Accession Number:

ADA275249

Title:

Lunar Gravitational Field Estimation and the Effects of Mismodeling Upon Lunar Satellite Orbit Prediction

Descriptive Note:

Master's thesis

Corporate Author:

CHARLES STARK DRAPER LAB INC CAMBRIDGE MA

Personal Author(s):

Report Date:

1993-06-01

Pagination or Media Count:

174.0

Abstract:

Lunar spherical harmonic gravity coefficients are estimated from simulated observations of a near-circular low altitude polar orbiter disturbed by lunar mascons. Lunar gravity sensing missions using earth-based near-side observations with and without satellite-based far-side observations are simulated and least squares maximum likelihood estimates are developed for spherical harmonic expansion fit models. Simulations and parameter estimations are performed by a modified version of the Smithsonian Astrophysical Observatorys Planetary Ephemeris Program. Two different lunar spacecraft mission phases are simulated to evaluate the estimated fit models. Results for predicting state covariances one orbit ahead are presented along with the state errors resulting from the mismodeled gravity field. The position errors from planning a lunar landing maneuver with a mismodeled gravity field are also presented. These simulations clearly demonstrate the need to include observations of satellite motion over the far side in estimating the lunar gravity field. The simulations also illustrate that the eighth degree and order expansions used in the simulated fits were unable to adequately model lunar mascons.

Subject Categories:

  • Astronomy
  • Astronautics
  • Spacecraft Trajectories and Reentry

Distribution Statement:

APPROVED FOR PUBLIC RELEASE