere.  Solar sail technology is mature and has existed 

for decades.  This includes sail-equipped spacecraft in the mid-1970s that was intended to ride 

along with Halley’s Comet; however the spacecraft was never launched.   Another example 

involves the large solar arrays that are currently affixed to the Messenger spacecraft, which are 

helping steer the spacecraft to the planet Mercury. Most recently, JAXA launched a solar-sail- 

propelled “space yacht” called Ikaros. But the solar sails precisely controllable enough to remove 

debris are still years away.  

2.9.1.8 Orbital Spheres 

Adhesive Synthetic Trash Recovery Orbital Spheres, or “ASTROS” are essentially large sticky 

balls/shells or “space flypaper.” The balls consist of a layer of metallic foam (such as silicon 

carbide) and an outer shell of adhesive (such as aerogels or resins). They attach themselves to 

debris and once a mass of debris has been collected, then deorbit into the atmosphere where both 

are incinerated.  The large shells would spanning a mile (1.6 km) in diameter.  As small particles 

pass through the foam-like contents of the internal volume of the ball they would lose energy.  

Those that pass through would lose velocity and reenter the Earth’s atmosphere more rapidly.  

The debris that does not pass through the ball completely would likely adhere to it internally or 

externally.  Since the ball itself would lose velocity over time due to its lightweight relative to its 

large LEO cross-section, and the countless energy-depleting impacts with counter-orbiting 

debris, it too would reenter the atmosphere fairly quickly, dragging with it captured debris that it 

had not already deorbited.   Another version of this is a similarly sized “NERF Ball” that would 

deflect debris entirely thereby absorbing their energy, slow their velocities, thereby lowering 

their perigees to increase atmospheric drag for quick reentry. 

    Figures 77-78.  Solar sail propulsion for ODR (L), and  adhesive shells dragging debris (R).   

68 

2.10 Potential Orbital Debris Removal X-Prize 

The X Prize Foundation addresses the world’s Grand Challenges by creating and managing 

large-scale, high-profile, incentivized prize competitions that stimulate investment in research 

and development worth far more than the prize itself.  It motivates and inspires brilliant 

innovators from all disciplines to leverage their intellectual and financial capital. On the X Prize 

Foundation website at http://xprize.org/about/who-we-are under “concepts under consideration,” 

“Orbital Debris Removal” is discussed as a potential candidate prize:    

Millions of pieces of debris are currently orbiting Earth at altitudes that pose a danger to 

satellites and human spacecraft. The threat from such debris is predicted to rise 50% in 

the coming decade and quadruple in the next 50 years. Large object collisions are 

particularly dangerous, due to the ensuing creation of additional debris. Teams competing 

in the Orbital Debris competition must select a target piece of orbital debris and either de- 

orbit the debris or move the debris in a predicted and accurate fashion to a new orbit 

deemed non-threatening by a panel of expert judges. The first team to complete this task 

will be determined the winner. 

The Space Team believes that if the urgency of the space debris can be communicated to a large 

public and private audience in the near term, that the X Prize Foundation will make a decision to 

activate the Orbital Space Debris prize by announcing and funding it.  

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Chapter 3: 

The Proposed Sustainable Organization 

3.1 The Space Team concludes that in the near term organization dedicated to removing debris 

from Earth orbit in order to preserve the viability of orbital space is sustainable.  Our 

organization’s expertise centers on research, technology analysis, project management, and 

government-industry coordination. The team constitutes a first iteration with the potential to 

evolve later. 

3.2 The team believes that space systems insurers and operators will identify a value in lowering 

the risks of debris collisions with the systems they operate and insure and pay for our services in 

helping to get it done.  Insurers and operators will pay for our research, down-selection analysis, 

project management, and coordination services in support of ODR technology development and 

demonstration.   

3.3 The team also believes that cash rich non-space faring nations will identify a value in 

increased influence over space related high technology development and playing a larger role in 

the future of space.  Nations such as the UAE, Saudi Arabia, and Brazil might therefore pay for 

our organization’s services in facilitating their full inclusion in United Nations space bodies such 

as the IADC.  The team likewise believes those same wealthy nations will fund industry to 

support the development and demonstration of ODR capabilities, as a global contribution that 

garners high technology access and national prestige.   

3.4 The space team concludes that the NASA Ames Research Center proposed laser debris 

nudging capability is the best first step in demonstrating the operational utility of SSL LODR, 

and FEL LODR, and combined LODR systems.  Modest funding would enable the integration of 

a 10kW industrial SSL with a small diameter director to study basic phenomenology of LODR.  

