On-orbit repair of satellites using fastener capture plates to eliminate debris

The Hubble Space Telescope (HST) Servicing Mission - 4 (SM-4) presented many unique challenges to the on-orbit crew as well as the engineers responsible for designing the tools and procedures that the crew would utilize during their 5 spacewalks, or Extra-Vehicular Activities (EVAs) For the first time, on-orbit, in-situ repairs of instruments were performed. These repairs replaced electronic boards that were sub-components of the overall instruments. Previous to SM-4, a problem with an instrument dictated that the entire instrument would be swapped with a replacement instrument, at a substantial cost. For the SM-4 mission, there were two different instruments that each required removal and replacement of electronic boards that were contained deep within their structural enclosures. One was the Space Telescope Imaging Spectrometer (STIS) and the other was the Advanced Camera for Surveys (ACS). In order to access these boards for removal and replacement, access panels were carefully removed and captured. In order to remove these panels, it meant first removing 32 (ACS), and 111 (STIS) fasteners of various type (hex, socket-head cap screw, torq-set, etc.) and size ( number 4, 6, 8, etc.). The unique Fastener Capture Plates (FCP) for each instrument repair made it possible for the crew to remove and capture all these fasteners, as well as capturing the access panel, in a safe and controlled manner.