Earth’s Debris Environment

1. Earth’s Debris Environment ASEN 5335 - Aerospace Environments -- Orbital Debris

2. LEO GEO Orbit Categorizations ASEN 5335 - Aerospace Environments -- Orbital Debris

3. GEO LEO Earth’s Orbital Debris Environment • Over 18,000 objects in Earth orbit are currently tracked • An unknown number of undetectable objects of various sizes are known to exist • Earth’s atmosphere is bombarded by tons of meteoric material daily • What are the hazards ? ASEN 5335 - Aerospace Environments -- Orbital Debris

4. Space Junk: What is the Potential Damage? Size of ObjectDamage Less than 1/250 inch surface erosion Less than 1/25 inch possibly serious damage 1/8 inch ball traveling at Like a bowling ball 22,000 mph traveling @ 60 mph; (bad !) 1/2 inch aluminum ball Like a 400-lb safe traveling at 22,000 mph traveling @ 60 mph; (nasty !!) ASEN 5335 - Aerospace Environments -- Orbital Debris

5. Earth’s Orbital Debris Environment • Overview of Debris Population • Natural vs. Artificial Debris • Debris Sources and Sinks • Characterization of the Debris Environment • Detection, tracking, surveillance • Impact characterization (Gabbard diagrams) • Modeling the environment • Long Duration Exposure Facility (LDEF) • Future Trends/Mitigation Strategies ASEN 5335 - Aerospace Environments -- Orbital Debris

6. References • Johnson, N.L., and D.S. McKnight, Artificial Space Debris, Orbit Book Co., Malabar, Florida, 1991. • History of on-orbit satellite fragmentations, Orbital debris program office, N. Johnson et al., NASA Johnson Space Center, JSC 29517, LMSEAT33746, July, 2001. • The new NASA orbital debris engineering model ORDEM2002, J-C Liou et al., NASA/TP-2002-210780, May, 2002. • http://www.orbitaldebris.jsc.nasa.gov/ • http://www.aero.org/cords • http://www.wstf.nasa.gov/Hazard/Hyper ASEN 5335 - Aerospace Environments -- Orbital Debris

7. March 12, 2009 A piece of space junk nearly hits ISS • Less than 1 hour notice • 3 astronauts sought shelter in Soyuz Capsule • (kept at the station for use as a possible lifeboat • in case of emergency) • Passed within a few miles of the ISS • object about 6” long February 10, 2009 U.S. And Russian Satellites Collide • Iridium-33 (~1400 lbs) and defunct Cosmos-2251 • 790 km • > 600 pieces of debris As of 2009 there are about 18,000 pieces of orbiting debris > 10cm in size. ASEN 5335 - Aerospace Environments -- Orbital Debris

8. Current Iridium constellation with the orbits for the operational satellites shown in green, the spares shown in blue, and the inactive satellites shown in red. The Iridium 33 debris is shown in yellow and the Cosmos 2251 debris is shown in orange. ASEN 5335 - Aerospace Environments -- Orbital Debris

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11. DEBRIS Cloud Produce by 2007 Chinese ASAT Test On Jan 11, 2007, China launched a direct-ascent ASAT from Xichang Space Center against their FengYun 1C polar-orbiting weather satellite Source: http://celestrak.com/events/asat.asp ASEN 5335 - Aerospace Environments -- Orbital Debris

12. View of ISS Orbit (green) and Debris Ring (red) from Chinese ASAT Test ASEN 5335 - Aerospace Environments -- Orbital Debris

13. View of LEO Satellites (green) and Debris Ring (red) from Chinese ASAT Test ASEN 5335 - Aerospace Environments -- Orbital Debris

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15. Originate from comets, asteroids 200 kg of mass within 2000 km Largest flux below size of 0.5 mm Low densities & mass; (0.1-0.5 g cm-3) High velocity - avg 19 km s-1 Flux steady with time Affected slightly by solar cycle Quasi-isotropic flux (some Earth shielding factor) > 9000 large enough to be tracked 1.5-3.0 x 106 kg within 2000 km Largest flux above size of 1 mm Higher densities & mass; (2-9 g cm-3) Lower velocity - avg 10 km s-1 Flux increasing with time Affected by launch rate, launch operations, solar cycle Majority in high-use orbits Space Debris Overview Artificial Debris Natural Debris ASEN 5335 - Aerospace Environments -- Orbital Debris

16. Satellite Deteriorations Launch and Operations Activity Satellite Fragmentations Orbital Decay Retrieval and Deorbits Factors Affecting Satellite Population Atomic oxygen Solar Radiation SOURCES Launch rate Rocket Stages Loose Hardware Deliberate Accidental/Propulsion Collision Unknown Satellite Population SINKS Atmospheric Drag Solar-Lunar Perturbations Radiation Pressure ASEN 5335 - Aerospace Environments -- Orbital Debris

