Hubble Space Telescope
(HST) Archive System
NASA Langley Research Center
Hampton, Virginia
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Page Content: William H. Kinard Page Construction: Thomas H. See |
Fuses
Astronaut Hoffman replacing the fuses in
HST berthed in the payload bay.
There are three different fuse-module configurations (four each) in the HST Support system Module (SSM). The P-15 and P-16 fuses were replaced with upgraded versions. Four P-15 Modules (3 and 5 amp fuses) were replaced since one had opened, and the Rate Sensing Units (RSU) fuses were increased in size from three amps to five amps. Four P-16 modules (10 and 20 amp fuses) were replaced since their configuration was questionable. Spare P-17 and Optical Telescope Assembly (OTA) fuses were carried as contingency but were not replaced. The original plugs were returned for ground examination. The fuses were visually inspected and photographically documented before the DC milliohm and high-voltage tests occurred as part of the ground examination procedure. Resistance and current characterization tests were also part of the examination.
A flight spare P-16 module was found to be miswired during ground testing. Two of the four P-16 modules replaced during the servicing mission were miswired. All 20 amp fuses in S/N's 1006 and 1007 were shunted by the twin low-resistance leads such that negligible current could flow through the fuse. Ground test verified open fuse elements in the P-15 Fuse module (S/N 1012). Ground test verified miswiring of two P-16 fuse modules (S/N's 1006 and 1007). No additional discrepancies or degradation of the modules were observed.
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