BLAST-pol: Balloon-borne Large Aperture Submillimeter Telescope for Polarimetery

BLAST-pol (Balloon-borne Large Aperture Submillimeter Telescope for Polarimetery) combines a 1.9 meter Cassegrain telescope and a submillimeter polarimeter that operates in three bands (250, 350, and 500 microns), each with 30% bandwidth. The detection system is comprised of 270 silicon-nitride micromesh bolometers distributed on three focal plane arrays with 30", 42", and 60" FWHM beam sizes, respectively. The detectors are a prototype for the SPIRE instrument used on Herschel. Polarization sensitivity is achieved by placing polarized grids on the bolometer arrays and with a rotatable Achromatic Half Wave Plate (AHWP) located in front of the arrays. The instrument operates on a balloon at an altitude of ~40km due to the high opacity of the earth’s sea level atmosphere at submillimeter wavelengths. The main scientific objective of BLAST-pol is to determine what role magnetic fields play in star formation. This is achieved by making large, high resolution, linear polarization maps of giant molecular clouds (GMCs), and their substructures. These maps can then be compared to maps created using numerical turbulence simulations to ascertain how magnetic fields affect the morphology and lifetime of these structures. The non-polarized version of BLAST has had two scientific flights and is scheduled to fly again as BLAST-pol in December 2010 from McMurdo, Antarctica.