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National Aeronautics and Space Administration Orbital Debris Quarterly News Volume 10, Issue 2 April 2006 Instability of the Current Orbital Debris Population A paper addressing the inevitable growth of fi delity debris evolutionary model with an updated Inside... future debris populations was published by Sci- debris population as initial conditions, the new study Draft UN Space ence in its 20 January 2006 issue. The paper, writ- published in Science also made a key assumption - it ten by J.-C. Liou and N. L. Johnson, summarized assumed no new launches were conducted after 1 Debris Mitigation the results of recent research by the NASA Orbital January 2005. This assumption eliminated several Guidelines ..................2 Debris Program Offi ce. Currently more than 9000 major uncertainties in future projection simulations, objects, with a combined mass exceeding 5 million including future launch frequency, types of satellites Disposal of kilograms, are tracked by the U.S. Space Surveillance launched, and their physical and orbital specifi ca- Geosynchronous Network and maintained in the U.S. satellite catalog. tions. Although “no new future launches” is unre- Spacecraft in 2005 .....2 Several environment projection studies conducted alistic, it does provide a bottom line assessment of between 1991 and 2001 indicate that with various the current debris environment. In other words, the Flux Comparisons assumed future launch rates, the debris populations results represent the best-case scenario. from the Goldstone, at some altitudes in low Earth orbit (LEO) will be- The simulated 10 cm and larger LEO popula- Haystack, and come unstable. Collisions will take over as the domi- tion indicates that collision fragments replace other HAX Radars ...............2 nant debris generation mechanism, and the debris decaying debris (due to atmospheric drag) through generated will feed back to the environment and 2055, keeping the total LEO populations approxi- Modeling the Effect induce more collisions. mately constant. Beyond 2055, however, new col- of High Solar Activity In addition to using a recently developed high continued on page 2 on the Orbital 12000 Debris Environment ..4 Total Orbital Debris Intacts + mission related debris Photometric Study .....5 10000 Explosion fragments Collision fragments Developing a Mass Density Distribution 8000 for Breakup Debris ....7 6000 4000 2000 Effective Number of Objects (>10cm, LEO) 0 1950 1970 1990 2010 2030 2050 2070 2090 2110 2130 2150 2170 2190 2210 A publication of Year The NASA Orbital Effective number of LEO objects, 10 cm and larger, from the simulation. The effective number is defi ned as the fractional time, Debris Program Offi ce per orbital period, an object spends between 200 and 2000 km altitudes. The future projection parts of the curves (years 2005 to 2204) are averages from 50 Monte Carlo runs. Intacts are rocket bodies and spacecraft that have not experienced breakups. Orbital Debris Quarterly News Debris Population continued from page 1 and 1000 km altitudes. Even without any new as satellites continue to be launched into space. lision fragments outnumber decaying debris, launches, this region is highly unstable. Debris The paper concludes that to better limit the and force the total population to increase. De- populations in this “red zone” will approxi- growth of future debris populations, active re- tailed analysis shows that the predicted future mately triple in the next 200 years, leading to a moval of objects from space needs to be con- catastrophic collisions and the resulting popu- factor of 10 increase in collision probability. sidered. ♦ lation increase are non-uniform throughout In reality, the future debris environment LEO. The most active region is between 900 is likely to be worse than the study suggested, Draft United Nations Space Debris Mitigation Guidelines The Scientifi c and Technical Subcommittee tailed Space Debris Mitigation Guidelines of to review the document carefully during 2006 (STSC) of the United Nations Committee on the Inter-Agency Space Debris Coordination with the objective of adopting the guidelines in the Peaceful Uses of Outer Space (COPUOS) Committee (IADC). After meetings in Vienna their current or revised form at the 44th meeting held its annual meeting at the UN complex in in February and June of 2005, the Space Debris of the Subcommittee in February 2007. Vienna, Austria, during 20 February – 3 March Working Group met again on 23 February 2006 During this session of the STSC, a special 2006. Since 1994 space debris has been a topic and completed its primary task on 1 March, workshop on nuclear power sources in space was on the Subcommittee’s agenda, and the fi rst when it offi cially presented the Subcommittee held under the joint sponsorship of COPUOS work plan culminated with the 1999 publication with the draft document entitled UN COPUOS and the International Atomic Energy Agency of Technical Report on Space Debris. STSC Space Debris