Navigation Demonstrations of Precision Ranging with the Ulysses Spacecraft

Radio tracking data acquired from the Ulysses spacecraft during its flight to Jupiter were used to test experimental navigational techniques for processing highly accurate (1 to 2 m) two-way ranging data. While ranging data with this level of accuracy have been routinely used for navigation of Earth-orbiting spacecraft, ranging data from interplanetary spacecraft have in the past been artificially deweightecl to accuracies of 100 to 1000 m, due to difilculties in mod-eling ground station and transmission media calibration errors and small spacecraft non gravitational forces. This paper describes the incorporation of a simple model of solar plasma-induced variations in ranging data into a procedure for reducing ranging data taken near conjunction with an assumed accuracy near the inherent accuracy of the measurements. Application of this moclel to Ulysses ranging data acquired at either S-band (2.3 GHz) or .X-band (8.4 GHz) frequencies is shown to permit efTective utilization of single-bancl data over S~]n-spa.cecraft separation angles down to 2 degrees.