Space debris was first recognized as a serious problem in the late 1970s and early 1980s.² However, several events in recent years have significantly increased the amount of debris in orbit. In 2007, the Chinese government used a dead Chinese weather satellite, Fengyun-1C, as a target for the test of an antisatellite missile system. As of 2011, 3,135 pieces of debris from the Fengyun-1C satellite have been catalogued in LEO, and NASA’s Orbital Debris Program Office estimates that more than 150,000 pieces of debris larger than one centimeter in diameter were generated by this impact.³ In 2009, a satellite operated by Iridium Communications, Inc., was destroyed in a collision with a defunct Russian military satellite, the first major collision between an operational satellite and space debris. The Iridium collision generated about 1,000 pieces of debris larger than 10 centimeters, and many more smaller pieces.⁴ Experts fear that if the amount of debris in orbit reaches a critical mass, a few major debris-creating episodes (whether intentional or accidental) could set off a sequence of ever more frequent collisions—a kind of chain reaction that would expand until, within decades, certain regions of Earth orbit would be rendered virtually unusable. This “collisional cascading” is known as the Kessler Syndrome, named after NASA scientist Donald Kessler, who first proposed this possibility in 1978.⁵ Some studies indicate that Earth orbit is already unstable at certain altitudes, in the sense that absent debris mitigation efforts, a collisional cascade could already be inevitable.⁶

Efforts to address the space debris problem fall into three categories: (1) debris tracking, (2) growth mitigation, and (3) removal.

Tracking

In order for operational spacecraft to avoid space debris, their operators must have comprehensive knowledge of the population of space objects, particularly of any objects that might cross their orbital paths. Knowledge of the space environment is referred to as space situational awareness (SSA). SSA is obtained through space surveillance, which is the detection, correlation, characterization, and orbit determination of space objects. The US Department of Defense’s Space Surveillance Network (SSN) maintains the “world’s most capable space surveillance network, consisting of ground-based radars, optical telescopes, and satellites.”⁷ The SSN is capable of tracking objects as small as five centimeters in diameter in low Earth orbit and about one meter in diameter in geosynchronous orbit.⁸ The United States makes much of this data publicly available through the SSA Sharing Program, which is administered by the US Strategic Command and is available at http://www.space-track.org.

In addition to the SSA Sharing Program, several non-US government organizations also provide SSA tracking data. The European Space Agency is developing its own SAA capability under the European SSA Preparatory Programme.⁹ In 2009, the three largest commercial satellite companies, Intelsat, Inmarsat, and SES, formed the non-profit Space Data Association (http://www.space-data.org/sda) to share SSA data. The Center for Space Standards and Innovation (CSSI) also provides SSA services. CSSI operates the satellite tracking website, CelesTrak (http://celestrak.com), which redistributes two-line element sets and information from the space-track.org website, supplemented with its own data and analysis. CSSI also offers a service called Satellite Orbital Conjunction Reports Assessing Threatening Encounters in Space (SOCRATES) (http://celestrak.com/SOCRATES). SOCRATES provides information on pending orbital conjunctions during the coming week. Finally, the International Scientific Optical Network (ISON) (http://www.isonteam.com) describes itself as a “scientific project” initiated by the Keldysh Institute of Applied Mathematics of the Russian Academy of Sciences in 2001. ISON receives its data from 25 optical telescopes located at 18 observation facilities.¹⁰

Mitigation

Debris mitigation efforts first began in the early 1980s. One early solution implemented by McDonnell Douglas, for example, was to modify its Delta booster so that it did not explode in orbit after completing its mission.¹¹ In 1995, NASA became the first space agency to issue comprehensive orbital debris mitigation guidelines.¹² Two years later, an interagency working group led by NASA and the Department of Defense developed Orbital Debris Mitigation Standard Practices for all US government satellites and launch vehicles. Other countries and organizations, including Japan, France, Russia, and the European Space Agency (ESA), have followed suit with their own orbital debris mitigation guidelines.

