AN EXPLORATORY STATISTICAL ANALYSIS OF A PLANETnAPPROACH-PHASE GUIDANCE SCHEME USING ANGULARnMEASUREMENTS WITH SIGNIFICANT ERROR

摘要

An exploratory analysis of vehicle guidance during the approach to a target planet is presented. The objective of the guidance maneuver is to guide the vehicle to a specific perigee distance with a high degree of accuracy and minimum corrective velocity expenditure. The guidance maneuver is simulated by considering the random sampling of real measure-ments with significant error and reducing this information to prescribe appropriate corrective action. The instrumentation system assumed in-cludes optical and/or infrared devices to indicate range and a reference angle in the trajectory plane. Statistical results are obtained by Monte-Carlo techniques and are shown as the expectation of guidance accuracy and velocity-increment requirements. Results are nondimensional and applicable to any planet within limits of two-body assumptions.nThe problem of determining how many corrections to make and when to make them is a consequence of the conflicting requirement of accurate trajectory determination and propulsion. Optimum values were found for a vehicle approaching a planet along a parabolic trajectory with an initial perigee distance of 5 radii and a target perigee of 1.02 radii. In this example measurement errors were less than 1 minute of arc. Re¬sults indicate that four corrections applied in the vicinity of 50, 16, 5, and 1.5 radii, respectively, yield minimum velocity-increment require¬ments. Thrust devices capable of producing a large variation of velocity-increment size are required. For a vehicle approaching the earth, miss distances within 32 miles are obtained with 90-percent probability. Total velocity increments used in guidance are less than 3300 feet per second with 90-percent probability. It is noted that the above representative results are valid only for the particular guidance scheme hypothesized in this analysis.