Status Report

NASA OIG: NASA’s Efforts to Mitigate the Risks Posed by Orbital Debris

By SpaceRef Editor
January 27, 2021
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NASA OIG: NASA’s Efforts to Mitigate the Risks Posed by Orbital Debris

Full report


Orbital debris is defined as human-made objects in space that no longer serve a useful purpose, such as decommissioned satellites and parts of spacecraft. This debris—also known as “space junk”—lingers above the Earth’s atmosphere for years until it decays, deorbits, explodes, or collides with another object thus creating more debris. The amount of orbital debris has increased exponentially over the last 60 years due to (1) accumulating and increasing amounts of satellites and other objects launched into space by public, civil, and private entities from around the globe and (2) intentional and accidental spacecraft explosions and collisions.

Millions of pieces of orbital debris exist in low Earth orbit (LEO)—at least 26,000 the size of a softball or larger that could destroy a satellite on impact; over 500,000 the size of a marble big enough to cause damage to spacecraft or satellites; and over 100 million the size of a grain of salt that could puncture a spacesuit. Moreover, the growing volume of orbital debris threatens the loss of important space-based applications used in daily life, such as weather forecasting, telecommunications, and global positioning systems that are dependent on a stable space environment. At NASA, the Orbital Debris Program Office (ODPO), funded by the Office of Safety and Mission Assurance, has taken the national and international lead in conducting measurements of the debris environment and in developing the technical consensus for adopting mitigation measures.

In this audit, we evaluated NASA’s efforts to mitigate the risks posed by orbital debris as well as the Agency’s coordination and communication efforts with international and commercial organizations to address the issue. To complete this work, we interviewed representatives from NASA, the U.S. Department of Defense (DOD), and the commercial sector; reviewed federal laws, regulations, policies, and reports related to orbital debris; and assessed a sample of Orbital Debris Assessment Reports (ODAR), End of Mission Plans (EOMP), and supporting documentation to ensure they met NASA requirements.


Given the rapid increase of space activity worldwide and the current state of orbital debris in LEO, international space agencies and the scientific community agree that mitigation-only activities focused solely on prevention are not sufficient to stabilize the orbital debris environment. Rather, to effectively address the orbital debris issue, global mitigation and strategic remediation efforts are necessary. Multiple studies have found that the growth of debris in LEO can be slowed by ensuring that at least 90 percent of all spacecraft are removed from orbit within 25 years of the end of their mission, and at least five defunct spacecraft (that will not deorbit on their own) are actively removed from orbit every year. NASA’s consistent position is that preventing future debris will have greater impact on mitigating orbital debris risks than pursuing development of costly remediation technologies. Although NASA’s compliance rate for end-of-mission disposal within 25 years stands at approximately 96 percent over the last decade, the global compliance rate has only averaged between 20 to 30 percent—much lower than the 90 percent required to slow the rate at which debris is generated in LEO. Despite presidential and congressional directives to NASA over the past decade to develop active debris removal technologies, the Agency has made little to no progress on such efforts. Moreover, debris removal technologies from international agencies and commercial entities are in the early stages of development and testing.

We found that NASA models of the orbital debris environment lack sufficient data, putting the Agency at risk of under- or over-protecting spacecraft from debris. For objects larger than 3 mm, ODPO’s data is limited by the decreasing amount of time available on the three radars it uses to detect and statistically estimate debris due to funding, inoperable equipment, and competing priorities from multiple users. ODPO has also been unsuccessful in securing a source of measurement data on debris 3 mm and smaller in the 400 to 1,000 km range of LEO with failed missions and others canceled due to a lack of funding, a shortcoming particularly concerning because millimeter-sized orbital debris represents the highest penetration risk to most missions operating in LEO. In addition, NASA does not have the ability to track debris smaller than 10 cm in the range of LEO where the International Space Station resides and plans to rely on DOD’s Space Fence to track such debris. However, this ground-based radar system has not yet reached full operational capability, leaving the Station’s critical elements vulnerable to damage from this size debris.

Finally, NASA evaluates ODARs and EOMPs to ensure programs and projects are complying with Agency orbital debris requirements, such as limiting the generation of debris and disposing of spacecraft safely. While the Agency has made improvements to this evaluation process, we found that ODARs and EOMPs were not consistently submitted to the Office of Safety and Mission Assurance in a timely manner (with some submitted nearly a year late), and the process used to route the reports for approval was laborious. Delays in providing the documentation for review could result in a missed opportunity for alternative or low-cost fixes to address mitigation issues.


To better protect spacecraft, maintain the space environment, and address a top Agency risk to obtain direct measurements of millimeter-sized debris, we recommended NASA’s Administrator: (1) lead national and international collaborative efforts to mitigate orbital debris including activities to encourage active debris removal and the timely end-of-mission disposal of spacecraft; (2) collaborate with Congress, other federal agencies, and partners from the private and public sectors to adopt national and international guidelines on active debris removal and strategies for increasing global compliance rates for timely removal of spacecraft at the end of a mission; (3) invest in methods and technologies for removing defunct spacecraft; and (4) prioritize obtaining direct measurements needed to fill the 3 mm and smaller sized debris gap at the 600 to 1,000 km altitude in LEO. In addition, we recommended NASA’s Chief of Safety and Mission Assurance: (5) explore alternative orbital debris radar assets to fill the data gaps caused by the increased costs of utilizing existing radars and the loss of legacy assets; (6) explore commercial alternatives to obtaining information on debris smaller than 10 cm until Space Fence becomes fully operational; and (7) coordinate with Mission Directorate officials to develop and document a formal signature process that clarifies needs and expectations and supports the timely delivery of ODARs and EOMPs prior to key decision point reviews.

We provided a draft of this report to NASA management, who concurred with Recommendations 5 and 7; partially concurred with Recommendations 1, 2, 3, and 4; and non-concurred with Recommendation 6. We consider management’s comments responsive to Recommendations 5 and 7; therefore, those recommendations are resolved and will be closed upon completion and verification of the proposed corrective actions. However, for the remaining recommendations we found the Agency to be unresponsive and therefore those recommendations will remain unresolved pending further discussions with the Agency. Overall, we found management’s responses to these five recommendations lacking in initiative and urgency to lead and collaborate with partners to encourage active debris removal, invest and evaluate methods and technologies for removing defunct spacecraft, prioritize obtaining direct measurements of millimeter-sized debris, and explore alternatives to obtaining information on smaller but potentially dangerous orbital debris.

SpaceRef staff editor.