Michael Armatys of Collins Aerospace

Renewed interests in landing and working on the Moon again are now also expected to exploit the latest technologies in Networked Communications and Positioning, Navigation and Timing (PNT) capabilities to support operations on or near the Lunar surface. To provide accurate PNT capabilities, one promising option is to utilize the Global Navigation Satellite System (GNSS) infrastructures that already exist in Earth orbit if one were able to overcome the two principal challenges associated with it: weak signals and poor geometry, when observed by users on the Moon.

Experiments have shown that even though GNSS signals are optimized for operational spaces near the surface of the Earth, spacecraft traveling even beyond geosynchronous orbits can receive weakened GNSS signals, based on a variety of proven GNSS methods already available to track signals that are stressed in military environments. Recent results obtained by an experimental payload on a commercial lunar lander have shown the feasibility of tracking such weak signals even as far out as the Moon.

On and near the Moon’s surface however, all the visible Earth-orbiting GNSS signals appear to be arriving from rather similar directions (approx. 8° max. angular spread). Because of poor geometry, standard GNSS positioning using pseudoranges (based on time delay from separation range and receiver clock error) has a characteristic that is vulnerable to incurring a substantial amount of positioning error in the longitudinal direction between the receiving observer and the GNSS satellites.

This presentation will describe a means to address the problem from poor satellite geometry that uses two-way-timing (TWT) and a local Moon-based reference station for a receiver clock-aiding concept. It first introduced by engineers at Rockwell Collins in 2005 for Differential GPS applications to improve solution accuracy. The idea was called Communication-linked Time Transfer Augmentation for Geometry Enhancement, or CoTTAGE. This technique can result in positioning accuracy performance at the 10-meter level on the Moon. Illustration of such performance will show detailed results from first-order analysis. Alternative system configurations and high-level implementation schemes will also be discussed.

Biography:

Dr. Michael Armatys is an Associate Director of Engineering at Collins Aerospace, I.E.E.E. Senior Member and past president of the I.E.E.E. Cedar Rapids Section.  Michael’s work at Collins focuses on new technology development for precision navigation and alternate Positioning, Navigation and Timing (PNT) technologies. Timing technology development includes solutions to share precise time between mobile platforms.

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