An Approach Guidance Method Using a Single Onboard Optical Measurement
An Approach Guidance Method Using a Single Onboard Optical Measurement

Author: Harold A. Hamer

Publisher:

Published: 1970

Total Pages: 92

ISBN-13:

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An empirical method has been developed for onboard guidance within the sphere of influence of a celestial body. For guidance maneuvers made at a relatively large distance from the body, only one preselected measurement from a star to the body is required. Although the method is designed to control the magnitude of the periapsis radius (or entry angle), the periapsis position and velocity automatically remain close to the nominal values. For lunar approach, error analysis with an assumed one-sigma error of 10 seconds of arc in the optical angular measurements and a one-sigma velocity-cutoff error of 0.2 m/sec has shown that perilune radius can be controlled to a one-sigma accuracy of from 7 to 13 km, depending on the time the approach guidance is performed.

Fixed-angle Translunar Guidance Procedures Using Onboard Optical Measurements
Fixed-angle Translunar Guidance Procedures Using Onboard Optical Measurements

Author: Harold A. Hamer

Publisher:

Published: 1971

Total Pages: 50

ISBN-13:

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Onboard procedures requiring only simple calculations have been developed for midcourse and approach guidance for translunar trajectories. For midcourse guidance the procedure relies solely on an optical range measurement. The approach-guidance procedure requires a star-to-body measurement and may require a range measurement, depending on the distance to the moon. For both procedures the velocity-correction vector is applied in a fixed inertial direction. In the approach-guidance procedure either one or two guidance maneuvers are applied, depending on the accuracy desired and tile distance to the moon. An error analysis showed that perilune radius can be controlled to a onesigma accuracy of about 30 km.