National Aeronautics and Space Administration Orbital Debris Quarterly News Volume 14, Issue 1 January 2010 Inside... NASA and DARPA Sponsor International Avoiding Satellite Debris Removal Conference Collisions in 2009 2 NASA and DARPA (Defense Advanced result was reinforced by the first accidental collision MMOD Inspection of Research Projects Agency) jointly sponsored between two large intact satellites, Iridium 33 and the HST Wide Field the first-of-its-kind International Conference on Cosmos 2251, in February 2009 (ODQN, April Planetary Camera 2 Orbital Debris Removal; held in Chantilly, VA, 2009, pp 1-2). These events, along with the Chinese Radiator Update 3 8-10 December 2009. Fengyun-1C anti-satellite (ASAT) test in 2007, have In 2005, NASA conducted an analysis using significantly increased the number of 10 cm and Shielding Against its long-term debris environment evolutionary larger objects in orbit and provided the impetus for Micrometeoroid and model, LEGEND, which clearly showed that the the debris removal conference (see Figure 1). Orbital Debris Impact number of debris larger than 10 cm would continue Although one of the primary goals of the with Metallic Foams 4 to increase due to collisions between existing conference was to exchange ideas for technical An Updated resident space objects, even if no new satellites were launched (ODQN, April 2006, pp 1-2). This Assessment of continued on page 2 the Orbital Debris Non-Mitigation Projection (averages and 1-ı from 100 MC runs) Environment in LEO 7 70000 Abstracts from the LEO (200-2000 km alt) NASA Orbital Debris 60000 MEO (2000-35,586 km alt) Program Office 9 GEO (35,586-35,986 km alt) Meeting Report 9 50000 Space Missions and 40000 Orbital Box Score 11 30000 20000 Effective Number of Objects (>10 cm) (>10 Objectsof Number Effective 10000 0 1950 1970 1990 2010 2030 2050 2070 2090 2110 2130 2150 2170 2190 2210 A publication of Year the NASA Orbital Figure 1. Updated (includes Fengyun-1C ASAT and Iridium/Cosmos collisions) projection of the runaway growth of Debris Program Office >10 cm resident space objects if postmission disposal measures are not implemented. Figure includes 1 σ uncertainties. Orbital Debris Quarterly News NASA-DARPA Conference continued from page 1 solutions to debris removal, the conference Solutions, and Laser Systems. the 14th Air Force’s Joint Space Operations also covered areas including economic factors In addition to the technical presentations, Center (JSpOC), who discussed Space and incentives, international legal issues, and four keynote addresses also were given. Bryan Situational Awareness. identifying stakeholders and building support O’Connor, Chief for Safety and Mission No evident consensus or conclusions were for debris removal. Assurance at NASA HQ, gave the first keynote reached at the conference. Removing existing, The conference was well attended by address on “Space Operations Safety.” Don non-cooperative objects from Earth orbit is about 275 participants from 9 foreign countries Kessler, former NASA Senior Scientist for an extremely difficult and likely expensive task. and the U.S. More than 50 presentations were Orbital Debris, presented “The Kessler Although some of the techniques for removal grouped into 10 sessions: Understanding Syndrome: Implications to Future Space discussed at the Conference have the potential the Problem, A Solution Framework, Legal Operations” during a working lunch address. On of being developed into technically feasible and Economic Issues/Incentives, Operation day 2 of the conference, Dr. Heiner Klinkrad systems, each concept seems to currently suffer Concepts, Using Environmental Forces, gave the noon keynote talk on “Space Debris from either a lack of development and testing Capturing Objects, Orbital Transfer Solutions, Environment Remediation Concepts.” The or economic viability. ♦ Technical Requirements, In Situ vs. Remote final keynote speaker was Col. Chris Moss from Avoiding Satellite Collisions in 2009 All NASA programs and projects operating recomputation of the conjunction assessment operating in concert with NASA Earth maneuverable spacecraft in low Earth orbits with updated tracking data and a shorter observation satellites (Table 1). Only two of the (LEO) or in geosynchronous orbits (GEO) propagation period (i.e., time to the encounter) maneuvers involved close approaches by intact are required to have periodic conjunction will reveal a more distant miss-distance and a vehicles (one a spacecraft and one a rocket assessments performed for the purpose of lower risk of collision. It is not uncommon for body). The other maneuvers were needed to avoiding collisions with other known resident collision avoidance maneuvers to be planned but avoid collisions with smaller debris, including space objects. These conjunction assessments canceled when new assessments are completed. twice with debris from the Chinese anti-satellite are conducted by the Joint Space Operations For example, the International Space Station test of 2007 and once with debris from the