The recent reentry of the Upper Atmosphere Research Satellite into the Pacific Ocean has focused new attention on the problems created by orbital debris. Posing an occasional threat to Earth, orbital debris, and meteoroids, are a significant problem to NASA’s spacecraft.
A report by the National Research Council reviews NASA’s programs to track orbital debris and meteoroids. A prepublication copy of this 180-page report, “Limiting Future Collision Risk to Spacecraft: An Assessment of NASA’s Meteoroid and Orbital Debris Programs” was released last month). The report was written by the 13-member Committee for the Assessment of NASA’s Orbital Debris Programs, chaired by Donald Kessler. NASA sponsored this project, which was performed under the Aeronautics and Space Engineering Board, Division on Engineering and Physical Sciences, of the National Research Council of the National Academies.
The committee started its work in late 2010, having four meetings with NASA program managers and experts, and individuals from the Office of Science and Technology Policy, the Office of Management and Budget, the European Space Agency, and the Aerospace Corporation. A preface in the report explains that the committee was not charged with assessing the threat that debris and meteoroids presented, or how to remove debris from space. Rather, “the study’s primary task was to review NASA’s current efforts with regard to meteoroids and orbital debris and provide recommendations as to whether NASA should increase or decrease its efforts or pursue new directions.” “In effect, this study is more a review of NASA’s meteoroid and orbital debris programs than an attempt to solve the threat posed by meteoroids and orbital debris,” the report explains.
Early in the report, the committee describes the mounting threat posed by meteoroids and space debris:
“When a handful of reasonable assumptions are used in NASA’s MMOD [meteoroid and orbital debris] models, scenarios are uncovered that conclude that the current orbital debris environment has already reached a ‘tipping point.’ That is, the amount of debris - in terms of the population of large debris objects, as well as overall mass of debris in orbit - currently in orbit has reached a threshold where it will continually collide with itself, further increasing the population of orbital debris. This increase will lead to corresponding increases in spacecraft failures, which will only create more feedback into the system, increasing the debris population growth rate. The increase thus far has been most rapid in low Earth orbit (LEO), with geosynchronous Earth orbits (GEOs) potentially suffering the same fate, but over a much longer time period. The exact timing and pace of this exponential growth are uncertain, but the serious implications of such a scenario require careful attention because of the strategic importance of U.S. space operations.”
The committee found uniform praise for NASA’s Orbital Debris Program and described improvements that have been made at the agency’s Meteoroid Environment Office. To enhance these programs, the committee offered a series of findings and recommendations which have been compiled into seven pages in Chapter 14 of the report. In the concluding section entitled Preparing for the Future, the committee provided the following three findings and two recommendations:
“The long-lived problem of growth in the orbital debris population as a result of debris self-collision and propagation requires that NASA take a long-term perspective to safeguard the space environment for future generations.”
“Although the meteoroid and orbital debris environment may be manageable at present, debris avoidance, mitigation, surveillance, tracking, and response all require money. At present, these costs usually come in the form of additional spacecraft mass and fuel and in the maintenance of debris surveillance systems. Such costs are usually absorbed in the budgets for space mission design, operations, and, in the case of commercial activities, insurance premiums. In the absence of appropriate meteoroid and orbital debris management to deal with the issue, these costs may grow over time. Although they can serve to highlight the importance of NASA’s debris measurement and monitoring activities, at present these costs are not routinely measured and reported.”
“The cost of replacing spacecraft has been used as a measure of the economic harm of a catastrophic debris impact but may underestimate the full cost of harm for two reasons: (1) actual replacement may be difficult because of funding, launch window limitations, or other constraints; and (2) replacement cost, insurance premiums, and other measures of the cost incurred to protect a spacecraft understate the full cost to society as a whole if that spacecraft, damaged by a meteoroid or orbital debris, itself generates debris that then creates potential harm to other spacecraft.”
“NASA should lead public discussion of the space debris problem to emphasize debris as a long-term concern for society that must continue to be addressed today. Necessary steps include improvements in long-term modeling, better measurements, more regular updates of the debris environmental models, and other actions to better characterize the long-term evolution of the debris environment.”
“NASA should join with other agencies to develop and provide more explicit information about the costs of debris avoidance, mitigation, surveillance, and response. These costs should be inventoried and monitored over time to provide critical information for measuring and monitoring the economic impact of the meteoroid and orbital debris problem, signaling when mitigation guidelines may need revision, and helping to evaluate investments in technology for active debris removal.”