National Aeronautics and Space Administration Orbital Debris Quarterly News Volume 11, Issue 3 July 2007 UN Committee Accepts Space Debris Mitigation Guidelines Inside... In February 2007 the Scientific and Technical uses of outer space, to devise programs in this field Subcommittee (STSC) of the United Nations’ to be undertaken under the auspices of the United Investigation of MMOD Committee on the Peaceful Uses of Outer Space Nations, to encourage continued research and Impact on STS-115 (COPUOS) completed a multi-year work plan with the dissemination of information on outer space Shuttle Payload the adoption of a consensus set of space debris matters, and to study legal problems arising from mitigation guidelines (Orbital Debris Quarterly the exploration of outer space. The membership of Bay Door2 News, 11-2, p.1). The full COPUOS, at its latest COPUOS now includes 67 Member States. meeting in Vienna, Austria, during 6-15 June, has The STSC will continue to include space debris Optical Observations also accepted these guidelines. as an agenda item for its annual meetings. Beginning of GEO Debris with COPUOS was established by the United in 2008 Member States are encouraged to report Two Telescopes ���������6 Nations General Assembly in 1959 to review the their progress in implementing the new UN space scope of international cooperation in the peaceful debris mitigation guidelines. ♦ Optical Measurement Center Status �������������7 Disposal of Spacecraft Detection of Debris from Chinese ASAT Test and Launch Vehicle Increases; One Minor Fragmentation Event Stages in LEO ������������8 GEO Population in Second Quarter of 2007 Estimates Using The extent of the debris cloud created by the increase of fragmentation debris in Earth orbit of Optical Survey destruction of the Fengyun-1C meteorological an estimated 75% (Figure 1). Data �����������������������������9 satellite on 11 January 2007 by a Chinese ballistic The Fengyun-1C debris cloud extends from interceptor is becoming more apparent as routine 200 km to 4000 km in altitude, with the highest Space Missions and and special radar observations of the fragments continued on page provide more data. By the Orbital Box Score ����10 7000 end of June 2007 the U.S. Space Surveillance Network 6000 (SSN) was tracking more than 2200 objects with a size 5000 of at least 5 cm. 4000 More than 1900 of these debris had been 3000 officially cataloged, making the event by far the worst 2000 satellite fragmentation of the space age. The Chinese 1000 anti-satellite (ASAT) test 0 7 9 1 3 5 7 9 1 3 5 7 9 1 3 5 7 9 1 3 5 7 9 1 3 5 7 5 5 6 6 6 6 6 7 7 7 7 7 8 8 8 8 8 9 9 9 9 9 0 0 0 0 A publication of 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 0 0 0 0 coupled with other satellite 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 2 2 2 Year The NASA Orbital breakups in the first quarter of the year has resulted in an Figure 1. The total number of known fragmentation debris in Earth orbit increased by Debris Program Office about 75% during the first quarter of 2007. Orbital Debris Quarterly News Detection of Debris continued from page 1 of only one or a few debris with very small 31405), and it is likely to have also separated separation velocities. The debris appear to from Vanguard 3 in 2006, possibly about the “fall-off” their parent satellites, probably due time of the first piece. The newly discovered to environmental degradation or small particle debris is decaying at a slower pace than the impacts (Johnson, 2004). debris seen last year, but both are falling back In April a new piece (U.S. Satellite to earth much faster than Vanguard 3 from its Number 31408) from the derelict U.S. Seasat orbit of 500 km by 3300 km. spacecraft (International Designator 1978- 064A, U.S. Satellite Number 10967) was 1. Johnson, N.L., “environmentally-Induced detected. This was the 15th debris from Seasat debris Sources”, Advances in Space Research, cataloged since 1983 and the fourth seen Vol. 34 (2004), Issue 5, pp. 993-999. ♦ during the past four years (Figure 3). These debris exhibit a variety of ballistic coefficients, Figure . The debris cloud from the Fengyun-1C spacecraft is rapidly dispersing. but all decay relatively rapidly compared to Seasat itself, which is in a stable, nearly circular concentration near the breakup altitude of orbit near 750 km. Additional debris have approximately 850 km. The debris orbits are been briefly detected rapidly spreading (Figure 2) and will essentially from Seasat, but they encircle the globe by the end of the