Center (JSpOC) of the U.S. Strategic Command was prepared to conduct a collision avoidance collision of the Iridium 33 and the Cosmos at Vandenberg Air Force Base in California. For maneuver on 17 March to evade a piece of debris 2251 satellites in February of 2009. the International Space Station and the Space from a former Soviet satellite which exploded in On a separate occasion in March 2009, Shuttle, these assessments are typically updated 1981. A later conjunction assessment revealed the crew of the International Space Station three times per day. For robotic satellites, which that the maneuver was not necessary. The debris had to retreat temporarily into their Soyuz normally operate at higher altitudes where reentered the Earth’s atmosphere on 4 April, return spacecraft when debris from a U.S. upper atmospheric drag effects are less pronounced, no longer posing a threat to the International stage were projected to make a close approach the assessments are updated daily, on average. Space Station or other satellites. (ODQN, Vol. 13, Issue 2, p. 3). The elliptical The conjunction assessment alert messages During 2009 conjunction assessments nature of the debris’ orbit (about 145 km by from JSpOC identify the object which is led to eight collision avoidance maneuvers by 4230 km) contributed to a late notification of expected to come near the NASA spacecraft NASA spacecraft, in addition to a collision the conjunction, leaving too little time to prepare along with information on the predicted avoidance maneuver of a French satellite for a collision avoidance maneuver. ♦ time and distance of closest approach, as well as the uncertainty associated with the TableTable 1. Collision1. Collision Avoidance Avoidance Maneuvers Maneuvers in 20092009 prediction. Typically, alert messages are issued if the calculated miss-distance is within a few Spacecraft Maneuver Date Object Avoided kilometers of the NASA spacecraft. While the TDRS 3 27 Janaury Proton rocket body sensors of the U.S. Space Surveillance Network ISS 22 March CZ-4 rocket body debris are tasked to collect additional tracking data to refine the close approach prediction, NASA Cloudsat 23 April Cosmos 2251 debris specialists compute the actual probability of EO-1 11 May Zenit rocket body debris collision. In the case of human space flight, collision avoidance maneuvers are normally ISS 17 July Proton rocket body debris conducted if the risk of collision is greater Space Shuttle 10 September ISS debris than 1 in 10,000. In general, robotic spacecraft PARASOL (France)* 29 September Fengyun-1C debris accept higher levels of risk, i.e., on the order of 1 in 1,000. Aqua 25 November Fengyun-1C debris Most alert messages do not result in Landsat 7 11 December Formosat 3D collision avoidance maneuvers. Often, a * Operating in NASA-led Earth observation network www.orbitaldebris.jsc.nasa.gov MMOD Inspection of the HST Wide Field Planetary Camera 2 Radiator Update The initial micrometeoroid and orbital debris (MMOD) impact inspection of the Hubble Space Telescope (HST) Wide Field Planetary Camera 2 (WFPC2) radiator was completed in September 2009. The task was led by the NASA Orbital Debris Program Office, with full support from the HST Program at GSFC, NASA Curation Office at JSC, NASA Hypervelocity Impact Technology Facility at JSC, and NASA Meteoroid 300.00 µm 300.00 µm Environment Office at MSFC. The objective of the inspection is to Figure 1. A typical impact crater on the WFPC2 radiator where the impacting particle did not penetrate the paint layer document and analyze the MMOD (left) and a typical crater where the impacting particle went through the paint and damaged the metal part of the impact damage on the radiator, and radiator (right). then apply the data to validate or improve the near-Earth MMOD environment definition. Two instruments were used during the 6-week inspection at GSFC – a laser scanner for a quick map of the distribution of impact features on the surface and a digital microscope for detailed two- and three-dimensional imagery of individual impacts. In addition, a laser template projector was designed and set up to record the coordinates of individual impact features. The inspection was limited to features larger than about 300 µm across, because this is approximately the threshold for the smallest MMOD particles that are important for satellite impact risk assessments. By the end of the inspection, a total of 685 MMOD impact features were identified and documented. The largest one has a crater diameter of topofthepaint 1.6 mm with a surrounding spall zone about 1.4 cm across (on the painted radiator surface). The outermost layer of the radiator is a 4-mm thick aluminum plate coated with thermal control paint. The majority of the topofthealuminum bottom ofthecrater documented impacts did not penetrate inaluminum the paint layer. The crater on the left in Figure 1 is a typical example, whereas the crater on the right shows a different Figure 2. The image and measurements of one of the MMOD impact craters on the WFPC2 radiator.