In 2002, the Inter-Agency Space Debris Coordination Committee (IADC), which is comprised of the space agencies of 11 countries and ESA, adopted a set of guidelines designed to mitigate the growth of the orbital debris population. In 2007, after a multiyear effort, the United Nations’ Committee on the Peaceful Uses of Outer Space (COPUOS) developed and adopted a consensus set of space debris mitigation guidelines similar to the IADC guidelines, which were subsequently endorsed by the full U.N. General Assembly.¹³ The COPUOS guidelines include seven recommendations:

1. Limit debris released during normal operations.
2. Minimize the potential for break-ups during operational phases.
3. Limit the probability of accidental collision in orbit.
4. Avoid intentional destruction and other harmful activities.
5. Minimize potential for postmission break-ups resulting from stored energy.
6. Limit the long-term presence of spacecraft and launch vehicle orbital stages in low-Earth orbit region after the end of their mission.
7. Limit the long-term interference of spacecraft and launch vehicle orbital stages with the geosynchronous Earth orbit region after the end of their mission.14

In addition to the COPUOS and national orbital debris mitigation guidelines, there have been several efforts to develop more comprehensive “rules of the road” for outer space operations. In December 2008, the European Union proposed a draft Code of Conduct for Outer Space Activities, which would require, among other things, that participating States “refrain from intentional destruction of any on-orbit space object or other harmful activities which may generate long-lived space debris,” and “adopt, in accordance with their national legislative process, the appropriate policies and procedures in order to implement” the COPUOS debris mitigation guidelines.¹⁵ Although initially responding favorably to this effort, the United States announced in January 2012 that it would not support the European Code of Conduct because the US government found it to be “too restrictive.”¹⁶ Instead, US Secretary of State Hillary Rodham Clinton announced that the United States would “join with the European Union and other nations to develop an International Code of Conduct for Outer Space Activities” that “will help maintain the long-term sustainability, safety, stability, and security of space by establishing guidelines for the responsible use of space” and “reverse the troubling trends that are damaging our space environment.”¹⁷

Removal

There are generally two forms of debris removal: self-removal and external removal. Self-removal is where, at the end of its useful life, a spacecraft either removes itself from orbit by entering into a decaying orbit that will reenter the atmosphere in a reasonable timeframe (the U.S. Standard Practices require that this be done within 25 years of the end of the satellite’s mission), or moves itself into a graveyard orbit out of the way of other spacecraft. Technologies are currently being developed as alternatives to using valuable propellant to deorbit spacecraft, such as electrodynamic tethers and sail-like attachments that would be installed on a spacecraft prior to launch and, when deployed at the end of the spacecraft’s useful life, would create drag that would eventually deorbit the spacecraft.¹⁸

Spacecraft in high-Earth orbits cannot realistically carry enough extra propellant to move into atmosphere dispersal orbits at the end of their missions. The International Telecommunications Union therefore requires that States ensure that geostationary satellites are transferred to a “supersynchronous graveyard orbit” that does not intersect with the geosynchronous orbit (GSO) at the end of their useful life.¹⁹ In the United States, this requirement has been implemented in Section 25.283(a) of the Federal Communication Commission’s rules for satellite operations, which provides that “a space station authorized to operate in the geostationary satellite orbit under this part shall be relocated, at the end of its useful life, barring catastrophic failure of satellite components, to an orbit with a perigee with an altitude of no less than: 36,021 km [22,382 miles].”²⁰ Unfortunately, spacecraft operators do not always comply with this requirement. In 2009, for example, only 11 of 21 satellites in GSO that reached their end of life were disposed of in proper graveyard orbits.²¹

While self-removal is the preferred mechanism for removing debris from orbit, this is not possible for the thousands of pieces of debris currently in orbit without any built-in means of self-removal. Proposed mechanisms for external removal of debris from orbit include, for example, building spacecraft to rendezvous with and capture debris and ground-based “laser brooms” to sweep debris from orbit.

There are two problems with currently proposed external removal mechanisms. First, none of the proposed mechanisms are economically feasible with today’s technology. Second, since the Outer Space Treaty provides that launching States retain ownership, jurisdiction, and control of their space objects and there is no law of salvage for outer space similar to the law of salvage under maritime law, one State cannot remove another State’s nonfunctionary spacecraft from orbit without permission. States would likely be willing to consent to the removal of their debris in most cases, but obtaining consent for each item of debris would be time-consuming and inefficient, the origin of many items of debris cannot be determined with certainty, and States would be less willing to allow another State to interact with debris that may contain national security secrets, such as derelict reconnaissance satellites. Accordingly, many technological solutions to the space debris problem would need to be accompanied by an international legal framework authorizing the removal efforts. u

Endnotes

1. National Aeronautics and Space Administration, Frequently Asked Questions: Orbital Debris, http://www.nasa.gov/news/debris_faq.html.

2. Jim Schefter, The Growing Peril of Space Debris, Popular Science (July 1982).

3. CelesTrak.com, Chinese ASAT Test (updated May 20, 2011), http://celestrak.com/events/asat.asp; National Aeronautics and Space Administration, Fengyun-1C Debris: One Year Later, 12 Orbital Debris Q. News 1, 3 (2008), available at http://www.orbitaldebris.jsc.nasa.gov/newsletter/pdfs/ODQNv12i1.pdf.

