The Integrated Science Instrument Module (ISIM) Ground Support System (IGSS) Equation Processor (IEP) allows for the general production of “derived” telemetry products in the Raytheon Eclipse ground system used to support the James Webb Space Telescope (JWST) project. The IEP works alongside the Raytheon-provided equation-processing system but provides for support of string data types that the existing equation processing does not support. The string data type production is required to support the manipulation of JWST string telemetry data types, and for the production of string data types to produce readable time conversions from a binary value to year, day, hour, minute, second format that can be directly viewed on real-time telemetry display pages. The user writes equation scripts using the Tool Command Language (TCL) and specifies as part of the definition how the equation is triggered and what the results should look like. The TCL scripting language provides for a fully featured programming language to manipulate the string data in any form imaginable.

The IGSS EP uses the Raytheon Eclipse-provided Application Programming Interface (API) to subscribe to and obtain telemetry data from either the real-time change-only data system, or the all-points processed telemetry system (pts). Two equation processors run simultaneously to support both the real-time and pts data processing systems using the same equation input. Users specify what telemetry data are required to subscribe to and what telemetry triggers equation processing. Users can have the equations output new telemetry data points as well as informational messages to the real-time log. All the processing is performed in real time as the data arrives, and is processed in the Eclipse telemetry systems.

This work was done by Esther Woodward and Jane A. Steck of Goddard Space Flight Center, and Thomas R. Pfarr and Jim Langston of CSC. For further information, contact the Goddard Technology Transfer Office at (301) 286-5810. GSC-16374-1


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This article first appeared in the July, 2015 issue of NASA Tech Briefs Magazine.

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