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5 Collision Avoidance
Pages 36-41

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From page 36...
... The SSN can only warn about collisions with objects identified in their satellite catalog. The current SSN catalog of tracked objects includes essentially all objects larger than 100 cm in diameter in low Earth orbit, and about 95 percent of objects larger than 30 cm in diameter.
From page 37...
... , which stipulates that a maneuver be performed "if the maneuver does not compromise either primary payload or mission objectives." Like all flight rules, this one can be superseded by real-time decisions. ~ , L : ~Show - loc~t~r 1 ~ it: ~ ~ \ i:::: ~ \ ~ ~ 2 x 5 x 2 km maneuver box 5x25x5km alert box FIGURE 5-1 The space shuttle alert and maneuver boxes.
From page 38...
... During that time, nine cataloged objects penetrated the 2 km x 5 km x 2 km box. In five of these nine cases, avoidance maneuvers were not performed because they would have interfered with primary mission objectives.
From page 39...
... Although the Memorandum of Agreement between United States Space Command and Johnson Space Center for Space Control Operations Relationship, Space Shuttle Program Support, and International Space Station Program Support ({JSSPACECOM and JSC, 1996) addresses requirements in a general fashion, it does not state requirements
From page 40...
... Finding. NASA plans to use a new probability-based approach to determine when a collision avoidance maneuver is necessary, but the collision avoidance data currently provided by the SSN is not accurate enough for the new approach to be effective NASA Flight Rules for Collision Avoidance In deciding whether to make a collision avoidance maneuver, NASA flight controllers assess whether the maneuver would compromise primary payload or mission objectives.
From page 41...
... Future shuttle missions that support the ISS will have a limited ability to maneuver. NASA Flight Rule C4.3.2-1, Space Station Translation Maneuvers During Joint Shuttle Operations, states that debris avoidance maneuvers will not be performed during docked operations.

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