4. Veronika Oleksyn, What a Mess! Experts Ponder Space Junk Problem, USA Today, Feb. 19, 2009, available at http://www.usatoday.com/tech/science/space/2009-02-19-space-junk_N.htm; Philip Hattis, The Growing Menace of Orbital Debris, Livebetter eMagazine, Jan. 2012, http://www.centerforabetterlife.com/eng/magazine/article_detail.lasso?id=265.

5. Donald J. Kessler & Burton G. Cour-Palais, Collision Frequency of Artificial Satellites: The Creation of a Debris Belt, 83 J. of Geophysical Res. 2637–46 (1978).

6. Donald J. Kessler et al., The Kessler Syndrome: Implications to Future Space Operations, 33rd Annual AAS Guidance and Control Conference, Paper AAS 10-016 (Feb. 2010), available at http://webpages.charter.net/dkessler/files/Kessler%20 Syndrome-AAS%20Paper.pdf; Donald J. Kessler & Phillip D. Anz-Meador, Critical Number of Spacecraft in Low Earth Orbit: Using Fragmentation Data to Evaluate the Stability of the Orbital Debris Environment, Third European Conference on Space Debris (Mar. 2001), available at http://webpages.charter.net/dkessler/files/CriticalNumberofSpacecraftinLow.pdf.

7. James D. Randleman & Robert E. Ryals, Spacecraft Operator Duty of Care, AIAA Space 2011 Conference & Exposition 3 (2011).

8. National Aeronautics and Space Administration, Space Debris and Human Spacecraft, http://www.nasa.gov/mission_pages/station/news/orbital_debris.html.

9. European Space Agency, Space Situational Awareness, http://www.esa.int/esaMI/SSA.

10. Tiffany Chow, Space Situational Awareness Sharing Program: An SWF Issue Brief, The Secure World Foundation (Sept. 22, 2011), http://swfound.org/media/3584/ssa_sharing_program_issue_brief_nov2011.pdf.

11. Jim Schefter, The Growing Peril of Space Debris, Popular Science (July 1982).

12. NASA Orbital Debris Program Office, Orbital Debris Mitigation, http://orbitaldebris.jsc.nasa.gov/mitigate/mitigation.html.

13. G.A. Res. 62/217, International Cooperation in the Peaceful Uses of Outer Space, U.N. GAOR, 62nd Sess. U.N. Doc. A/RES/62/217, at ¶26 (Dec. 22, 2007).

14. United National Office for Outer Space Affairs, Space Debris Mitigation Guidelines of the Committee on the Peaceful Uses of Outer Space, Official Records of the General Assembly, 62nd Sess., Supp. No. 20 (A/62/20), paras. 117 and 118 and annex., available at http://orbitaldebris.jsc.nasa. gov/library/Space%20Debris%20Mitigation%20Guidelines_COPUOS.pdf.

15. Council of the European Union, Draft Code of Conduct for Outer Space Activities, at art. II, § 5 (2008), available at http://www.eu2008.fr/webdav/site/PFUE/shared/import/1209_CAGRE_ resultats/Code%20of%20Conduct%20for%20outer%20space%20activities_EN.pdf.

16. Marcus Weisberger, U.S. Won’t Accept EU Code of Conduct for Space, Space News, Jan. 12, 2012 (quoting U.S. Undersecretary of State for Arms Control and International Security Ellen Tauscher), http://www.spacenews.com/policy/120112-wont-adopt-code-conduct-space.html.

17. Press Release, U.S. Secretary of State Hillary Rodham Clinton, International Code of Conduct for Outer Space Activities (Jan. 17, 2012), http://www.state.gov/secretary/rm/2012/01/180969.htm.

18. See, e.g., Bill Christensen, The Terminator Tether Aims to Clean Up Low Earth Orbit, Space.com, Nov. 17, 2004, http://www.space.com/537-terminator-tether-aims-clean-earth-orbit.html (tethers); Jonathan Amos, How Satellites Could “Sail” Home, BBC News.com, May 3, 2009, http://news.bbc.co.uk/2/hi/science/nature/8029899.stm (sails).

19. Francis Lyall & Paul B. Larsen, Space Law: A Treatise 246 (Ashgate, 2009) (citing International Telecommunications Union Radiocommunication Sector Recommendation S.1003-1 (01/04), “Environmental Protection of the Geostationary Orbit”).

20. 47 C.F.R. § 25.283(a).

21. European Space Agency, Classification of Geosynchronous Objects (Feb. 2010), at 126, available at http://lfvn.astronomer.ru/files/COGO-issue12.pdf.