During the past two decades, great strides have been made in the international community regarding orbital debris mitigation. The majority of space-faring nations have reached a consensus on an initial set of orbital debris mitigation measures. Implementation of and compliance with the IADC and UN space debris mitigation guidelines should remain a high priority. Improvements of the IADC and UN space debris mitigation guidelines should continue as technical consensus permits. The remediation of the near-Earth space environment will require a significant and long-term undertaking

Johnson, Nicholas L.

NASA Technical Reports Server

National Aeronautics and Space Administration
Current Issues in Orbital Debris
Nicholas L. Johnson
NASA Chief Scientist for Orbital Debris
1st Canadian Workshop on Orbital Debris
St-Hubert, Quebec, Canada
21-22 June 2011
https://ntrs.nasa.gov/search.jsp?R=20110012005 2019-08-30T15:41:51+00:00Z
National Aeronautics and Space Administration
Current State of Orbital Debris    
• While the number of operational spacecraft in Earth orbit continues to 
i ( 1000) th t f th f th bit l d b i l ti increase now ~ , e ra e o  grow  o  e or a  e r s popu a on s 
even greater.
F k id t l lli i b t t l d bj t– our nown acc en a  co s ons e ween ca a oge  space o ec s
• 1810 cataloged debris (93%) from Cosmos 2251-Iridium 33 collision still in orbit; many more 
potentially hazardous debris from the event still in orbit
– Growing evidence of potentially hazardous smaller debris impacts
• Jason 1 spacecraft in 2002
O th iti id th d f bit l d b i iti ti h• n e pos ve s e, e nee  or or a  e r s m ga on measures as 
been recognized by virtually all space-faring nations and organizations.
IADC S D b i Miti ti G id li 2002–  pace e r s ga on u e nes, 
– United Nations Space Debris Mitigation Guidelines, 2007
– Increasing number of national space debris mitigation policies, guidelines, 
requirements regulations etc
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National Aeronautics and Space Administration
Issue 1: Implementation of Mitigation Guidelines      
• The IADC and UN space debris mitigation guidelines were created to assist 
t d i t ti l i ti t t bli h bit l d b igovernmen s an  n erna ona  organ za ons o es a s  or a  e r s 
mitigation policies and measures.
“I it l ti 62/217 f 22 D b 2007 th G l A bl d d th– n s reso u on  o   ecem er , e enera  ssem y en orse  e 
Space Debris Mitigation Guidelines of the Committee on the Peaceful Uses of Outer 
Space and agreed that the voluntary guidelines for the mitigation of space debris 
reflected the existing practices as developed by a number of national and international 
organizations, and invited Member States to implement those guidelines through 
relevant national mechanisms.”   
Preface, Space Debris Mitigation Guidelines of the Committee on the Peaceful Uses of Outer Space
• Within the U.S., implementation is effected via NASA standards, Department 
of Defense directives, and regulations of the FAA, FCC, and NOAA.
• Some space-faring nations and organizations have not yet adopted orbital 
debris mitigation measures consistent with the IADC and UN guidelines.
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– To the greatest extent possible, a level international playing field is needed.
National Aeronautics and Space Administration
Issue 2: Compliance with Mitigation Guidelines      
• Although the IADC and UN space debris mitigation guidelines are not 
legally enforceable, the objective of the international aerospace community 
has been that all spacecraft and launch vehicle designers and operators 
adhere to these guidelines to the greatest extent possible.
• Compliance with every guideline on every space mission is not essential for 
the preservation of near-Earth space.  However, an overall high level of 
compliance is necessary  .
• Mechanisms should be established to monitor the compliance of national 
bit l d b i iti tior a  e r s m ga on measures.
– At NASA, each space project must prepare an Orbital Debris Assessment Report at 
PDR and prior to CDR which explicitly identifies any non compliance issue         -  .
– Efforts are made through design and / or operations to resolve non-compliance issues.
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National Aeronautics and Space Administration
Issue 3:  Scope of Orbital Debris 
Mitigation Guidelines
• The IADC and UN space debris mitigation guidelines were developed to 
serve as a set of foundation guidelines and were envisioned to be 
evolutionary in light of improved understanding of the orbital debris 
environment and technological advances.
• Some nations and organizations have already implemented more 
comprehensive or detailed mitigation policies.  For example, 
– Specific postmission orbital lifetime limits in LEO (i.e., the 25-year rule)
– Specific limitations on human casualty risks following reentries
– Specific measures of effectiveness, e.g.,
• Smallest size of debris to be managed
• Limitation of probabilities of collisions with small and large debris
• Reliability of disposal operations   
• Consistent with new international consensus views, the IADC and UN space 
debris mitigation guidelines should be expanded.
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National Aeronautics and Space Administration
