NASA Policy and Considerations Related to Orbital Debris

1

• NASA Policy and Considerations Related to Orbital
  Debris

Information provided by Nicholas Johnson at JSC,
and all information is available from public
resources
2
What is Orbital Debris?

• Space debris encompasses both natural (meteoroid)
  and artificial (man-made) particles.
• Meteoroids are in orbit about the Sun
• Orbital debris are man-made and in orbit about
  the Earth

Non-operational Spacecraft
Fragmentation and Mission-related Debris
Derelict Launch Vehicle Stages
3


Orbital Debris Detectors and Damage Potential
Potential Shuttle Damage

4
International Academy of Astronautics

• The IAA, established in 1960, is a professional
  organization of approximately 1200 individuals
  with demonstrated expertise in one or more fields
  of astronautics.
• The IAA published its first position paper on
  space debris in 1995. This was updated in
  2000-2001.
• The position paper includes a section on
  Implementation of Debris Control Methods
• A new Position Paper on Space Debris Mitigation
  was released in 2005.
• This position paper addresses space debris issues
  and recommended mitigation measures separately
  for spacecraft and launch vehicles.

5
Inter-Agency Space Debris Coordination Committee
(IADC)

• Established in 1993
• To exchange information on space debris research
  activities between member space agencies
• To facilitate opportunities for cooperation in
  space debris research
• To review progress of ongoing cooperative
  activities and
• To identify debris mitigation options
• 11 members include all leading space agencies in
  the world from China, France, Germany, India,
  Italy, Japan, Russia, Ukraine, United Kingdom,
  and the United States, as well as ESA.
• NASA delegation includes personnel from DoD,
  State, and the FCC
• Developed consensus international orbital debris
  mitigation guidelines in October 2002 presented
  to the United Nations in February 2003.

Website www.iadc-online.org
6
Orbital Debris at the United Nations

• Since 1994 the subject of orbital debris has been
  on the agenda of the Scientific and Technical
  Subcommittee (STSC) of the United Nations
  Committee on the Peaceful Uses of Outer Space
  (COPUOS).
• A multi-year work plan culminated in the 1999
  Technical Report on Space Debris
  (A/AC.105/720), summarizing the world
  state-of-knowledge concerning measurements and
  modeling of the environment as well as identified
  orbital debris mitigation measures.
• The IADC Space Debris Mitigation Guidelines were
  reviewed and discussed at STSC in both 2003 and
  2004.
• During 2005 and 2006 a special STSC Working Group
  prepared draft Space Debris Mitigation
  Guidelines of the STSC of the COPUOS.
• Space Debris Mitigation Guidelines adopted by
  consensus of the STSC of COPUOS on 21 February
  2007.
• Full COPUOS approval anticipated in June 2007

7
Other Considerations

• Our debris tracking policy and decision process
  for doing avoidance maneuvers
• NASA conducts conjunction assessments and, as
  necessary, collision avoidance maneuvers for the
  Space Shuttle, ISS, a number of LEO robotic
  spacecraft, and the TDRS constellation. 
• The decision to conduct a collision avoidance
  maneuver is based upon either a discrete
  probability of collision (e.g., in excess of 1 in
  10,000) or on an established miss distance.  The
  geometry of the conjunction is also taken into
  account.
• Size of debris we/Space Command are able to track
• The U.S. Space Surveillance Network (SSN),
  managed by U.S. Strategic Command, maintains a
  Satellite Catalog which is nearly complete for
  objects larger than 10 cm in LEO and larger than
  1 m in GEO. 
• At ISS altitudes, the SSN can track objects as
  small as 5 cm.
• How often do we check for possible collisions
• For human space flight operations, conjunction
  assessments are performed multiple times per day,
  normally looking three days into the future. 
• For robotic spacecraft, the conjunction
  assessments are performed less frequently but for
  longer prediction periods. 
• What and when do we share this information with
  our International Partners
• Conjunction information for ISS is shared with
  our Russian colleagues since they would be
  involved in executing a collision avoidance
  maneuver. 
• With only a very few exceptions, NASA is not
  involved in conjunction assessments for foreign
  spacecraft operators.

8
Other Considerations (Cont)

• What we perceive as the real risks or
  probabilities of impact to our spacecraft
• The level of collision risk to spacecraft varies
  greatly on their size and altitude. 
• We can mitigate the risks from debris larger than
  5-10 cm by collision avoidance. 
• We can mitigate the risks from debris smaller
  than 1 cm by shielding (in most cases). 
• For debris in between, our only option is to
  curtail the growth of that debris population.
• Chinese ASAT test
• The Chinese ASAT test in January 2007 created the
  largest debris cloud known to date. 
• Not only does the debris range through all of LEO
  (actually up to 4000 km), but also most of the
  debris will be very long-lived, many decades to a
  century or more. 
• The SSN is now tracking more than 1600 debris a
  total of 1257 had been officially cataloged as of
  1 April. 
• The risk to ISS from the Chinese debris spiked
  immediately after the test and has now dropped
  below normal background levels.
• To date, no avoidance maneuvers have been
  required of the ISS due this ASAT test