Differential Tracking Data Types for Accurate and Efficient Mars Planetary Navigation

C. D. Edwards Jr., R. D. Kahn, W. M. Folkner and J. S. Border

Abstract:	Future missions to Mars, embodied in the Space Exploration Initiative, will pose new navigational challenges in terms of requirements on accuracy, efficiency, and reliability. Improved planet-relative tracking during planetary approach will enable aerobraking maneuvers for fuel-efficient orbit insertions. The availability of multiple vehicles in orbit at Mars or on the planet surface offers the potential for high- accuracy, differential observations between vehicles. High- precision differential Earth-based observables can provide improved tracking throughout the range of Mars mission phases including planetary approach, in-orbit navigation, and lander position determination. For example, Differential Very Long Baseline Interferometry (AVLBI) between an approaching spacecraft and a second spacecraft already in orbit at Mars can provide sub-kilometer planet-relative targeting for the approach spacecraft, a key requirement for enabling Mars aerocapture. Once in orbit, both spacecraft can be simultaneously observed in the beamwidth of an Earth antenna, leading to near1 y complete common-mode cancellation of tracking errors. Spacecraft-differenced doppler and range measurements from a single ground antenna, and spacecraft-differenced interferometric observations from two or more Earth-based antennas, can provide lo-meter orbit determination accuracy, and meter- level lander position determination, in all three components of the spacecraft state vectors. Error models for these highly differential data types are discussed, their applications for use in Mars planetary navigation are surveyed, and the benefits and systems requirements involved in implementing and utilizing these observables in the context of an international program of Mars exploration are examined.
Published in:	Proceedings of the 47th Annual Meeting of The Institute of Navigation (1991) June 10 - 12, 1991 Williamsburg Hilton and National Conference Center Williamsburg, VA
Pages:	39 - 46
Cite this article:	Edwards, C. D., Jr., Kahn, R. D., Folkner, W. M., Border, J. S., "Differential Tracking Data Types for Accurate and Efficient Mars Planetary Navigation," Proceedings of the 47th Annual Meeting of The Institute of Navigation (1991), Williamsburg, VA, June 1991, pp. 39-46.
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