GEOMAGNETIC NAVIGATION OF NEAR-EARTH SPACECRAFT

A method of determining the motion parameters of the center of mass of near-earth spacecraft (NES) is proposed; this method is based on using both on-board instrumentation as well as a priori geomagnetic field data. Here, certain characteristics of the second information source, which are largely available from geophysics, are periodically refined based on data from on-board geomagnetic as well as extraneous (such as radio) trajectory measurements. Results are given of a simplified version of a full-scale (computer) NES geomagnetic navigation experiment. The simplification consists of a ground-based implementation of the determining component part of the proposed technique, an algorithm for processing on-board geomagnetic measurements (GM); the geomagnetic measurements used came from the Interkosmos-Bulgaria-1300 near-earth spacecraft. Numerical analysis of these measurements was employed to determine the form and find estimates of the prediction error parameters of the globally limited navigational model proposed by the authors for these measurements. A posteriori estimates of the accuracy characteristics of the orbital geomagnetic navigation technique were derived based on GM data on "repeated" trajectory passes (in the sense of sufficient proximity to the geocentric Greenwich longitudes of ascending nodes); these estimates confirm the validity of the technique and its suitability for near-earth spacecraft navigation at low satellite altitudes.