We introduce a Japanese plan for infrared (z-band: 0.9µm) space astrometry (the JASMINE project). It will measure parallaxes, positions with the accuracy of 10 µas and proper motions with the accuracy of 10 µas/year for stars brighter than z ∼ 14 mag. JASMINE can observe about one hundred million stars belonging to the disc and bulge components of our Galaxy, which are hidden by the interstellar dust extinction in optical bands. The number of stars with σ π /π < 0.1 in the direction of the

more »

... tic central bulge is about 10 3 times larger than those observed in optical bands. The main objective of JASMINE is to provide very useful and important astrometric parameters for studying fundamental structures and evolutions of the disc 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 disc far away from us and so it will promote the study of stellar physics. The information from infrared astrometry that JASMINE will provide is very useful also for investigating stars in star formation regions, gravitational lens effects due to disc stars, extra-solar planets, etc. We hope that JASMINE, which is due to be launched in around 2014, can be complementary to Gaia for surveying the bulge and the disc far away from us. Furthermore, we introduce a Nano-JASMINE project which uses a nano-satellite whose size is about 30 cm 3 and whose weight is a few kilograms. 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.