Regenerative Ranging for JPL Software-Defined Radios

Abstract

Communications and navigation are fundamental to robotic spacecraft exploration. NASA spacecraft communicates via radio links with antennas in the deep space network (DSN) located in California, Australia, and Spain. Measurements of range between the DSN and spacecraft are an important and sometimes critical contribution to navigation. For a given pair of uplink and downlink carriers, ranging must generally be accompanied by telemetering, in order to allow for efficient use of spacecraft and ground resources. Regenerative ranging, which is compatible with the simultaneous presence of telemetry, is more efficient in the use of link power than is the current standard (nonregenerative) ranging. This improved efficiency arises because regenerative ranging replaces the wideband filter found in a nonregenerative transponder's ranging channel with a narrowband loop that tracks the range code, so the signal-to-noise ratio in the transponder's ranging channel is large and there is essentially no noise modulated onto the downlink carrier. This paper offers a comparison of pseudonoise (PN) regenerative ranging versus the nonregenerative method of ranging. This paper also describes the implementation of PN regenerative ranging on the Iris transponder, which is a low-power, 0.5U size, DSN-compatible, software-defined radio based on various JPL flight transponder designs. Iris is baselined to be used on 7 out of 13 of the CubeSats flying as secondary payloads on the Space Launch System Exploration Mission-1 launch of the Orion spacecraft.