The capital, Washington, The conclusion of a NASA report was that reducing the duration of satellites' stays in orbit following the conclusion of their missions is among the most economically viable strategies to tackle the issue of orbital debris.
The report, which was published on May 20 by the Office of Technology, Policy and Strategy of NASA, is a continuation of a report from March 2023 that examined the efficacy of debris remediation methods, or approaches to debris removal. The scope of the revised report was broadened to encompass approaches for debris mitigation, which entails preventing the generation of debris, in addition to monitoring advancements.
One of the most efficacious strategies, as determined by the benefit-to-cost ratio, is the reduction of post-mission disposal time, according to the study. That is the duration required to deorbit a satellite once its mission has been completed. International standards inform U.S. government regulations mandating the deorbiting of satellites within a period of 25 years. In contrast, regulations enacted by the Federal Communications Commission in September of this year shorten the post-mission disposal period to five years.
The NASA study found that even minor reductions of post-mission disposal timeframes offer significant benefits. “We estimated that the benefits of moving to a 15-year rule are 20–750 times the costs and may produce up to $6 billion in net benefits” over 30 years, the report states.
In a scenario where spacecraft are deorbited promptly following the conclusion of their mission, shorter timeframes may provide greater net benefits, of up to $9 billion, despite having lower cost-benefit ratios. In all scenarios considered by the NASA study, reducing post-mission disposal timeframe produces cost-benefit ratios greater than one, indicating that the benefits outweigh the costs.
While the study found enhanced post-mission disposal, a debris mitigation measure, very effective, it also found benefits for some approaches to debris remediation. The most promising is what it termed “just in time” collision avoidance that employs lasers or other technologies to guide large pieces of detritus in peril of colliding with each other.
The cost-benefit ratios of those approaches, the report concluded, are like those for the most promising mitigation approaches, while adding that uncertainties in the models could result in remediation being even more promising. “We encourage the space community to realize that the effectiveness of remediation can be comparable to—and perhaps better than—mitigation and tracking,” the report concluded.
Other promising tools, also based on cost-benefit analyses, include adding some degree of shielding to spacecraft to protect them from impacts as well as enhancing surveillance for “high-risk” conjunctions to enable satellite operators make more informed decisions about collision avoidance maneuvers. However, there are significant uncertainties in those estimates, particularly regarding shielding.
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Other techniques fared surprisingly poorly. Improving spacecraft passivation — removing sources of energy from batteries and propellant tanks that could produce a debris-generating explosion — failed to produce a net positive benefit over 30 years even in the most optimistic scenarios, with the cost of implementing passivation measures outweighing the costs of doing so.
While the study involved significant technical analysis, its results were conveyed in financial metrics. “By measuring everything in dollars, we can directly compare shielding spacecraft to tracking smaller debris or removing 50 large pieces of debris to removing 50,000 smaller ones,” said Jericho Locke, principal author of the report, in a statement.
The new study comes a month after NASA announced a new Space Sustainability Strategy that emphasizes the need to better characterize the orbital debris problem before devising technologies to resolve it. That includes developing a framework for assessing space sustainability and determining what uncertainties are the most critical to resolve.
“This study is part of NASA’s work to rapidly improve our understanding of that environment as outlined in NASA’s recently released Space Sustainability Strategy, by applying an economic lens to this critical issue,” said Charity Weeden, NASA associate administrator the Office of Technology, Policy and Strategy, in a statement.
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