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The Next Generation Balloon-borne Large Aperture Submillimeter Telescope (BLAST-TNG) is a submillimeter mapping experiment planned for a 28 day long-duration balloon (LDB) flight from McMurdo Station, Antarctica during the 2018-2019 season. BLAST-TNG will detect submillimeter polarized interstellar dust emission, tracing magnetic fields in galactic molecular clouds. BLAST-TNG will be the first polarimeter with the sensitivity and resolution to probe the similar to 0.1 parsec-scale features that are critical to understanding the origin of structures in the interstellar medium.BLAST-TNG features three detector arrays operating at wavelengths of 250, 350, and 500 mu m (1200, 857, and 600 GHz) comprised of 918, 469, and 272 dual-polarization pixels, respectively. Each pixel is made up of two crossed microwave kinetic inductance detectors (MKIDs). These arrays are cooled to 275 mK in a cryogenic receiver. Each MKID has a different resonant frequency, allowing hundreds of resonators to be read out on a single transmission line. This inherent ability to be frequency-domain multiplexed simplifies the cryogenic readout hardware, but requires careful optical testing to map out the physical location of each resonator on the focal plane. Receiver-level optical testing was carried out using both a cryogenic source mounted to a movable xy-stage with a shutter, and a beam-filling, heated blackbody source able to provide a 10-50 degrees C temperature chop. The focal plane array noise properties, responsivity, polarization efficiency, instrumental polarization were measured. We present the preflight characterization of the BLAST-TNG cryogenic system and array-level optical testing of the MKID detector arrays in the flight receiver.

The Next Generation Balloon-borne Large Aperture Submillimeter Telescope (BLAST-TNG) is a submillimeter mapping experiment planned for a 28 day long-duration balloon (LDB) flight from McMurdo Station, Antarctica during the 2018-2019 season. BLAST-TNG will detect submillimeter polarized interstellar dust emission, tracing magnetic fields in galactic molecular clouds. BLAST-TNG will be the first polarimeter with the sensitivity and resolution to probe the similar to 0.1 parsec-scale features that are critical to understanding the origin of structures in the interstellar medium. With three detector arrays operating at 250, 350, and 500 mu m (1200, 857, and 600 GHz), BLAST-TNG will obtain diffraction-limited resolution at each waveband of 30, 41, and 59 arcseconds respectively.To achieve the submillimeter resolution necessary for its science goals, the BLAST-TNG telescope features a 2.5 m aperture carbon fiber composite primary mirror, one of the largest mirrors flown on a balloon platform. Successful performance of such a large telescope on a balloon-borne platform requires stiff, lightweight optical components and mounting structures. Through a combination of optical metrology and finite element modeling of thermal and mechanical stresses on both the telescope optics and mounting structures, we expect diffraction-limited resolution at all our wavebands. We expect pointing errors due to deformation of the telescope mount to be negligible. We have developed a detailed thermal model of the sun shielding, gondola, and optical components to optimize our observing strategy and increase the stability of the telescope over the flight. We present preflight characterization of the telescope and its platform.

We present here 350 and 500 micron polarization observations of the Lupus I molecular cloud taken during the 2010 BLASTPol Antarctic flight. Lupus I is a nearby, isolated, young, and filamentary molecular cloud making it an ideal target to test magnetically regulated star formation models. In the presence of intermediate to strong magnetic fields (in comparison to turbulence), these models predict the formation of large filaments extended perpendicular to the local magnetic field direction as gas preferentially collapses along the field lines. We compare the BLASTPol polarization observations with previous optical polarimetry and find a uniform large-scale field direction from low to high density in Lupus I, consistent with magnetically regulated star formation models.

We present the thermal model of the Balloon-borne Large-Aperture Submillimeter Telescope for Polarimetry (BLASTPol). This instrument was successfully own in two circumpolar flights from McMurdo, Antarctica in 2010 and 2012. During these two flights, BLASTPol obtained unprecedented information about the magnetic field in molecular clouds through the measurement of the polarized thermal emission of interstellar dust grains. The thermal design of the experiment addresses the stability and control of the payload necessary for this kind of measurement. We describe the thermal modeling of the payload including the sun-shielding strategy. We present the in-flight thermal performance of the instrument and compare the predictions of the model with the temperatures registered during the flight. We describe the difficulties of modeling the thermal behavior of the balloon-borne platform and establish landmarks that can be used in the design of future balloon-borne instruments.

We present here 350 and 500 micron polarization observations of the Lupus I molecular cloud taken during the 2010 BLASTPol Antarctic flight. Lupus I is a nearby, isolated, young, and filamentary molecular cloud making it an ideal target to test magnetically regulated star formation models. In the presence of intermediate to strong magnetic fields (in comparison to turbulence), these models predict the formation of large filaments extended perpendicular to the local magnetic field direction as gas preferentially collapses along the field lines. We compare the BLASTPol polarization observations with previous optical polarimetry and find a uniform large-scale field direction from low to high density in Lupus I, consistent with magnetically regulated star formation models.

We present the second generation BLASTbus electronics. The primary purposes of this system are detector readout, attitude control, and cryogenic housekeeping, for balloon-borne telescopes. Readout of neutron transmutation doped germanium (NTD-Ge) bolometers requires low noise and parallel acquisition of hundreds of analog signals. Controlling a telescope's attitude requires the capability to interface to a wide variety of sensors and motors, and to use them together in a fast, closed loop. To achieve these different goals, the BLASTbus system employs a flexible motherboard-daughterboard architecture. The programmable motherboard features a digital signal processor (DSP) and field-programmable gate array (FPGA), as well as slots for three daughterboards. The daughterboards provide the interface to the outside world, with versions for analog to digital conversion, and optoisolated digital input/output. With the versatility afforded by this design, the BLASTbus also finds uses in cryogenic, thermometry, and power systems. For accurate timing control to tie everything together, the system operates in a fully synchronous manner. BLASTbus electronics have been successfully deployed to the South Pole, and own on stratospheric balloons.

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.

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.