Astra: Interdisciplinary study on enhancement of the end-to-end accuracy for spacecraft tracking techniques

• Published in: Acta astronautica 2014-02, Vol.94 (2), p.699-707
• Main Authors: Iess, Luciano, Di Benedetto, Mauro, James, Nick, Mercolino, Mattia, Simone, Lorenzo, Tortora, Paolo
• Format: Article
• Language: English
• Subjects: Solar system exploration; Space navigation; Space telecommunications; Spacecraft tracking systems
• ISSN: 0094-5765; 1879-2030
• DOI: 10.1016/j.actaastro.2013.06.011

Navigation of deep-space probes is accomplished through a variety of different radio observables, namely Doppler, ranging and Delta-Differential One-Way Ranging (Delta-DOR). The particular mix of observations used for navigation mainly depends on the available on-board radio system, the mission phase and orbit determination requirements. The accuracy of current ESA and NASA tracking systems is at level of 0.1mm/s at 60s integration time for Doppler, 1–5m for ranging and 6–15nrad for Delta-DOR measurements in a wide range of operational conditions. The ASTRA study, funded under ESA's General Studies Programme (GSP), addresses the ways to improve the end-to-end accuracy of Doppler, ranging and Delta-DOR systems by roughly a factor of 10. The target accuracies were set to 0.01mm/s at 60s integration time for Doppler, 20cm for ranging and 1nrad for Delta-DOR. The companies and universities that took part in the study were the University of Rome Sapienza, ALMASpace, BAE Systems and Thales Alenia Space Italy. The analysis of an extensive data set of radio-metric observables and dedicated tests of the ground station allowed consolidating the error budget for each measurement technique. The radio-metric data set comprises X/X, X/Ka and Ka/Ka range and Doppler observables from the Cassini and Rosetta missions. It includes also measurements from the Advanced Media Calibration System (AMCS) developed by JPL for the radio science experiments of the Cassini mission. The error budget for the three radio-metric observables was consolidated by comparing the statistical properties of the data set with the expected error models. The analysis confirmed the contribution from some error sources, but revealed also some discrepancies and ultimately led to improved error models. The error budget reassessment provides adequate information for building guidelines and strategies to effectively improve the navigation accuracies of future deep space missions. We report both on updated error budget for radio-metric observables and the system configurations proposed for the upgrade of ESA's tracking and orbit determination systems. •In depth analysis of radio metric observables from the Cassini and Rosetta missions.•Breakdown of leading noise sources on Doppler, ranging and Delta-DOR observables.•Enhancement of ESA tracking systems accuracy by one order of magnitude.•Guidelines for the design of future tracking systems.