Astrometry satellites have common technological issues. (A) Astrometry satellites are
required to measure the positions of stars with high accuracy from the huge amount of data
during the observational period. (B) The high stabilization of the thermal environment in
the telescope is required. (C) The attitude-pointing stability of these satellites with
sub-pixel accuracy is also required.
Measurement of the positions of stars from a huge amount of data is the essence of
astrometry. It is needed to exclude the systematic errors adequately for each image of
stars in order to obtain the accurate positions. We have carried out a centroiding
experiment for determining the positions of stars from about 10 000 image data.
The following two points are important issues for the mission system of JASMINE in order
to achieve our aim. For the small-JASMINE, we require the thermal stabilization of the
telescope in order to obtain high astrometric accuracy of about 10 micro-arcsec. In order
to accomplish a measurement of positions of stars with high accuracy, we must make a model
of the distortion of the image on the focal plane with the accuracy of less than 0.1 nm.
We have investigated numerically that the above requirement is achieved if the thermal
variation is within about 1 K / 0.75 h. We also require the accuracy of the
attitude-pointing stability of about 200 mas / 7 s. The utilization of the Tip-tilt mirror
will make it possible to achieve such a stable pointing.