Computer Science
Scientific paper
Jul 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001hst..prop.8968c&link_type=abstract
HST Proposal ID #8968
Computer Science
Hst Proposal Id #8968
Scientific paper
The Vehicle Disturbance Test {VDT} is used to characterize uncompensated environmental disturbances acting upon the HST during normal operation. The VDT is a passive test {not a forced-response test} used to obtain signatures for both externally induced {e.g. SA-3} and internally induced {e.g. NCC and ACS mechanisms} disturbances for comparison with past VDT results. The disturbances observed will be used as the nominal on-orbit disturbances in pointing control simulations until the next VDT is run. The test occurs after release, and most of the VDT can be run during the BEA period. The -V1 sunpoint portion of the VDT occurs after the BEA period is complete. The VDT shall consist of five separate tests that need not occur consecutively. The overall duration of the VDT tests is at least 17 orbits of spacecraft time including {1} at least 1 full orbit at +V3 sunpoint prior to NCS CPL turn-on while performing ACS mechanism motions simulating routine flight operations, {2} at least 5 full orbits at +V3 sunpoint prior to NCS CPL turn-on, {3} at least 1 full orbit at +V3 sunpoint during NCC startup, {4} at least 5 full orbits at +V3 sunpoint while NCC is operating at steady-state, and {5} at least 5 full orbits at -V1 sunpoint with the NCC operating at steady-state. Each test is initiated via SMS execution of stored program macros in the HST flight computer to switch the attitude control law gains to low-bandwidth maneuver gains, command the gyros into low mode, terminate Velocity aberration and parallax {VAP} processing, and modify flight computer diagnostic mnemonics to display the roll component of DVTHEP. The nominal attitude control law configuration will be restored at the end of each test via SMS execution of stored program macros. The stored program command macros are developed specifically for the VDT by the Flight Software and Pointing Control System groups.
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