Hubble Space Telescope
(HST) Archive System
NASA Langley Research Center
Hampton, Virginia
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Returned Hardware
Solar Array Drive Electronics (SADE)
Background
The SADE interfaces with the Support System Module (SSM) for exchange of operational commands and telemetry data. The SADE operates and controls the Solar Array Drive Mechanisms (SADM) for the orientation of the SAD. It also monitors the position of the arrays and the temperature of the SADM. The SADE interfaces with the SSM for exchange of operational commands and telemetry data. The SADE operates in the following modes: all motors off, one motor on each mechanism operating simulataneously in either direction of rotation (both main or both redundant), one motor on one mechanism in an operating mode as previous, and simultanious operation of both motors in either mechanism.
First Servicing Mission
During the first HST servicing mission the astronauts replaced the Solar Array Drive Electronics (SADE). The astronauts commented that the SADE change out was a challenging EVA. Astronaut Musgrave noted that the D screws were unconnected and floating in the zero-gravity environment inside the SADE unit.
Results of the SADE-1 Post-Retrieval Inspection
Two transistors (T5 and T7) and two diodes (D8 and D10) had been thermally stressed with the conformal coating discolored and charred. Solder on connections became molten and reflowed betweeen the two diodes. Failed transistors gave no indication of defective construction. All 27 Boards were inspected: seven boards were anomalous and two boards were completely replaced. Some modifications were made to SADE-1R, though the returned SADE did not change the modifications required.
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