17. Artist’s conception of satellite breakup Delta 2nd Stage Stainless Steel Cylindrical Propellant Tank; landed in Georgetown, TX • Satellite Fragmentations • Fragmentation Debris -- destructive disassociation of an orbital payload, rocket body or structure -- wide range of ejecta velocities • Anomalous Debris -- result from unplanned separation of object(s) from a satellite which remains intact, i.e., deterioration of thermal blankets, protective shields, solar panels -- low relative velocities • Operational (Mission-Related) Debris -- ejected during deployment, activiation, de-orbit of payloads, manned operations, etc. ASEN 5335 - Aerospace Environments -- Orbital Debris

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19. The geosynchronous altitude population (2001) The space object environment is usually described in terms of a spatial density [1/km3] that represents an effective number of spacecraft and other objects as a function of altitude (i.e., an object in circular orbit represents much more of a collision hazard than one that occasionally traverses this region) ASEN 5335 - Aerospace Environments -- Orbital Debris

20. IRIDIUM Constellation ORBCOMM Constellation Near-earth satellite population ASEN 5335 - Aerospace Environments -- Orbital Debris

21. Orbital Debris Measurements Radar Measurements Optical Measurements Measurements of near-Earth orbital debris is accomplished by conducting ground-based and space-based measurements of the orbital debris environment. Data is acquired using ground-based radars and telescopes, space-based telescopes, and analysis of spacecraft surfaces returned from space. The data provide validation of the environment models and identify the presence of new sources. ASEN 5335 - Aerospace Environments -- Orbital Debris

22. Representative US SSN Coverage at 400 km altitude For fragmentations below about 400 km, much of the debris may reenter before detection, identification & cataloging can be completed Red: optical Blue: radar • At low altitudes (<2000 km) cataloged debris are larger than ~10 cm in diameter • At higher altitudes objects less than ~1m in diameter may be undetectable • Need for detection of smaller debris (<10 cm) in most of space ASEN 5335 - Aerospace Environments -- Orbital Debris

23. De-orbit of UARS ASEN 5335 - Aerospace Environments -- Orbital Debris

24. Orbital Reentry Survival Analysis Tool (ORSAT) ORSAT is the NASA code for predicting reentry survivability of objects entering from orbital decay or from controlled entry. Prediction of survivability is required in order to determine the risk to humans on the ground. This impact risk, which is based on the predicted total debris casualty area, orbit inclination, and year of reentry, should be less than 1:10,000. Example of ORSAT used in predicting the UARS reentry breakup. Demise altitude vs. downrange evaluated for nearly all of the UARS components. ASEN 5335 - Aerospace Environments -- Orbital Debris

25. Recovered Orbital Debris On average, one non-functional spacecraft, launch vehicle orbital stage, or other piece of cataloged debris has fallen back to Earth every day for more than 40 years. The majority of these objects do not survive the intense reentry environment. For the minority which do survive in whole or in part, most fall harmlessly into the oceans or onto sparsely populated regions This 30 kg titanium pressurant tank also survived the reentry of the Delta 2 second stage on 22 January 1997 but was found farther downrange near Seguin, TX. Another Delta 2 second stage reentered on 27 April 2000 over South Africa. In this incident, three objects were recovered along a path nearly 100 km long: the main stainless steel propellant tank, a titanium pressurant tank, and a portion of the main engine nozzle assembly. On 21 January 2001, a Delta 2 third stage, known as a PAM-D (Payload Assist Module - Delta), reentered the atmosphere over the Middle East. The titanium motor casing of the PAM-D, weighing about 70 kg, landed in Saudi Arabia about 240 km from the capital of Riyadh. This is the main propellant tank of the second stage of a Delta 2 launch vehicle which landed near Georgetown, TX, on 22 January 1997. This approximately 250 kg tank is primarily a stainless steel structure and survived reentry relatively intact. ASEN 5335 - Aerospace Environments -- Orbital Debris

26. Hypervelocity Impact Measurements • Hypervelocity impact measurements are used to • assess the risk presented by orbital debris to operating spacecraft and to • develop new materials and new designs to provide better protection from the environment with less weight penalty. • The data from this work provides • analysis and interpretation of impact features on returned spacecraft surfaces. • data needed to improve models • recommendations on design and operations procedures to reduce risk • The primary facility for this research is the Hypervelocity Impact Technology Facility (HIT-F) at NASA/JSC in Houston, although there are other facilities at JSC, New Mexico, and various DoD laboratories. Hypervelocity Impact Measurements Long Duration Exposure Facility (LDEF) ASEN 5335 - Aerospace Environments -- Orbital Debris

27. Orbital Debris Mitigation • Mitigation measures can take the form of • curtailing or preventing the creation of new debris, • designing satellites to withstand impacts by small debris, • utilizing orbital regimes with less debris, • adopting specific spacecraft attitudes, • maneuvering to avoid collisions with debris. • developing debris-clearing strategies • All NASA flight projects are now required to provide debris assessments as a normal part of the project development. • Alternatives are under consideration for controlling the risk to operating spacecraft, which includes both spacecraft protection and debris environment control. Debris clearing via laser beam-induced impulse ASEN 5335 - Aerospace Environments -- Orbital Debris