In coordination with a major tracking site capable of LIDAR and SLR, such as MSSS (AMOS) 

or ESA SLR, NASA Ames can prototype acquisition and engagement of orbital debris.  

Concurrently, one or a few inexpensive “cubesats” equipped with SLR retro-reflectors and 

specialized active telemetry developed at Ames can be launched as piggy back payloads on one 

or more scheduled LEO missions so that the precise quantification of the effects of photonic 

pressure and be observed in an effort to demonstrate value for collision avoidance.   

3.5 Experimentation that involves the engagement of representative debris in a vacuum chamber 

could be the first step in such an initial program.  The Thomas Jefferson Lab FEL user facility in 

Newport News, VA is ideally suited to conducting not only experiments related to the 10kW 

NASA proposal, but also the higher power SSL LODR and FEL testing, with the FEL serving as 

a surrogate for all.  In order to achieve a representative target environment, a small vacuum 

chamber can be tailored to include a capacity to suspend the “debris coupon” magnetically or 

electrostatically to detect even miniscule accelerations one might anticipate in LEO.   This 

experimentation could be done particularly cost-effectively if included in a single comprehensive 

experimentation plan.  Our organization could plan, coordinate, execute / supervise, and analyze 

experimentation given seed funding as a first funded task.  

70 

Bibliography 

References 

[a]  85.03.00   Joseph A. Carroll- Guidebook for Analysis of Tether Applications  

[b]  92.01.16   Claude Phipps - Workshop Report - Astrodynamics of Interception  

[c]  93.00.00   Joseph A. Carroll - SEDS Deployer Design and Flight Performance  

[d]  93.00.00   Claude Phipps - Laser Impulse Space Propulsion (LISP) 

[e]  95.00.00   Orbital Debris - A Technical Assessment NRC 

[f]  95.00.00   Joseph A. Carroll - Tether Transport Facility 

[g]  95.00.00   Joseph A. Carroll - Tethers for Small Satellite Applications 

[h]  95.00.00   Claude Phipps - Laser Role in Planetary Defense 

[i]  95.05.26   Claude Phipps - Laser Role in Planetary Defense 

[j]  95.11.00   Interagency Report on OSD 

[k]  96.12.06   Claude Phipps - Laser Deflection of Near-Earth Objects 

[l]  99.00.00   UN Technical Report on Space Debris 

[m]  99.00.00   Technical Report on Orbital Debris - UN  

[n]  01.02.10   Claude Phipps - Optimum Parameters for Laser-Launching Objects  

[o]  02.10.24   Space Transport Development Using Orbital Debris  

[p]  02.12.02   Space Transport Development Using Orbital Debris  

[q]  03.07.20   Joseph A. Carroll - EDDE Overview Paper 

[r]  03.07.23   Joseph A. Carroll - EDDE Overview Presentation 

[s]  04.10.00   George Neil - Airborne Megawatt FEL DEPS 2004 

[t]  04.10.00   Claude Phipps - Would You Let Your Kids Ride a Laser Beam  

[u]  05.07.13   Schafer Corporation - SUSTAIN Brief (Archive) 

[v]  05.10.00   George Neil - Airborne Megawatt FEL DEPS 2005  

[w]  06.11.01   George Neil - Airborne Tactical FEL DEPS 2006 - Paper  

[x]  06.11.01   George Neil - Airborne Tactical FEL DEPS 2006 - Presentation  

[y]  07.00.00   SSP-07 TP Report on Space Traffic Management 

[z]  08.04.00   Lucy Rogers - It's ONLY Rocket Science  

[aa]  09.00.00   George Neil - MW Airborne FEL  

[bb]  09.02.23   Brian Weeden - Billiards in Space  

[cc]  09.03.08   Donald J. Kessler - The Kessler Syndrom  

[dd]  09.07.13   Brian Weeden - The Numbers Game  

[ee]  09.12.00   Roy Whitney - FEL Orbital Debris Removal  

[ff]  09.12.08   NASA, DARPA, Space Junk  

[gg]  09.12.08   ODR Conference Agenda  

[hh]  10.00.00   RAND Corporation Space Debris 

[ii]  10.02.11   Joseph A. Carroll - Star EDDE Presentation  

[jj]  10.02.11   Creon Levit & Will Marshall Improved Orbit Predictions Using TLEs  

