The Two Micron All Sky Survey (2MASS): Overview and Status

Abstract

Beginning in early 1997, the Two Micron All Sky Survey (2MASS) project will map the entire sky in the J (1.13–1.37 νm), H (1.50–1.50 μm), and K _s (2.00–2.32 μm) photometric bands to a 3σ limiting sensitivity of 17.1, 16.4 and 15.6 niag, respectively. Often these flux limits are presented as 10σ values (15.8, 15.1, and 14.3 mag, respectively) since this flux level sets the point source completeness (0.99) and reliability (0.9995) regnirernents. The pixel size for the survey is 2.0“. The survey cameras (one for each hemisphere) each contain three NICMOS3 arrays which similtaneously image an 8.5’×8.5’ field in all three survey wavebands. The 1.3 ni survey telescopes scan steadily in declination at a rate of about one arcminute per second while the telescope secondary mirror tilts in the opposite direction to freeze the focal plane position on the sky. Subsequent frames overlap by 84% so that each pixel on the sky is exposed at six dithered positions relative to pixel centers. The frame exposure time is 1.3 seconds.