year. Only have reentered prior 101 a few known debris had reentered more than to being cataloged. Seasat five months after the test, and the majority will The source of the 100 27889 31408 remain in orbit for many decades. debris could be 99 The large number of debris from either the spacecraft 28843 98 Fengyun-1C are posing greater collision or the Agena upper 28143 ) risks for spacecraft operating in low Earth stage to which it is n i 97 m orbit. The number of close approaches has still attached. ( d o i 96 risen significantly. On 22 June, NASA’s Terra early in 2006 r e spacecraft had to execute a collision avoidance an anomalous event P 95 maneuver to evade a fragment from Fengyun- involving the 46- 1C that was on a trajectory which would have year-old Vanguard 3 94 passed within 19 meters of Terra. was detected (Orbital After a flurry of satellite breakups in Debris Quarterly 93 the first quarter of 2007, the next three months News, 10-3, p. 2). 92 witnessed only one minor fragmentation A second piece has 2003 2004 2005 2006 2007 classified as an anomalous event. An anomalous now been cataloged event is normally characterized by the release (U.S. Satellite Number Figure 3. A new piece of debris separated from the Seasat spacecraft in early 2007. PROJECT REVIEWS Investigation of MMOD Impact on sts-115 Shuttle Payload Bay Door Radiator J. Hyde, e. CHristianseN, d. LeAr, J. 2024-T81 facesheets Kerr, F. Lyons, J. Yasensky and Al5056-H39 cores. The face- 1. Introduction sheets are topped The Orbiter radiator system consists of with 0.005 in. eight individual 4.6 m x 3.2 m panels located (0.127 mm) silver- with four on each payload bay door. Forward Teflon tape. The panels #1 and #2 are 2.3 cm thick while the radiators are located aft panels #3 and #4 have a smaller overall on the inside of thickness of 1.3 cm. The honeycomb radiator the shuttle payload panels consist of 0.028 cm thick Aluminum continued on page Figure 1 Cross section of orbiter radiator facesheet. wwworbitaldebrisjscnasagov MMOD Impact continued from page bay doors, which are closed during ascent and observations revealed reentry, limiting damage to the on-orbit portion exit damage on the of the mission. rear facesheet. Impact Through crack of damage features on the inner face sheet 2. Post Flight Inspection rear facesheet included Post-flight inspections at the Kennedy Space a 0.03 in. diameter hole Center (KSC) following the STS-115 mission (0.76 mm), a ~0.05 in. Crack length, 0.267” revealed a large micrometeoroid/orbital debris tall bulge (~1.3 mm), (MMOD) impact near the hinge line on the and a larger ~0.2 in. tall #4 starboard payload bay door radiator panel. bulge (~5.1 mm) that FWD The features of this impact make it the largest exhibited a crack over ever recorded on an orbiter payload bay door 0.27 in. (6.8 mm) long. radiator. The general location of the damage A large ~1 in. (25 mm) site and the adjacent radiator panels can be seen diameter region of the in Figure 2. Initial measurements of the defect honeycomb core was Hole, 0.031” indicated that the hole in the facesheet was also damaged. refer to 0.108 in. (2.74 mm) in diameter. Figure 3 shows Figure 4 for an image All measurements ± 0.005” an image of the front side damage. Subsequent of the backside damage continued on page 4 Figure 4. Rear facesheet damage on starboard radiator #4. 0.4in (10.2mm) IMPACT LOCATION Panel 4 Hinge Line Panel 3 0.85in (21.6mm) Panel 2 Panel 1 1.1in (27.9mm) Figure . Orbiter payload bay door radiators (starboard panels 1-4 shown). Figure 5. Front facesheet with thermal tape removed. Extent of damaged facesheet is hghlighted. Figure 6. SEM images of hole in front facesheet. Asymmetric nature of lip can be Figure . Front facesheet damage on starboard radiator #4. seen in the oblique view. Orbital Debris Quarterly News MMOD Impact continued from page entry hole in the facesheet. The asymmetric height of the lip may be attributed to projectile shape and impact angle. Numerous instances of a glass-fiber organic matrix composite were observed in the facesheet tape sample. The fibers were approximately 10 micrometers in diameter and variable lengths. EDS analysis indicated a composition of Mg, Ca, Al, Si, and O. Figures 7 and 8 present images of the fiber bundles, which were believed to be circuit board material based on similarity in fiber diameter, orientation, consistency, and composition. 4. Hypervelocity Impact Tests A test program was initiated in an attempt to simulate the observed damage to the radiator facesheet and honeycomb.