A Lunar Radar Navigation Concept
NAVAL RESEARCH LAB WASHINGTON DC
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A navigation system concept is described that utilizes the moon as a reflector in a bistatic radar system. By measuring the range and range rate of the receiver relative to the moon, the location of the receiver on the earths surface can be determined in both longitude and latitude. Lunar radar observations have shown that lunar range and range rate measurement accuracies equivalent to or - 30 m can be achieved. By placing a transponder on the moon, the basic measurement accuracy could be improved by a factor of 5. However, for operational measurements where rapid readout is required, these accuracies would probably be degraded by a factor of 5 to 10. Placing three transmitters at appropriate locations on the earths surface will provide worldwide coverage. A transmitter with an average power of 2 MW and a transmitting aperture of 170 m would supply a SN ratio sufficient for reliable position determination with a dipole antenna receiver. One possible radar receiver configuration incorporating both a search and track mode is given. A mathematical analysis of the coverage and the effective position accuracy indicates that 1 worldwide coverage is available 2 time coverage is restricted to 50 percent on the average, but the time distribution of the coverage varies over a monthly period 3 at low latitudes, the effective location accuracy is a function of the moons declination and 4 the optimum accuracy is obtained at high latitudes.
- Space Navigation and Guidance
- Active and Passive Radar Detection and Equipment
- Unmanned Spacecraft