Method of comparison between determinations of the HIPPARCOS attitude

Abstract

An attitude comparison method for assessing the quality of the attitude estimates obtained by the Hipparcos data reduction consortia (FAST and NDAC) is presented. The method is illustrated by results obtained in a typical FAST-NDAC comparison developed during the attitude determination assessment phase. The aim of the attitude comparison is, initially, to assess the accuracy level of the attitude reconstructions and to point out the main errors and, when possible, their causes, so that the persons responsible for attitude in the consortia can improve their reconstruction methodologies. The second phase of the comparison starts with mass data reduction, when the efficiency of the estimation algorithms and of their software implementations have already been assessed. The tests of the celestial and instrumental reference frame definitions are powerful tools for monitoring many aspects of the data reductions at the same time.