The current status of the Nano-JASMINE project

Nano-JASMINE is a nano-size astrometry satellite that will carry out astrometry measurements of nearby bright stars for more than one year. This will enable us to detect annual parallaxes of stars within 300 pc from the Sun. We expect the satellite to be launched as a piggy-back system as early as in 2009 into a Sun synchronized orbit at the altitude between 500 and 800 km. Being equipped with a beam combiner, the satellite has a capability to observe two different fields simultaneously and will be able to carry out HIPPARCOS-type observations along great circles. A 5 cm all aluminum made reflecting telescope with a aluminum beam combiner is developed. Using the on-board CCD controller, experiments with a real star have been executed. A communication band width is insufficient to transfer all imaging data, hence, we developed an onboard data processing system that extracts stellar image data from vast amount of imaging data. A newly developed 2K × 1K fully-depleted CCD will be used for the mission. It will work in the time delayed integration(TDI) mode. The bus system has been designed with special consideration of the following two points. Those are the thermal stabilization of the telescope and the accuracy of the altitude control. The former is essential to achieve high astrometric accuracies, on the order of 1 mas. Therefore relative angle of the beam combiner must be stable within 1 mas. A 3-axes control of the satellite will be realized by using fiber gyro and triaxial reaction wheel system and careful treatment of various disturbing forces.