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A Geometric Analysis to Protect Manned Assets from Newly Launched Objects - COLA Gap Analysis
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Author and Affiliation:
Hametz, Mark E.(AI Solutions, Inc., Cocoa Beach, FL, United States);
Beaver, Brian A.(NASA Kennedy Space Center, Cocoa Beach, FL, United States)
Abstract: A safety risk was identified for the International Space Station (ISS) by The Aerospace Corporation following the launch of GPS IIR-20 (March 24, 2009), when the spent upper stage of the launch vehicle unexpectedly crossed inside the ISS notification box shortly after launch. This event highlighted a 56-hour vulnerability period following the end of the launch Collision Avoidance (COLA) process where the ISS would be unable to react to a conjunction with a newly launched object. Current launch COLA processes screen each launched object across the launch window to determine if an object's nominal trajectory is predicted to pass within 200 km of the ISS (or any other manned/mannable object), resulting in a launch time closure. These launch COLA screens are performed from launch through separation plus I 00 minutes. Once the objects are in orbit, they are cataloged and evaluated as part of routine on-orbit conjunction assessment processes. However, as the GPS IIR-20 scenario illustrated, there is a vulnerability period in the time line between the end of launch COLA coverage and the beginning of standard on-orbit COLA assessment activities. The gap between existing launch and on-orbit COLA processes is driven by the time it takes to track and catalog a launched object, identify a conjunction, and plan and execute a collision avoidance maneuver. For the ISS, the total time required to accomplish an of these steps is 56 hours. To protect human lives, NASA/JSC has requested that an US launches take additional steps to protect the ISS during this "COLA gap" period. The uncertainty in the state of a spent upper stage can be quite large after all bums are complete and all remaining propellants are expelled to safe the stage. Simply extending the launch COLA process an additional 56 hours is not a viable option as the 3-sigma position uncertainty will far exceed the 200 km miss-distance criterion. Additionally, performing a probability of collision (Pc) analysis over this period is also not practical due to the limiting effects of these large orbit state uncertainties. An estimated upper bound for Pc for a typical spent upper stage if nominally aligned for a direct broadside collision with the ISS is only on the order of 10-6. For a smaller manned object such as a Soyuz capsule, the risk level decreases to an order of 10'8 . In comparison, the Air Force Range policy (AFI 91-217) for launch COLAs would only eliminate launch opportunities when conjunctions with objects exceed a Pc of 10'5 This paper demonstrates a conservative geometry-based methodology that may be used to determine if launch opportunities pose a threat to the ISS during the COLA gap period. The NASA Launch Services Program at Kennedy Space Center has developed this COLA gap analysis method and employed it fQr three NASA missions to identify potential ISS conjunctions and corresponding launch window closures during the 56-hour at-risk period. In the analysis, for each launch opportunity, the nominal trajectory of the spent upper stage and the orbit state of the ISS are propagated over the 56 hour period. Each time the upper stage crosses the orbit plane of the ISS, the relative radial and argument of latitude separations are calculated. A window cutout is identified if these separation differences fall within a mission-specific violation box, which is determined from the evaluation of a Monte Carlo dispersions analysis that quantifies the potential variation in the upper stage radial and argument of latitude differences. This paper details the results of these analyses and their impacts to each mission.
Publication Date: Jan 01, 2012
Document ID:
20120016669
(Acquired Dec 10, 2012)
Subject Category: SPACE TRANSPORTATION AND SAFETY
Report/Patent Number: KSC-2012-264
Document Type: Conference Paper
Meeting Information: 23rd AAS/AIAA Space Flight Mechanics Meeting; 13-14 Feb. 2013; Kauai,HI; United States
Meeting Sponsor: American Astronautical Society; mUnited States
American Inst. of Aeronautics and Astronautics; United States
Contract/Grant/Task Num: NNK12LA12C
Financial Sponsor: NASA Kennedy Space Center; Cocoa Beach, FL, United States
Organization Source: NASA Kennedy Space Center; Cocoa Beach, FL, United States
Description: 2p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright; Distribution as joint owner in the copyright
NASA Terms: COLLISION AVOIDANCE; INTERNATIONAL SPACE STATION; LAUNCH WINDOWS; LAUNCH VEHICLES; MISSION PLANNING; CAPE KENNEDY LAUNCH COMPLEX; TRAJECTORIES; VULNERABILITY; MONTE CARLO METHOD
Availability Notes: Abstract Only
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