• How long should screening last? The AFI 91-217 requires launch COLA screening until the objects have entered the space object catalog,5 and this process can take several days. However, due to the large uncertainties in the launch dispersions (deviations from a planned trajectory), the COLA methodology cannot be reasonably used except for a few orbits after launch. This leaves a large gap in time.

• Does one use probability-based screening or miss-distance screening? The probability of collision is a function of the miss distance, the direction of the miss distance relative to the trajectory, and the uncertainty. Thus, one cannot select a probability of collision and obtain a minimum miss distance. The problem with probability-based screening is that the large dispersions with the launch vehicle trajectories usually result in a probability of collision of less than 10–5, and this risk is much lower than other risks usually associated with launch activities. Of 676 conjunctions analyzed by NASA, only 1 percent had probabilities of collisions greater than 10–5. LSP currently uses the probability-based approach.

Finding: The large uncertainties in the launch dispersions (deviations from a planned trajectory) that yield a probability of collision of less than 10–5 translate to a very low return on investment in launch collision avoidance (COLA), and funds could probably be used more effectively in some other area of debris mitigation. However, in the event of a collision during launch, the political realities of potentially having done nothing probably mean that the use of COLA needs to continue, especially for crewed launches.


5 B. Beaver, “Launch Collision Avoidance for MASA ELV Missions,” presentation to the Committee for the Assessment of NASA’s Orbital Debris Programs, January 19, 2011, National Research Council, Washington, D.C.

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