National Aeronautics and Space Administration U.S. Space Debris Environment, Operations, and Research Updates J.-C. Liou, Ph.D. Chief Scientist for Orbital Debris National Aeronautics and Space Administration United States 55th Session of the Scientific and Technical Subcommittee Committee on the Peaceful Uses of Outer Space, United Nations 29 January – 9 February 2018, Vienna National Aeronautics and Space Administration Presentation Outline • Space Missions in 2017 • Earth Satellite Population • Collision Avoidance Maneuvers • Postmission Disposal of U.S. Spacecraft • Space Situational Awareness (SSA) and the Space Debris Sensor (SDS) 2/12 National Aeronautics and Space Administration Worldwide Space Activity in 2017 • A total of 86 space launches placed more than 400 spacecraft into Earth orbits during 2017, following the trend of increase over the past decade 140 120 100 80 60 40 20 Worldwide LaunchesWorldwide (Earth Orbit orBeyond) 0 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 3/12 • Number of Objects 10000 12000 14000 16000 18000 20000 National Aeronautics and Space Administration Space and Aeronautics National objects Earth orbitcontinued in to increase 2017 in According Satellite to theCatalog, U.S. the number of10 cm andlarger 2000 4000 6000 8000 Evolution of the Cataloged Satellite Population 0 1956 1958 1960 Mission-relatedDebris Rocket Bodies Spacecraft Fragmentation Debris TotalObjects 1962 1964 1966 1968 1970 1972 1974 1976 1978 1980 Iridiumand 33 Collision2251 Cosmos of 1982 4 Year /12 1984 1986 Destruction of Fengyun 1988 1990 1992 1994 1996 1998 2000 - 2002 1C 2004 2006 2008 2010 are operational ~1700 2012 2014 2016 2018 • National Aeronautics and Space Administration Space and Aeronautics National Mass in Orbit (metric tons) Thetotal mass ofmaterial exceeded 7600 metric 2017 tonsin Mass in Near 1000 2000 3000 4000 5000 6000 7000 8000 0 1956 1958 1960 1962 1964 Debris Mission-related Fragmentation Debris Rocket Bodies Spacecraft Total Objects 1966 - 1968 Increase to Earth Continued Space 1970 1972 1974 1976 1978 1980 Year 5 1982 /12 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016 2018 National Aeronautics and Space Administration International Space Station and NASA Robotic Spacecraft Collision Avoidance Maneuvers • NASA has established conjunction assessment processes for its human spaceflight and uncrewed spacecraft to avoid accidental collisions with objects tracked by the U.S. Space Surveillance Network (SSN) – NASA also assists other U.S. government spacecraft owners with conjunction assessments and subsequent maneuvers • The International Space Station (ISS) has conducted 25 debris collision avoidance maneuvers since 1999 – None in 2016-2017, but an ISS visiting vehicle had one collision avoidance maneuver in 2017 • During 2017 NASA executed or assisted in the execution of 21 collision avoidance maneuvers by uncrewed spacecraft – Four maneuvers were conducted to avoid debris from Fengyun-1C – Two maneuvers were conducted to avoid debris from the collision of Cosmos 2251 and Iridium 33 – One maneuver was conducted to avoid the ISS 6/12 National Aeronautics and Space Administration Disposal of U.S. Spacecraft in GEO • Two U.S. commercial spacecraft ended operations in GEO in 2017 – Intelsat 701 and EchoStar 3 were launched before the establishment of the 2007 UN COPUOS Space Debris Mitigation Guidelines – Both spacecraft conducted disposal maneuvers to move away from the GEO region and postmission passivation operations (fuel depletion, discharging batteries), consistent with the UN COPUOS Space Debris Mitigation Guidelines • A third spacecraft, AMC-9, launched in 2003, was forced to end its mission after a serious anomaly – The operator was able to regain partial control of the spacecraft, raised its orbit away from GEO, and carried out several passivation operations International Minimum Height Maximum Height Spacecraft Designator above GEO above GEO Intelsat 701 1993-066A 264 km 279 km EchoStar 3 1997-059A 350 km 440 km AMC-9 2003-024A 277 km 