[kk]  10.05.19   Joseph A. Carroll - EDDE  

[ll]  10.05.19   Space Debris and the Cost of Space Operations  

[mm]  10.06.28   National Space Policy  

[nn]  10.07.23   Evisat Poses Debris Threat  

[oo]  10.08.11   Brian Weeden - Saving Earth Orbit  

71 

[pp]  10.09.00   Economist - Space Debris  

[qq]  10.10.00   Endangered Birds - ASAT Danger  

[rr]  10.10.19   Bin Song -Tether Net Gripper  

[ss]  10.10.19   Claudio Bombardelli - Electrodynamic Tethers  

[tt]  11.02.00   Overview of Legal and Policy Challenges to ODR  

[uu]  11.02.09   AIAA Hattis - Orbital Debris - Human Spaceflight - Space Technology  

[vv]  11.03.10   Mason, Stupl, Marshall, Levit - Orbital Debris-Debris Collision Avoidance 

[ww]  11.03.18   Space Debris Panel - Combined  

[xx]  11.07.24   Orbital Debris-Debris Collision Avoidance  

[yy]  11.07.26   Directed Energy – Orbital Debris Removal 

[zz]  11.07.26   Orbital Debris - DARPA  

[aaa]  11.07.27   Electromagnetic Tethers - Wiki  

[bbb]  11.07.27   Haystack Radar  

[ccc] 11.07.27   MOSS SSN  

[ddd] 11.07.28   Lockheed Martin Co HAA  

[eee]  11.08.10   Henze, Marshall, Mason, Stupl, Levit - Ames Space Debris Research  

[fff]  11.10.00   Space as a Sustainable Commons  

Figures 

Figure 1.   http://www.popsci.com/technology/article/2010-02/ 

Figure 2.   Henze, Marshall, Mason, Stupl, Levit - Ames Space Debris Research 

Figure 3.   Henze, Marshall, Mason, Stupl, Levit - Ames Space Debris Research 

Figure 4.   http://www.astronautix.com/craft/usa.htm 

Figure 5.   http://www.destination-orbite.net/lanceurs/surveillance.php 

Figure 6.   http://www.tu-braunschweig.de/presse/medien/ 

Figure 7.   http://ecolocalizer.com/2009/08/14/4-million-pounds-of-junk-polluting-orbit/ 

Figure 8.   http://www.newscientist.com/blog/space/2007_03_01_archive.html 

Figure 9.   http://www.ufocasebook.com/bestufopictures5.html 

Figure 10.  http://hipstersgonnahip.blogspot.com/2011/02/earth-to-be-space-station-we.html 

Figure 11.  http://www.disclose.tv/forum/nasa-sts-88-black-debris-or-something-else  

Figure 12.  http://www.weirdwarp.com/2009/11/space-junk-needs-cleaning-up-wheres-the-bin/ 

Figure 13.  http://www.gotgeoint.com/archives/space-junk-starting-to-reach-mother-earth/ 

Figure 14.  http://www.popsci.com/technology/article/2010-10/debris-rains-on-chinese-villages 

Figure 15.  http://shadowedhistory.com/ 

Figure 16.  Star Technology and Research, Inc. 

Figure 17.  Henze, Marshall, Mason, Stupl, Levit - Ames Space Debris Research 

Figure 18.  http://www.spacebridges.com/S3-blog-English/bid/69274/S3-infos-Space-debris 

Figure 19.  http://www.spaceweather.com/glossary/collidingsatellites.htm  

Figure 20.  http://go2add.com/meteorites/abee.php 

Figure 21.  http://www.arizonaskiesmeteorites.com/AZ_Skies_Links/Campos_For_Sale/ 

