Hubble’s Science Instrument Command and Data Handling Module
Hubble's Science Instrument Command and Data Handling Module (SI C&DH) works with Hubble's data management Unit (DMU) to process, format, and temporarily store information on Hubble's digital recorders or transmit science and engineering data to the ground. The SI C&DH is a collection of fourteen components, arranged in six stacks that are mounted on a tray to create a single Orbital Replacement Unit (ORU). This tray is mounted to the inside of the System Support Module's Bay 10 door. These components work together to perform two basic functions: controlling Hubble's scientific instruments and formatting and storing the instruments' scientific and engineering data. There are 4 key-way bolts that position the tray onto the door and 6 captive bolts that secure the tray to the door. All 10 bolts have the Hubble "standard" 7/16-inch hex-head interface. There are no hand-mated electrical connectors on the SI C&DH tray. Instead, a bolt is turned to operate a "blind mate" interface that makes the electrical connections to the Hubble spacecraft. As far as ORUs go, the SI C&DH is relatively easy to get to and replace.