Mitigation Guidelines. (IAEA). A presentation prepared by the STSC The current work plan for the years 2005- The concise document contains seven Space Debris Working Group on special space 2007 calls upon a special Space Debris Work- numbered guidelines addressing debris released debris issues associated with space nuclear pow- ing Group to prepare for the Subcommittee a intentionally or unintentionally during deploy- er sources was delivered. ♦ space debris mitigation document with high- ment, operations, and post-disposal in all altitude level guidelines consistent with the more de- regimes. STSC Member States were requested Disposal of Geosynchronous Spacecraft in 2005 One of oldest space debris mitigation perturbations for a very long time. orbits, and 17 (85%) reached orbits at least 200 guidelines addresses the disposal of spacecraft The purpose of maneuvering spacecraft km above GEO. operating in the geosynchronous (GEO) re- out of the GEO region is to prevent their possi- All seven U.S. spacecraft (four govern- gime. Today, the space debris mitigation guide- ble future collision with operational spacecraft. ment-owned and three commercial) which were lines of all major space-faring nations and the Not only could the operational spacecraft be se- moved into disposal orbits achieved the objec- Inter-Agency Space Debris Coordination Com- verely damaged in such a collision, but also new tive of non-interference with GEO for at least mittee (IADC), as well as a recommendation of orbital debris could be created, which, in turn, 100 years. In fact, the oldest GEO spacecraft to the International Telecommunication Union, could pose a threat to other spacecraft. be retired in 2005 belonged to the U.S., was 21 call for transferring GEO spacecraft at the end A total of 22 GEO spacecraft, a larger years old, and was able to reach one of the high- of their mission into disposal orbits above the number than usual, terminated their missions est disposal orbits of the year, with its lowest GEO region, which is normally defi ned as the during 2005. Unfortunately, two of these point more than 400 km above GEO. region within 200 km of the geosynchronous spacecraft, INTELSAT 804 and UFO 3, suf- The international aerospace community is altitude, i.e., approximately 35,786 km. More- fered unexpected, catastrophic failures while increasingly demonstrating its commitment to over, these disposal orbits should be suffi ciently still in GEO and could not be maneuvered at following GEO spacecraft disposal guidelines stable that the derelict spacecraft are not driven all. However, of the remaining 20 spacecraft, and to protecting the unique GEO regime. ♦ back within the GEO region by natural orbital all were maneuvered to higher altitude disposal PROJECT REVIEWS Flux Comparisons from the Goldstone, Haystack, and HAX Radars C. STOKELY orbital debris models. orbital debris in the LEO environment. The continual monitoring of the low NASA has been utilizing radar ob- The Goldstone radar is a bistatic X-band Earth orbit (LEO) environment using high- servations of the debris environment for radar located in the Mojave desert in Cali- ly sensitive radars is essential for an accu- over a decade from three complementary fornia at a latitude of 35.2°. The Haystack rate characterization of the dynamic debris radars: the NASA JPL Goldstone Radar, and HAX radars are, respectively, X-band environment. This environment is contin- the MIT Lincoln Laboratory (MIT/LL) and Ku-band monopulse tracking radars ually changing or evolving since there are Long Range Imaging Radar (known as the located in Tyngsboro, Massachusetts at a new debris sources and debris loss mecha- Haystack radar), and the MIT/LL Haystack latitude of 42.6°. The monopulse capabil- nisms that are dependent on the dynamic Auxilary Radar (HAX). All of these sys- ity of the Haystack and HAX radars allows space environment. Radar data are used to tems are high power radars that operate in a measurement of the position of the de- supplement, update, and validate existing a fixed staring mode to statistically sample continued on page 3 2 www.orbitaldebris.jsc.nasa.gov Flux Comparisons continued from page 2 bris within the beam, thus ensuring a more accurate estimate of the radar cross sec- tion (RCS). Each of these radars is ideally suited to measure debris within a specific size region. The Goldstone radar generally observes objects with sizes from 2 mm to 1 cm. The Haystack radar generally mea- sures from 5 mm to several meters. The HAX radar generally measures from 2 cm to several meters. These overlapping size regions allow a continuous measurement of cumulative debris flux versus diameter from 2 mm to several meters for a given altitude window. Immediately before the start of FY2003, 1 October 2002, MIT/LL had changed their Processing and Control Sys- tem (PACS) used for debris detection and near-realtime processing. This entailed replacing the analog components of their processing system with digital components along with accompanying software adjust- ments.