Figure 22.  http://en.wikipedia.org/wiki/Spacecraft_cemetery 

Figure 23.  http://www.daviddarling.info/encyclopedia/G/graveyard_orbit.html 

Figure 24.  Creon Levit and Space Team – Errors Over Time  

Figure 25.  Creon Levit and Space Team – Errors in Probability  

72 

Figure 26.  http://www.au.af.mil/au/awc/awcgate/usspc-fs/space.htm 

Figure 27.  http://www.panoramio.com/photo/18524004 

Figure 28.  http://www.globalsecurity.org/space/systems/amos.htm 

Figure 29.  http://www.spacedaily.com/news/spysat-00d.html 

Figure 30.  http://space.skyrocket.de/doc_sdat/sbss-1.htm 

Figure 31.  http://www.ballaerospace.com/page.jsp?page=189 

Figure 32.  http://www.boeing.com/defense-space/space/satellite/sbss.html 

Figure 33.  http://www.wpafb.af.mil/library/factsheets/factsheet.asp?id=9454 

Figure 34.  http://www.boeing.com/Features/2010/11/bds_maui_11_15_10.html 

Figure 35.  http://en.wikipedia.org/wiki/File:Starfire_Optical_Range.jpg  

Figure 36.  http://en.wikipedia.org/wiki/File:Starfire_Optical_Range.jpg 

Figure 37.  http://www.nature.com/news/2011/110422/full/news.2011.254.html 

Figure 38.  http://www.facebook.com/DARPA?sk=wall&filter=2 

Figure 39.  http://www.alphabetics.info/international/2009/07/22/july-22/ 

Figure 40.  http://www.lockheedmartin.com/products/SBandAdvancedRadar/index.html 

Figure 41.  http://www.ausairpower.net/APA-Sov-FOBS-Program.html 

Figure 42.  http://weapons.technology.youngester.com/2010/05/active-phased-array-radar.html 

Figure 43.  http://www.flickr.com/photos/52471863@N02/5558389790/ 

Figure 44.  http://www.wpafb.af.mil/news/story.asp?id=123101570 

Figure 45.  http://orbitaldebris.jsc.nasa.gov/measure/radar.html 

Figure 46.  http://bbs.keyhole.com/ubb/ubbthreads.php?ubb=showflat&Number=1199279 

Figure 47.  http://www.boeing.com/defense-space/space/gmd/gallery/sbx001.html 

Figure 48.  http://en.wikipedia.org/wiki/Space-Based_Infrared_System 

Figure 49.  http://www.lockheedmartin.com/products/SpaceBasedInfraredSystemHigh/ 

Figure 50.  http://geimint.blogspot.com/2008/06/soviet-russian-space-surveillance.html 

Figure 51.  http://mt-milcom.blogspot.com/2008/02/russian-space-surveillance-sourcebook.html 

Figure 52.  http://geimint.blogspot.com/2008/06/soviet-russian-space-surveillance.html 

Figure 53.  http://geimint.blogspot.com/2008/06/soviet-russian-space-surveillance.html 

Figure 54.  http://www.thelivingmoon.com/45jack_files/03files/GRAVES.html 

Figure 55.  http://www.thelivingmoon.com/45jack_files/03files/GRAVES.html 

Figure 56.  http://www.thelivingmoon.com/45jack_files/03files/GRAVES.html 

Figure 57.  http://lfvn.astronomer.ru/report/0000048/004/index.htm 

Figure 58.  http://www.qwiki.com/q/?_escaped_fragment_=/Satellite_laser_ranging 

Figure 59.  http://en.wikipedia.org/wiki/File:Fig12_Tether_System.PNG 

Figure 60.  http://en.wikipedia.org/wiki/Space_tether 

Figure 61.  Star Inc. presentation 

Figure 62.  http://www.popsci.com/node/22487 

Figure 63.  Claude Phipps - Laser Role in Planetary Defense 

Figure 64.  Space Team Short Pulse (internet image background no reference available) 

Figure 65.  http://www.ar15.com/forums/t_1_5/1152415_.html 

Figure 66.  http://www.4gls.ac.uk/ERLP.htm 

Figure 67.  http://www.lanl.gov/science/1663/june2010/story4b.shtml 

Figure 68.  http://www.geekwithlaptop.com/tag/nasa-laser-debris 

Figure 69.  Henze, Marshall, Mason, Stupl, Levit - Ames Space Debris Research 

Figure 70.  Henze, Marshall, Mason, Stupl, Levit - Ames Space Debris Research 

73 

Figure 71.  Henze, Marshall, Mason, Stupl, Levit - Ames Space Debris Research 

Figure 72.  http://www.popsci.com/technology/article/2010-07/cluttered-space 

Figure 73.  http://www.popsci.com/technology/article/2010-07/cluttered-space 

Figure 74.  http://www.popsci.com/technology/article/2010-07/cluttered-space 

Figure 75.  http://space.azzopardi.info/ 

Figure 76.  http://www.yahind.com/fishing-net-to-collect-debris-from-space_18104.html 

Figure 77.  http://www.popsci.com/technology/article/2010-07/cluttered-space 

Figure 78.  http://www.popsci.com/technology/article/2010-07/cluttered-space 

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