Telecommand/Telemetry Ranging for Deep-Space Applications

Conventional two-way pseudonoise (PN) ranging relies on measuring the time delay between a PN signal transmitted to the spacecraft, and a corresponding synchronized PN signal transmitted from the spacecraft and received on the ground. Recently, we introduced a two-way ranging method ([1]–[3]) which eliminates the need for the downlink PN ranging signal. In this telemetry ranging scheme, the requisite timing measurements are obtained from a data-bearing downlink telemetry signal. In the present paper, we extend the telemetry ranging concept by also eliminating the uplink PN signal, which is replaced by a data-bearing telecommand signal. We describe the architecture and concept of such a system, and describe the fundamental limitations of tracking the timing of uplink telecommand signals when demod-remod correlation techniques are employed via Cramer-Rao bounds. An end-to-end performance analysis shows that in typical scenarios, ranging performance comparable to conventional PN ranging can be achieved.