The Characteristics and Consequences of the Break-up of the Fengyun-1C Spacecraft N. Johnson, E. Stansbery, J.-C. Liou, M. Horstman, C. Stokely, D. Whitlock NASA Orbital Debris Program Office NASA Johnson Space Center 58 th International Astronautical Congress 24-28 September 2007
Outline Background of Breakup Event Debris Cloud Characterization U.S. Space Surveillance Network data Special Haystack radar observations Changes in the near-earth Environment Near- and Long-term Collision Effects Conclusions 2 58 th International Astronautical Congress
Breakup Event Summary The Fengyun-1C spacecraft (1999-025A, U.S. Satellite Number 25730) was the target on 11 January 2007 of a ground-launched, direct ascent ballistic missile equipped with a kinetic kill vehicle. Fengyun-1C orbit: ~ 850 km, 98.6 deg inclination Fengyun-1C mass: ~960 kg Impact velocity: ~ 9 km/s 3 58 th International Astronautical Congress
SSN Observations of Debris Cloud Six months after the breakup, a total of 1967 pieces of debris had been officially cataloged by the U.S. Space Surveillance Network. ~ 400 additional debris were being tracked but not yet cataloged. 4000 3500 3000 2500 Apogee Perigee 11 July 2007 Orbital Period of Parent Altitude (km) 2000 1500 Slight posigrade asymmetry (60/40) in the heart of the cloud 1000 500 0 90 95 100 105 110 115 120 125 130 135 140 Period (min) 4 58 th International Astronautical Congress
SSN Observations of Debris Cloud (continued) A greater asymmetry is seen in the debris inclinations; approximately 80% of the debris have inclinations greater than those of Fengyun-1C prior to the intercept. 104 103 102 101 Inclination (deg) 100 99 98 97 96 95 90 95 100 105 110 115 120 125 130 135 140 Period (min) 5 58 th International Astronautical Congress
SSN Observations of Debris Cloud (continued) Preliminary analysis of 1600 debris indicates area-to-mass ratios on average greater than predicted by the NASA standard breakup model for a hypervelocity collision. Verification of conversation from RCS to characteristic length is continuing. 1.E+02 1.E+01 1.E+00 A/M (m 2 /kg) 1.E-01 1.E-02 1.E-03 0 0.1 0.2 0.3 0.4 0.5 0.6 Characteristic Length (m) 6 58 th International Astronautical Congress
Haystack Observations of Debris Cloud The Haystack radar observed the debris cloud for 1.9 hours in a special orbit plane tracking mode ~24 hours after the breakup. Some sub-centimeter debris were observed. 1000 1800 1600 1400 Count 100 10 Altitude (km) 1200 1000 800 600 400 200 1 0.001 0.01 0.1 1 Characteristic Length (m) 0 20.0 20.5 21.0 21.5 22.0 GMT Time of Day (hrs) 7 58 th International Astronautical Congress
Haystack Observations of Debris Cloud (continued) During January through May, Haystack observed the debris in a normal staring mode for 184 hours. 140 120 Approximate time of parent orbit plane crossing Inclination (deg) 100 80 Haystack not operated during this time window 60 40 0 3 6 9 12 15 18 21 24 GMT Time of Day (hrs) 8 58 th International Astronautical Congress
Changes in the near-earth Environment The number of tracked objects in LEO increased ~ one-third as a result of the breakup of Fengyun-1C. The debris now represents a significant portion of conjunction assessments for many operational spacecraft. A least two U.S. spacecraft have maneuvered to avoid very close approaches of tracked debris, and the ISS canceled a planned collision avoidance maneuver when the estimated miss distance increased to an acceptable value shortly before the conjunction. 1300 Effective Number of Objects per 50 km Bin 1200 1100 1000 900 800 700 600 500 400 300 200 100 Tracked objects (1 June, 2007) Tracked objects (1 January, 2007) Fengyun-1C fragments 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Altitude (km) 9 58 th International Astronautical Congress
Evolution of Debris Orbit Planes 10 58 th International Astronautical Congress
Projected Debris Decay Rate Due to the apparent higher than expected debris area-to-mass ratios, the orbital decay rates will likewise be accelerated. However, the greater than expected number of large debris yields a lifetime large debris collision risk for the cloud of essentially the same magnitude. For smaller debris collision risks may be greater than model predictions. 100 Percent of Debris Cloud Remaining in Orbit 90 80 70 60 50 40 30 20 10 Projected decay based upon standard model Projected decay based upon preliminary observations 0 0 10 20 30 40 50 60 70 80 90 100 Years since the Event 11 58 th International Astronautical Congress
Long-term Effects on the Environment NASA s evolutionary satellite population model LEGEND was employed to predict the possible increase in the long-term large object population resulting from the Fengyun-1C debris cloud. 30000 Effective Number of Objects (>10 cm) in LEO 25000 20000 15000 10000 5000 With Chinese ASAT debris Without Chinese ASAT debris 0 1950 1970 1990 2010 2030 2050 2070 2090 2110 12 58 th International Astronautical Congress
Summary The breakup of Fengyun-1C stands as the most severe satellite fragmentation of the space age, and its detrimental effects will be very longlasting. In analyses to date, the number of debris greater than 10 cm produced appears to markedly exceed the number predicted by the NASA standard breakup model for hypervelocity collisions. An assessment of the number of actual debris 1 cm and larger is still underway. Both the IADC Space Debris Mitigation Guidelines and the UN COPUOS Space Debris Mitigation Guidelines explicitly recommend the avoidance of any intentional destruction which would result in long-lived debris. The test involving Fengyun-1C is non-compliant with those recommendations. 13 58 th International Astronautical Congress