Program Tracks Operation of a Remote Solid-State Recorder

Solid State Recorder Pointer Tracker (SSRPT) is a computer program developed specifically to aid ground-based monitoring and control of two redundant solid-state recorders (SSRs) aboard the Cassini Spacecraft. The SSRs store telemetry data until downlink times, which are limited to a total of about 8 hours per week. With respect to the SSRs, SSRPT serves as an inexpensive substitute for a complete hardware-and-software simulator of the spacecraft. SSRPT makes it possible to track recording- and playback-pointer address positions in the SSR, thereby making it possible to (1) minimize the use of precious uplink and downlink time by commanding the downlinking of only data of interest stored at known addresses and (2) inhibiting recording at addresses from which data are required but have not yet been played back. SSRPT functions in two modes: (1) a calculator mode, in which it performs basic computations where recording and playback bit rates are multiplied by time intervals; and (2) a sequence-predictor mode, in which it predicts pointer positions according to the time line of commands sent to the spacecraft.