AKARI—Infrared Satellite Mission—Present Status and Early Results

Abstract

AKARI, formerly known as ASTRO-F, is a satellite mission dedicated to infrared astronomy for the first time in Japan. It has a 685-mm aperture telescope with two focal-plane instruments cooled by liquid helium (LHe) and mechanical coolers on board for observations in the 2–180 μm infrared spectral range. AKARI was launched on 2006 February 21 (UT) into a sun-synchronous polar orbit and started observations in May, 2006. It carried 179 liter LHe that lasted for 550 days and observations with LHe were carried out for more than 15 months. During the LHe holding period, AKARI made all-sky survey observations with six bands from 9 to 160 μm, which surpass the IRAS all-sky survey data in the sensitivity, spatial resolution, and spectral coverage. Together with the all-sky observation, AKARI also made pointing observations for about 10 min at a given position of the sky to execute deep imaging and spectroscopy from near- to far-infrared. Both focal-plane instruments work successfully on orbit and more than 90% of the sky was observed in the all-sky survey. After LHe exhaustion, near-infrared observations are planned to continue. This paper reports the in-orbit performance of AKARI and its early observational results so far obtained.