FOR SPACE-TO-GROUND VOICE, data, and telemetry, both the Space Shuttle and future Crew Exploration Module rely on the constellation of geosynchronous satellites dubbed the Tracking and Data Relay Satellite System (TDRSS). At the heart of the TDRSS satellite architecture is a multiple-access, S-band phased-array antenna. Recently, prototype antenna elements have been produced for the next-generation Tracking and Data Relay Satellite Continuation (TDRS-C) phased-array antenna. This study was performed at the NASA Glenn Research Center (Cleveland, OH) by Carol L. Kory, Kevin M. Lambert, Roberto J. Acosta, and James A. Nessel.

Compared to the multiple-access antenna on the current class of TDRS, the enhanced multiple-access antenna requires elements that achieve greater on-axis gain, simultaneous circular polarization capability, and increased beamwidth. To prove that array elements meeting these demands could be realized, designs that succeeded in simulation were fabricated and tested. They included the following: a helical antenna; a novel short backfire antenna that was excited with a circular waveguide with an integrated polarizer and orthomode transducer (OMT); and a corrugated-horn antenna with an integrated polarizer and OMT. See "Prototype Antenna Elements for the Next-Generation TDRS Enhanced Multiple-Access Array," IEEE Antennas And Propagation Magazine, August 2008, p. 72.