Periodic errors of stellar abscissae in the HIPPARCOS experiment caused by oscillations of the basic angle

Abstract

The problem of stellar abscissae error propagation originating from systematic variations of the basic angle during one turn of the Hipparcos satellite is investigated within the framework of a general data processing algorithm. These variations may be caused by systematic irregularities of the heat flux from solar radiation as the satellite's optical unit is enclosed in a hexagonal body. It is shown that oscillations with a period of 60 deg are the most dangerous. A general approach is considered to lessen possible periodic errors by using two different basic angles on board a second-generation astrometric satellite, whose design is under discussion.