A Liaison Navigation Simulation

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Many thousands of simulations have been performed to verify that Liaison Navigation really works. The latest and most realistic simulation is detailed in the slide above. In this simulation, a halo orbiter at L2 tracks a low lunar orbiter in a polar orbit and generates crosslink range measurements. An Extended Kalman Filter is used to process the measurements in simulated real-time. Modeling errors in the orbit determination code simulate inaccurate knowledge of the radiation force models, the lunar gravity field, and the thruster models. The result is a highly accurate simulation that gives the orbit determination accuracy that can be expected in actual operation. In this case, the 1σ position error is 7 m RSS for the low lunar orbiter and 80 m RSS for the halo orbiter. It takes about a day to converge on the correct orbit for the lunar orbiter and 3-6 days for the halo orbiter. After the EKF converges, it can maintain this kind of accuracy indefinitely as long as there are measurements to process.

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