Debris Remediation
In the past, NASA’s ODPO has emphasized avoiding the creation of orbital debris through mitigation techniques.
However, in 2005, a
study by the ODPO
that used the LEGEND model showed that even if no future
launches occurred, collisions between existing satellites would increase the 10-cm and larger debris population
faster than atmospheric drag would remove objects. The "No New Launches" scenario highlights the eventual need for
remediation of the existing debris population (also known as active debris removal, or ADR). The potential for
collisions to damage the space environment was underscored by the Chinese ASAT test in 2007 and the accidental
collision between Cosmos 2251 and Iridium 33 in 2009
(ODQN 14-4,
ODQN 14-2,
ODQN 13-2,
ODQN 13-1,
ODQN 12-1,
and ODQN 11-2).
These two events increased the SSN tracked orbital population by almost one third.
If the goal of remediation is to reduce the risk to the current fleet of operational spacecraft, remediation
techniques need to focus on removal of small sized (but still damaging) debris. If the goal is to control the
long-term growth of the debris population, ADR techniques need to concentrate on the removal of large, massive
objects such as intact rocket bodies and non-functional satellites. These massive objects are the long-term
source of fragmentation debris from on-orbit explosions and collisions. Studies have indicated that the removal
of as few as five of the highest risk objects (defined as mass times probability of collision) per year can
stabilize the long-term low Earth orbit debris environment
(ODQN 15-3,
ODQN 15-2).
Any successful ADR concept must be technologically feasible, economically affordable, and politically acceptable
to the international community. In addition, debris removal activities should also be accomplished in a manner
that does not unduly increase hazards to people and property on Earth from reentering debris.
The June 2010 National Space Policy for the United States of America directs NASA and the Department of Defense
to "Pursue research and development of technologies and techniques… to mitigate and remove on-orbit debris…"
However, it should be noted that, currently, no U.S. government entity has been assigned the task of removing
existing on-orbit debris. The June 2018 Space Policy Directive-3, the National Space Traffic Management Policy,
also states that "The United States should pursue active debris removal as a necessary long- term approach to
ensure the safety of flight operations in key orbital regimes. This effort should not detract from continuing
to advance international protocols for debris mitigation associated with current programs."