Issue 4: Space Vehicle Passivation     
• Both the IADC and UN space debris mitigation guidelines, as well as other 
fnational and organizational guidelines, call or the postmission passivation 
of space vehicles.
– The IADC and UN recommend that energy sources be depleted or made safe when no 
longer required for the mission.
• Some current space vehicle designs do not permit the depletion of residual            
propellants and pressurants or the disconnection of batteries from their 
charging circuits.
– Modifications of the design of these vehicles are highly desirable.
• The level at which some energy sources are “safed” (IADC) or “made safe”             
(UN) is ambiguous and has led to failures to reach consensus on the issue 
of compliance or non-compliance with these guidelines.  
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National Aeronautics and Space Administration
Issue 5: Reducing Reentry Risks     
• Although the IADC and UN space debris mitigation guidelines do not yet set 
i i k th h ld f h lti l t d t hi la max mum r s  res o  or uman casua es re a e  o space ve c e 
reentries (Issue 3), the de facto international standard is 1 in 10,000 per 
reentry event.
• For space vehicles with a mass in excess of 500 kg, achieving a human 
casualty risk of 0.0001 or less normally requires either design changes or 
adoption of controlled reentries   .
• NASA has made significant advances in the design of spacecraft to reduce 
reentry risks i e “design for demise” Examples include propellant tanks , . .,   .      
and reaction wheel assemblies, as well as simple structural members and 
ballast items.
– Many of these solutions can be applied to future space vehicle designs.
• The U S has increased the use of controlled reentries for both robotic
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spacecraft and launch vehicle orbital stages.
National Aeronautics and Space Administration
Issue 6: Small Satellites    
• IADC and UN space debris mitigation guidelines, as well as other national 
d i ti l id li li bl t ft dl fan  organ za ona  gu e nes, are app ca e o spacecra  regar ess o  
size, mass, or mission.
• To date, the operation of many small satellites (including minisats, 
microsats, nanosats, and picosats) are not in compliance with international 
orbital debris mitigation norms.
• Small satellites should not be deployed in orbits which would result in 
excessive postmission orbital lifetimes in LEO (Issue 3), particularly since 
small satellites typically have relatively short or very short operational          
lifetimes.  
– Potential solutions include postmission orbit changes (via propulsion or drag 
augmentation) or limiting operational orbits to below 700 km.        
• Concepts to deploy very large numbers (100’s or 1000’s) of small satellites 
should be carefully examined for negative environmental consequences.
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– The trackability of very small satellites should also be given serious consideration.
National Aeronautics and Space Administration
Issue 7: Improved SSA    
• Space situational awareness is important to both the characterization of 
the Earth satellite population and the safe operation of piloted and robotic 
spacecraft.
• Greater sharing of SSA information is in the interests of the entire 
aerospace community.
– The U.S. has greatly increased the scope of its already broad international SSA 
sharing efforts since 2009.
• Expanded and more sensitive SSA capabilities are needed for both the 
LEO and GEO regions.
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National Aeronautics and Space Administration
Issue 8: Space Environment Remediation     
• Numerous studies by multiple national space agencies have concluded that 
the current Earth satellite population is already unstable in some regions, 
i.e., the generation of debris from future accidental collisions will exceed 
the loss of space objects from natural orbital decay in those regions.
• The intelligent removal of large, derelict resident space objects could 
significantly curtail the long-term growth of the orbital debris population.
• To date, the technical and economic challenges of orbital debris removal 
remain great, but studies continue.
• Orbital debris removal operations will likely be accomplished as part of an 
international endeavor and will require attention to additional policy issues.
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National Aeronautics and Space Administration
Summary
• During the past two decades, great strides have been made in the 
international community regarding orbital debris mitigation.
• The majority of space-faring nations have reached a consensus on an initial 
set of orbital debris mitigation measures.
• Implementation of and compliance with the IADC and UN space debris 
mitigation guidelines should remain a high priority.
• Improvements of the IADC and UN space debris mitigation guidelines 
should continue as technical consensus permits.
• The remediation of the near-Earth space environment will require a 
significant and long-term undertaking.
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Current Issues in Orbital Debris

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