The Balloon-borne Large Aperture Submillimeter Telescope: BLAST

The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) is a suborbital surveying experiment designed to study the evolutionary history and processes of star formation in local galaxies (including the MilkyWay) and galaxies at cosmological distances. The BLAST continuum camera, which consists of 270 detectors distributed between three arrays, observes simultaneously in broadband (30%) spectral windows at 250, 350, and 500 mu m. The optical design is based on a 2 m diameter telescope, providing a diffraction-limited resolution of 3000 at 250 mu m. The gondola pointing system enables raster mapping of arbitrary geometry, with a repeatable positional accuracy of similar to 30''; postflight pointing reconstruction to less than or similar to 5'' rms is achieved. The onboard telescope control software permits autonomous execution of a preselected set of maps, with the option of manual override. In this paper we describe the primary characteristics and measured in-flight performance of BLAST. BLAST performed a test flight in 2003 and has since made two scientifically productive long-duration balloon flights: a 100 hr flight from ESRANGE (Kiruna), Sweden to Victoria Island, northern Canada in 2005 June; and a 250 hr, circumpolar flight from McMurdo Station, Antarctica, in 2006 December.