Abstract
The Photogrammetric Appendage Structural Dynamics Experiment (PASDE) is an International Space Station (ISS) Phase-1 risk mitigation experiment. Phase-1 experiments are performed during docking missions of the U.S. Space Shuttle to the Russian Space Station Mir. The purpose of the experiment is to demonstrate the use of photogrammetric techniques for determination of structural dynamic mode parameters of solar arrays and other spacecraft appendages. Photogrammetric techniques are a low cost alternative to appendage mounted accelerometers for the ISS program. The objective of the first flight of PASDE, on STS-74 in November 1995, was to obtain video images of Mir Kvant-2 solar array response to various structural dynamic excitation events. More than 113 minutes of high quality structural response video data was collected during the mission. The PASDE experiment hardware consisted of three instruments each containing two video cameras, two video tape recorders, a modified video signal time inserter, and associated avionics boxes. The instruments were designed, fabricated, and tested at the NASA Langley Research Center in eight months. The flight hardware was integrated into standard Hitchhiker canisters at the NASA Goddard Space Flight Center and then installed into the Space Shuttle cargo bay in locations selected to achieve good video coverage and photogrammetric geometry.
Highlights
The Photogrammetric Appendage Structural Dynamics Experiment (PASDE)Senior Research Engineer, Structural Dynamics Branch
Has been developed to mitigate technical risk and cost associated with on-orbit measurement of solar array and other flexible appendage structural responses for the International Space Station (ISS) program
The experiment objectives are to demonstrate photogrammetric structural response measurement methods for solar arrays which may be articulating, to provide engineering data on solar array designs similar to those expected to be used on the ISS, and to verify that routine on-orbit spacecraft operational events provide sufficient excitation for structural response testing
Summary
The experiment concept was to use six video cameras at three locations in the Shuttle payload bay to record data on Mir solar array structural response during docked Shuttle/Mir operations, with post-flight data processing to establish measurement feasibility and resolution. From analytical finite element structural models of the coupled (docked) Shuttle/Mir spacecraft, solar array responses to expected on-orbit excitation events were computed These results in conjunction with solid-body viewing models and likely Shuttle payload bay locations led to the PASDE requirement to resolve 0.25 cm (0.1 inch) motions at the expected viewing distances. From the Shuttle/Mir mission plans, a set of on-orbit were identified pre-flight as likely to result in detectable structural motion of the imaged solar array. Structural response to sun track slews was noted at various other times throughout the docked portions of the mission
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