LinCov Analysis of an Automated Celestial Inertial Navigation Approach for GEO Satellites

Abstract

This paper describes a preliminary error analysis of an automated celestial based inertial navigation scheme for a spacecraft located at GEO. The navigation scheme employs line-of- sight measurements to the moon and sun for onboard inertial orbit determination. A linear covariance analysis is used to determine the expected navigation error envelope and to determine the navigation system's sensitivity to potential error sources. Earth-Moon regime of space. 5-6 It is not the intent of this paper to propose a new of novel method for spacecraft navigation, but to study the errors and sensitivities associated with the proposed navigation method. This study proposes the use of line-of-sight vector measurements from the spacecraft to a celestial navigation source, in order to perform onboard orbit determination of a spacecraft located within the GEO belt. The proposed celestial navigation sources are the moon, to be imaged by an onboard optical camera, and the sun, to be viewed by a sun sensor. This study evaluates the performance of the automated celestial based navigation scheme given nominal error inputs to the system. The study also evaluates the sensitivity of the system due to variations in certain parameters. Parameters that are evaluated include sensor and measurement accuracy, attitude pointing errors, and measurement frequency. The performance analysis provides insight into the expected navigation accuracy given choices for other satellite inertial navigation techniques. The analysis is performed using a linear covariance (LinCov) analysis. LinCov allows for a statistical analysis of the potential onboard navigation filter and provides results comparable to those achieved from a Monte Carlo analysis of the onboard navigation filter. 7 This study, while applicable to all bands of space, is evaluating the navigation schemes for a spacecraft at GEO. Results are presented relating the navigation accuracy to both inertial and Earth fixed coordinate frames.