Impact of basic angle variations on the parallax zero point for a scanning astrometric satellite
Context. Determination of absolute parallaxes by means of a scanning astrometric satellite such as Hipparcos or Gaia relies on the short-term stability of the so-called basic angle between the two viewing directions. Uncalibrated variations of the basic angle may produce systematic errors in the computed parallaxes. Aims. We examine the coupling between a global parallax shift and specific variati