General relativistic satellite astrometry

II. Modeling parallax and proper motion

¹ Istituto di Fisica "G. Galilei" , Via Marzolo 1, 35100 Padova, Italy e-mail: fernando.defelice@pd.infn.it; alberto.vecchiato@pd.infn.it
² Osservatorio Astronomico di Torino, Strada Osservatorio 20, 10025 Pino Torinese To, Italy e-mail: bucc@to.astro.it

Corresponding author: M. G. Lattanzi, lattanzi@to.astro

Received: 24 March 2000
Accepted: 22 March 2001

Abstract

The non-perturbative general relativistic approach to global astrometry introduced by de Felice et al. ([CITE]) is here extended to account for the star motions on the Schwarzschild celestial sphere. A new expression of the observables, i.e. angular distances among stars, is provided, which takes into account the effects of parallax and proper motions. This dynamical model is then tested on an end-to-end simulation of the global astrometry mission GAIA. The results confirm the findings of our earlier work, which applied to the case of a static (angular coordinates only) sphere. In particular, measurements of large arcs among stars (each measurement good to ~arcsec, as expected for mag stars) repeated over an observing period comparable to the mission lifetime foreseen for GAIA, can be modeled to yield estimates of positions, parallaxes, and annual proper motions good to ~arcsec. This second round of experiments confirms, within the limitations of the simulation and the assumptions of the current relativistic model, that the space-born global astrometry initiated with Hipparcos can be pushed down to the 10^-5 arcsec accuracy level proposed with the GAIA mission. Finally, the simplified case we have solved can be used as reference for testing the limiting behavior of more realistic models as they become available.