A weak-signal GPS architecture for lunar navigation and communication systems

As envisioned by a broad series of trade studies, the lunar elements of the NASA Exploration Initiative will require a significant increase in navigation and communication capacity [1]. Exploration combines robotic and human mission elements that should ideally support each other in terms of advancing the ability to discover, operate, and support a sustained human presence in the lunar environment. While a small set of individual sorties may be able to incur the inefficiencies of developing mission-specific navigation and communication capability, or relying on current systems, realizing the fundamental goal a sustained human presence will greatly strain current systems. In conjunction with a small spacecraft-based lunar navigation and communication system solution jointly among JHU/APL, NASA/GSFC, NASA/GRC and JPL, JHU/APL analyzed the incorporation of a Global Positioning System component to an infrastructure of spacecraft designed to provide communication and navigation service to lunar assets. This research is described, included the technology basis for reception of GPS in the lunar environment, the impact on the space, ground, and user segments of a lunar navigation and communication infrastructure, and the benefits and costs of such an architectural implementation. Specific technologies include leveraging JHU/APL weak-signal GPS processing and the use of disciplined ultra-stable oscillators.