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.
This work was done by Edwin P. Kan, Shahen Petrosian, and Barbara Larson of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp under the Software category.
This software is available for commercial licensing. Please contact Don Hart of the California Institute of Technology at (818) 393-3425. Refer to NPO-20423.
This Brief includes a Technical Support Package (TSP).
Program Tracks Operation of a Remote Solid-State Recorder
(reference NPO-20423) is currently available for download from the TSP library.
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Overview
The document outlines the Solid State Recorder Pointer Tracker (SSRPT), a specialized computer program developed for the Cassini spacecraft by a team from Caltech for NASA's Jet Propulsion Laboratory. SSRPT is designed to assist in the ground-based monitoring and control of two redundant solid-state recorders (SSRs) that store telemetry data until downlink times, which are limited to approximately eight hours per week.
SSRPT serves as a cost-effective alternative to a complete hardware-and-software simulator of the spacecraft. Its primary functions include tracking recording and playback pointer address positions in the SSRs, which is crucial for optimizing the use of limited uplink and downlink time. By knowing the addresses of stored data, mission operators can command the downlinking of only the data of interest and inhibit recording at addresses from which data are still required but have not yet been played back.
The program operates in two distinct modes: the "Calculator" mode (ssrptcalc) and the "Sequence Predictor" mode (ssrptsp). In Calculator mode, SSRPT performs basic computations involving delta-time and bit rates, while in Sequence Predictor mode, it predicts pointer positions based on the timeline of commands sent to the spacecraft. This predictive capability allows for efficient management of data and ensures that the SSR does not overwrite important data that has not yet been played back.
The document also highlights the technical aspects of SSRPT, including its implementation in a graphical user interface (GUI) using C language and X-windows with "motif" widgets. It mentions the logical design features of the SSR, particularly in FIFO (First-In-First-Out) mode, where new data recording is inhibited to prevent overwriting unplayed data.
Additionally, the document notes that SSRPT incorporates specific logic from the spacecraft model file (smf) and context variable file (cvf) to enhance its functionality. The work was conducted by Edwin P. Kan, Shahen Petrosian, and Barbara Larson, and the software is available for commercial licensing.
Overall, the SSRPT is a vital tool for mission operations, enabling efficient data management and enhancing the capabilities of the Cassini spacecraft's solid-state recorders.
