A two-way noncoherent ranging technique for deep space missions

The Johns Hopkins University Applied Physics Laboratory (APL) has adopted an integrated electronics module (IEM) approach for many of its spacecraft programs. As a result APL has developed a relatively simple X-band transceiver that allows the telecommunications subsystem to be manufactured on plug-in cards that fit into the IEM. An issue with the transceiver approach is that the downlink frequency is not related to the uplink frequency. The noncoherent relationship between the uplink and downlink signals has implications in both Doppler tracking and ranging. APL has developed a method for performing highly precise noncoherent Doppler tracking (J.R. Jensen and R.S. Bokulic, IEEE Trans. Aerospace and Electronic Sys., vol. 35, no. 3, pp. 963-973, 1999). This paper addresses a technique for performing accurate ranging with a noncoherent system. Comet Nucleus Tour (CONTOUR) is the first deep space mission to employ a transceiver and rely on the noncoherent ranging technique. Analysis and testing of the technique implemented for the CONTOUR mission is presented. Tests of the noncoherent ranging technique using the CONTOUR communications hardware at the Deep Space Network's (DSN) Development and Test Facility (DTF21) verified that the technique will provide ranging measurements that meet its navigation requirements.