JASMINE: Japan Astrometry Satellite Mission for INfrared Exploration

Abstract

We introduce a Japanese plan for infrared (z-band: 0.9 $\mu$m) space astrometry (the JASMINE-project). It will measure parallaxes, positions with the accuracy of 10 $\mu$as and proper motions with the accuracy of 10 $\mu$as/yr for stars brighter than z$\sim$14. JASMINE can observe about $10^8$ stars belonging to the disk and bulge components of our Galaxy which are hidden by interstellar dust extinction in optical bands. The number of stars with $\sigma_{\pi}/\pi<0.1$ in the direction of the Galactic central bulge is about $10^3$ times larger than those observed in optical bands, where $\pi$ is a parallax and $\sigma_{\pi}$ is an error of the parallax. The main objective of JASMINE is to provide very useful and important astrometric parameters for studying fundamental structures and evolution of the disk and bulge components of the Milky Way Galaxy. Furthermore, the astrometric parameters given by JASMINE will give us exact absolute luminosities and motions of many stars in the bulge and the disk far away from us, so it will promote the study of stellar physics. The information of infrared astrometry that JASMINE will provide is very useful also for investigating stars in star formation regions, gravitational lens effects due to disk stars, extra-solar planets, etc. JASMINE will be launched around 2014 and a candidate for the orbit is a Lissajous orbit around the Sun-Earth L2 point with about a 5-yr mission life. We adopt a 3-mirror optical system (modified Korsch system) with a primary mirror of $\sim$1.5-m diameter in an instrument design of JASMINE. A beam combiner should be used for performance of the global astrometry as used in the Hipparcos satellite. On the astro-focal plane, we put about 100 new-type CCDs for the z-band in which TDI mode (drift scan mode) can be operated. The effective field of view is 0.23 square degrees. The consideration of overall system (bus) design is now going on in cooperation with the Japan Aerospace Exploration Agency (JAXA). Furthermore, we introduce the Nano-JASMINE project which uses a nano-satellite with a size of about 20 cm³ and a weight of a few kg. The objective of Nano-JASMINE is verification of the observing strategy adopted in JASMINE and examination of some important technical issues for the JASMINE project. It will be launched around 2006.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html