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

ASEN Aerospace Environments -- Orbital Debris 2 LEOGEO Orbit Categorizations

ASEN Aerospace Environments -- Orbital Debris 3 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 ? LEO GEO

ASEN Aerospace Environments -- Orbital Debris 4 Space Junk: Size of Object Damage Less than 1/250 inchsurface erosion Less than 1/25 inchpossibly serious damage 1/8 inch ball traveling atLike a bowling ball 22, mph; (bad !) 1/2 inch aluminum ballLike a 400-lb safe traveling at 22, mph; (nasty !!) What is the Potential Damage?

ASEN Aerospace Environments -- Orbital Debris 5 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 Earth’s Orbital Debris Environment

ASEN Aerospace Environments -- Orbital Debris 6 References Johnson, N.L., and D.S. McKnight, Artificial Space Debris, Orbit Book Co., Malabar, Florida, History of on-orbit satellite fragmentations, Orbital debris program office, N. Johnson et al., NASA Johnson Space Center, JSC 29517, LMSEAT33746, July, The new NASA orbital debris engineering model ORDEM2002, J-C Liou et al., NASA/TP , May,

ASEN 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 km > 600 pieces of debris As of 2009 there are about 18,000 pieces of orbiting debris > 10cm in size.

ASEN 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.

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

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

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

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ASEN Aerospace Environments -- Orbital Debris 15 Space Debris Overview Originate from comets, asteroids 200 kg of mass within 2000 km Largest flux below size of 0.5 mm Low densities & mass; ( 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 x 10 6 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 Natural Debris Artificial Debris

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

ASEN Aerospace Environments -- Orbital Debris 17 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. Artist’s conception of satellite breakup Delta 2nd Stage Stainless Steel Cylindrical Propellant Tank; landed in Georgetown, TX

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ASEN Aerospace Environments -- Orbital Debris 19 The space object environment is usually described in terms of a spatial density [1/km 3 ] 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) The geosynchronous altitude population (2001)

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

ASEN Aerospace Environments -- Orbital Debris 21 Orbital Debris Measurements Optical MeasurementsRadar 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 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 Aerospace Environments -- Orbital Debris 23 De-orbit of UARS

ASEN 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 Aerospace Environments -- Orbital Debris 25 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 This approximately 250 kg tank is primarily a stainless steel structure and survived reentry relatively intact. 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. 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 Recovered Orbital Debris

ASEN Aerospace Environments -- Orbital Debris 26 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) Hypervelocity Impact Measurements

ASEN Aerospace Environments -- Orbital Debris 27 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. Orbital Debris Mitigation Debris clearing via laser beam-induced impulse