Test Telemetry And Command System (TTACS)

The Jet Propulsion Laboratory has developed a multimission Test Telemetry and Command System (TTACS) which provides a multimission telemetry and command data system in a spacecraft test environment. TTACS reuses, in the spacecraft test environment, components of the same data system used for flight operations; no new software is developed for the spacecraft test environment. Additionally, the TTACS is transportable to any spacecraft test site, including the launch site. The TTACS is currently operational in the Galileo spacecraft testbed; it is also being provided to support the Cassini and Mars Surveyor Program projects. Minimal personnel data system training is required in the transition from pre-launch spacecraft test to post-launch flight operations since test personnel are already familiar with the data system's operation. Additionally, data system components, e.g. data display, can be reused to support spacecraft software development; and the same data system components will again be reused during the spacecraft integration and system test phases. TTACS usage also results in early availability of spacecraft data to data system development and, as a result, early data system development feedback to spacecraft system developers. The TTACS consists of a multimission spacecraft support equipment interface and components of the multimission telemetry and command software adapted for a specific project. The TTACS interfaces to the spacecraft, e.g., Command Data System (CDS), support equipment. The TTACS telemetry interface to the CDS support equipment performs serial (RS-422)-to-ethernet conversion at rates between 1 bps and 1 mbps, telemetry data blocking and header generation, guaranteed data transmission to the telemetry data system, and graphical downlink routing summary and control. The TTACS command interface to the CDS support equipment is nominally a command file transferred in non-real-time via ethernet. The CDS support equipment is responsible for metering the commands to the CDS; additionally for Galileo, TTACS includes a real-time-interface to the CDS support equipment. The TTACS provides the basic functionality of the multimission telemetry and command data system used during flight operations. TTACS telemetry capabilities include frame synchronization, Reed-Solomon decoding, packet extraction and channelization, and data storage/query. Multimission data display capabilities are also available. TTACS command capabilities include command generation verification, and storage.