Telemetry-based ranging

This paper presents a new two-way, telemetry-based ranging architecture. The scheme uses a conventional uplink ranging signal, but the downlink ranging signal is replaced with an asynchronous telemetry signal whose timing relative to the acquired uplink signal is measured. This measurement, along with the acquired timing of the received telemetry, enables the round-trip light-time to be computed on the ground. Introducing coherency between the uplink carrier frequency and downlink symbol rate makes the system robust to Doppler. Ranging jitter comparable to conventional ranging approaches can be achieved when the downlink data rate is about 15 kbps or higher. At data rates higher than 1 Mbps, more than an order of magnitude improvement in downlink range jitter is possible, although limitations in the ground calibration process may make these gains difficult to realize. Advantages of the system include the ability to simultaneously collect ranging measurements and transmit the highest supported telemetry rate throughout a pass, and compatibility with suppressed carrier signaling and higher order modulations. This can result in significant additional ranging data and. total data volume return.