430 km 7/12 National Aeronautics and Space Administration Iridium System Satellite Replacement and Disposal in LEO • In 2017, the operator of the 66 spacecraft Iridium constellation began replacement of spacecraft – Forty new spacecraft (“Iridium NEXT”) were launched in 2017 – Thirteen first-generation spacecraft were removed from operational orbits for disposal and passivation, consistent with the UN COPUOS Space Debris Mitigation Guidelines • Six decayed from orbit and reentered so far, three are expected to reenter by 2020, and the remaining four are expected to reenter within 25 years • As newly launched spacecraft enter into service, additional first- generation Iridium spacecraft will be removed from orbit for disposal Successful launch of the 4th Iridium NEXT mission on 22 December 2017. 8/12 National Aeronautics and Space Administration Space Situational Awareness in the United States • The U.S. Strategic Command (USSTRATCOM) continues to use the SSN to track the largest objects in the near-Earth environment – Objects approximately 10 cm and larger in low Earth orbit (LEO) – Objects approximately 1 m and larger in geosynchronous Earth orbit (GEO) – USSTRATCOM shares the SSA data with the global community via SSA Sharing Agreements and the space-track.org website • NASA uses additional radars, telescopes, and in-situ measurements to characterize objects too small to be tracked by the SSN, but large enough to threaten human spaceflight and robotic missions – Millimeter-sized debris represent the highest penetration risk to most operational spacecraft in LEO – NASA uses all available measurement data to develop the Orbital Debris Engineering Model (ORDEM) for mission impact risk assessments. The model is available at the NASA Orbital Debris Program Office’s website 9/12 National Aeronautics and Space Administration SSA Coverage in the United States 36,000 ES-MCAT (2018- ) MODEST (04-14) 10,000 Goldstone radars (>32.2º) HUSIR (Haystack radar) (>30º) 2000 Data Gap 1000 HST-WFPC2 (580x610 km, 93-09) USSTRATCOM Space Surveillance Network STS (95-11), SDS (2018-2020) Haystack Auxiliary (HAX) radar (>42.6º) 100 10 µm 100 µm 1 mm 1 cm 10 cm 1 m 10 m Particle Size (Boundaries are notional) 10/12 National Aeronautics and Space Administration Top Risk for Operational Spacecraft in LEO • The 2014-15 NASA Engineering and Safety Center study on the micrometeoroid and orbital debris assessment for the Joint Polar Satellite System provided the following findings – Millimeter-sized orbital debris pose the highest penetration risk to most operational spacecraft in LEO – The most effective means to collect direct measurement data on millimeter- sized debris above 600 km altitude is to conduct in situ measurements – There is currently no in situ data on such small debris above 600 km altitude • Since the orbital debris population follows a power-law size distribution, there are many more millimeter-sized debris than the large tracked objects – Current conjunction assessments and collision avoidance maneuvers against the tracked objects (which are typically 10 cm and larger) only address a small fraction (<1%) of the mission-ending risk from orbital debris • To address the millimeter-sized debris data gap above 600 km, NASA has recently developed an innovative in situ measurement instrument – the Space Debris Sensor (SDS) 11/12 National Aeronautics and Space Administration Measurements of Small Debris from the ISS • SpaceX-13, carrying resupply and NASA’s SDS, was launched to the ISS on 15 December 2017 – The SDS mission will mature NASA’s in situ measurement technologies and collect data on the sub-millimeter debris population at the ISS altitude – NASA will seek future mission opportunities to deploy SDS above 600 km altitude to fill the data gap on the millimeter-sized orbital debris for better SSA and reliable orbital debris impact risk assessments to improve the safe operations of spacecraft in LEO ISS MAGIK SpaceX-13 launch Animation SDS Columbus SpaceX-13 launch SDS SpaceX Dragon trunk 12/12.