The Improved Resolution and Image Separation (IRIS) Satellite

Abstract

Natural (such as lunar) occultations have long been used to study sources on small angular scales, while coronographs have been used to study high contrast sources. We propose launching the Improved Resolution and Image Selection (IRIS) Satellite, a large steerable occulting satellite. IRIS will have several advantages over standard occulting bodies. IRIS blocks up to 99.97% of the visible light from the occulted point source. Because the occultation occurs outside both the telescope and the atmosphere, seeing and telescope imperfections do not degrade this performance. If placed in Earth orbit, integration times of 250-2500 \second can be achieved over 95% of the sky, from most major telescope sites. Alternatively, combining IRIS with a basic 2-m (or 4-m) space telescope at the Earth-Sun L2 point could yield longer integration times and simplified orbital dynamics. Applications for IRIS include searching for planets around nearby stars, resolution of micro-lensed LMC and Galactic bulge stars into distinct image pairs, and detailed mapping of solar system planets from the ground. Using ground-based K-band observations, a Jovian planet with a surface temperature of 400 \kelvin or Venus at 700 \kelvin could be imaged at all angular separations greater than about $0.35\as$ out to over $10\parsec$. Space based observations in the K-band (in emission) or B-band (in reflection) could do better. Resolution of microlensed stars would greatly improve our understanding of the Massive Compact Halo Objects (MACHOs) responsible for observed microlensing events and comprising 20-90% of the mass of our galaxy.