Telemetry ranging using software-defined radios

Telemetry ranging is a technique that inserts ranging data measured by the spacecraft into the downlink telemetry stream, thereby avoiding the need to allocate downlink power for a ranging signal. This technique has many benefits depending on the mission profile, including increased data return, operational simplification, and spectrum efficiency. The present study considers a variation to the ranging technique presented in [1] in order to facilitate implementation in a software-defined radio (SDR). This implementation tracks an uplink PN range code and measures the code phase coincident with the start of downlink telemetry frames. The phase is then embedded in subsequent telemetry frames. The method is implemented in the JHU/APL Frontier Radio and leverages the PN ranging design from the NASA New Horizons communications system. Initial test results are summarized and indicate that the method is viable for space exploration.