Demonstration of Non-Regenerative Pseudo-Noise Ranging in Parker Solar Probe and DART Missions

Delivery of radiometric data to Earth for tracking and navigation applications is an essential function of the telecommunications subsystem of a spacecraft. For deep space missions, both Doppler and ranging methods are used to determine the spacecraft distance from Earth and trajectory; together they provide a more accurate position estimate. While deep space missions usually use sequential tone ranging, an alternate type of ranging signal called pseudo-noise (PN) ranging can in theory offer increased performance over sequential tones in some conditions. In order to demonstrate in-flight feasibility of using PN ranging with the Frontier Radio deep space radio for the benefit of future missions, four independent tests of this function were conducted at both X-band and Ka-band frequencies for Parker Solar Probe (PSP) mission. Tests were also performed semi-continuously over a course of two weeks for the Double Asteroid Redirection Test (DART) mission using X-band only. Although Frontier Radio has been tested in flight for regenerative PN ranging capabilities, these are the first tests for non-regenerative PN ranging with a newer generation of Frontier Radio. Here described are the results of the demonstrations with respect to navigation data quality, radio frequency link analysis, and lessons learned in ground station operational logistics. Also described is a comparison of sequential tone ranging and PN ranging with consideration for how the theoretical performance compared to observed data; in particular, it was observed that the quality of the navigation data was comparable to that of sequential tone ranging in a low-statistics context. However, PN still has potential advantages in that it may under certain circumstances reduce the total required time to collect data. Future work is required to adequately characterize all the biases in the system, to determine optimal integration times and other configuration parameters, and to decide whether the performance of PN ranging meets the requirements of future missions.