A report describes the NASA Spacecraft Transponding Modem (STM) — a spacecraft transponder now under development for planned use on deep-space missions scheduled for launch in the year 2003. In comparison with a traditional deep-space transponder, the STM will be smaller and less power hungry; the reductions in size and power demand will be effected by use of custom application-specific integrated circuits. The STM will perform all of the traditional deep-space-transponder functions, plus some coding, decoding, and time-tagging functions: The STM will track an X-band uplink signal and transmit both X- and Ka-band downlinks. A command detector, a code-block processor, and hardware command decoder will be integral parts of the STM. Coding functions will include Reed-Solomon coding, convolutional coding, and turbo coding for downlink telemetry. Downlink symbol rates could be ramped linearly to match the expected gain/noise temperature of a receiving station. Data could be transmitted by any of three different phase-modulation schemes at rates from 5 b/s to 24 Mb/s. Other functions will include standard turnaround ranging, regenerative pseudonoise ranging, and differential one-way ranging.

This work was done by Brian Cook, Charles Kyriacou, Constantine Andricos, Gary Burke, James Kowalski, James Layland, Jeff Berner, Jonathan Perret, Narayan Mysoor, Selahattin Kayalar, Amy Holst, Bryan Bell, Vatche Vorperian, and William Whitaker of Caltech for NASA's Jet Propulsion Laboratory. To obtain a copy of the report, "The NASA Spacecraft Transponding Modem," access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp under the Electronics & Computers category.

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Refer to NPO-21004, volume and number of this NASA Tech Briefs issue, and the page number.