Estimation of systematic errors in the results of navigational measurements with the use of spacecraft robot onboard facilities

Abstract

The article presents the results of an analytical study of the accuracy of estimating systematic optical errors of onboard navigation measurements that, along with the vector characterizing the motion of the center of mass of the space robot, are included in the vector of the parameters to be specified. The range to the orbital reference point, the relative speed of its motion and the angles between the directions to the orbital landmark and to the navigational stars, one of which is in the plane of the space robots orbit, and the direction to the second one coincides with the normal to this plane are chosen as the primary navigation parameters to be measured by the space robot onboard facilities. The conditions that make it possible to specify the augmented vector of the parameters to be determined are defined. Estimating the systematic errors of measurements we make assumptions about the central gravitational field of the Earth, the normal law of measurement errors with known variances and the constancy of the unknown systematic errors. Analytical expressions of the covariance matrices that make it possible to estimate the maximum achievable accuracy of solving the task depending on the kind of navigational measurements, variances of measurement errors and the number of measurements during a selected measuring interval are obtained. The presented results can be applied to justify the ways of improving the accuracy of the autonomous navigation of a space robot in diagnosing the technical condition of an orbital object.