| Summary: | BLAST (The Balloon-borne Large Aperture Submillimeter Telescope) is a 1.9 meter telescope, that feeds a focal plane of 266 feedhorn-coupled bolometers at 250, 350 and 500 microns, with diffraction limited beam FWHM of 30 arcseconds at 250 microns. The experiment has been successfully flown from Sweden in 2005 and from Antarctica in 2006, as described in the poster by M. Truch and collaborators at this meeting. In this poster, we describe the upgrade that will add polarimetric capability to all three wavebands, thereby converting BLAST into BLAST-pol. Polarizing grids will be mounted in front of each of our detector arrays, and a 4 K rotating achromatic half-wave plate will be installed in the optical path, upstream from the cold pupil. BLAST-pol's primary science goal is to create deep, sensitive, large area maps of polarized dust emission in Galactic star forming clouds. For dozens of giant molecular clouds, we will produce three-color polarization maps covering the entire extent of each cloud, with sufficient resolution to probe into the dense cores. These data will provide an unprecedented view of the clouds' magnetic morphologies, the degree of order in the magnetic field, and the relationship to the filamentary structure that is commonly seen in these clouds. BLAST-pol will also measure high latitude polarized dust emission, the understanding of which is crucial for Cosmic Microwave Background Polarization experiments. BLAST-pol is currently under construction with a first flight planned for December 2009 from Antarctica.
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