Reverse-ephemeris navigation uses range and range rate measurement to obtain lunar surface position fixes and navigation using a known ephemeris of an orbiting object or satellite. (Image: NASA)

Scientists at NASA’s Langley Research Center have developed a novel concept for a lunar navigation system based on the reverse-ephemeris technique. Typically, range-related signal measurements from the Earth’s surface are used to locate and track orbital objects (satellites) and establish the ephemeris describing their orbits. For this reverse-ephemeris lunar navigation concept, the process is reversed to give lunar surface position fixes using the known ephemeris of a satellite in lunar orbit.

In conventional GPS navigation systems, the GPS satellite transmits ephemeris data to a receiver on Earth for determining position at the receiver location. For the reverse-ephemeris approach, the receiver becomes the transmitter, and the satellite instead serves more as a fixed reference position with a known ephemeris. This simplifies the satellite requirements and mitigates potential navigational disruptions that can otherwise arise in navigation systems that utilize satellite-based communications, for example, from interference, jamming, etc.

The design consists of lunar surface S-Band (2,400 2,450 MHz) 10 W transceivers ranging with analog translating transponders on a three-satellite constellation in frozen elliptical orbits to provide continuous coverage with service to 300 simultaneous users over 1.8 MHz of bandwidth at the transponder. Digital bases systems are possible too. As compared to GPS-based navigation requiring four or more satellites costing hundreds of millions of dollars, the new NASA concept is based on using only three smallsats.

Only a few inexpensive smallsats are required to implement a lunar navigation system based on this concept. Lunar navigation systems will be needed for future Moon missions, including, for example, for rover navigation, mining operations, exploration, etc. The inventors have conducted analytical simulations to demonstrate the versatility of this innovation when used to support route determination for various autonomous or manned lunar surface operations.

NASA is actively seeking licensees to commercialize this technology. Please contact Licensing Concierge at This email address is being protected from spambots. You need JavaScript enabled to view it. or call at 202-358-7432 to initiate licensing discussions. For more information, visit here .