Design concepts and performance of NASA X-band transponder (DST) for deep space spacecraft applications

The authors summarize the design concepts and measured performance characteristics of an X-breadboard deep space transponder (DST) for future spacecraft applications, with the first use scheduled for the CRAF and Cassini missions (1995 and 1996). The DST consists of a double conversion, superheterodyne, automatic phase tracking receiver, and an X-band exciter to drive redundant downlink power amplifiers. The receiver acquires and coherently phase-tracks the modulated or unmodulated X-band uplink carrier signal. The exciter phase, modulates the X-band downlink signal with composite telemetry and ranging signals. The receiver-measured tracking threshold, automatic gain control, static phase error, and phase jitter characteristics of the breadboard DST are in good agreement with the expected performance. The measured results show a receiver tracking threshold of -158 dBm and a dynamic signal range of 88 dB.<>