PAPPA: Primordial Anisotropy Polarization Pathfinder Array

The Primordial Anisotropy Polarization Pathfinder Array (PAPPA) is a balloon-based instrument to measure the polarization of the cosmic microwave background and search for the signal from gravity waves excited during an inflationary epoch in the early universe. PAPPA will survey a 20 x 20 deg patch at the North Celestial Pole using 32 pixels in 3 passbands centered at 89, 212, and 302 GHz. Each pixel uses MEMS switches in a superconducting microstrip transmission line to combine the phase modulation techniques used in radio astronomy with the sensitivity of transition-edge superconducting bolometers. Each switched circuit modulates the incident polarization on a single detector, allowing nearly instantaneous characterization of the Stokes I, Q, and U parameters. We describe the instrument design and status.Comment: 12 pages, 9 figures. Proceedings of the Fundamental Physics With CMB workshop, UC Irvine, March 23-25, 2006, to be published in New Astronomy Review

AKARI and BLAST Observations of the Cassiopeia A Supernova Remnant and Surrounding Interstellar Medium

We use new large area far infrared maps ranging from 65 - 500 microns obtained with the AKARI and the Balloon-borne Large Aperture Submillimeter Telescope (BLAST) missions to characterize the dust emission toward the Cassiopeia A supernova remnant (SNR). Using the AKARI high resolution data we find a new "tepid" dust grain population at a temperature of ~35K and with an estimated mass of 0.06 solar masses. This component is confined to the central area of the SNR and may represent newly-formed dust in the unshocked supernova ejecta. While the mass of tepid dust that we measure is insufficient by itself to account for the dust observed at high redshift, it does constitute an additional dust population to contribute to those previously reported. We fit our maps at 65, 90, 140, 250, 350, and 500 microns to obtain maps of the column density and temperature of "cold" dust (near 16 K) distributed throughout the region. The large column density of cold dust associated with clouds seen in molecular emission extends continuously from the surrounding interstellar medium to project on the SNR, where the foreground component of the clouds is also detectable through optical, X-ray, and molecular extinction. At the resolution available here, there is no morphological signature to isolate any cold dust associated only with the SNR from this confusing interstellar emission. Our fit also recovers the previously detected "hot" dust in the remnant, with characteristic temperature 100 K.Comment: Accepted for publication in the Astrophysical Journal. Maps and related data are available at http://blastexperiment.info

The Balloon-borne Large Aperture Submillimeter Telescope: BLAST

The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) is a sub-orbital surveying experiment designed to study the evolutionary history and processes of star formation in local galaxies (including the Milky Way) and galaxies at cosmological distances. The BLAST continuum camera, which consists of 270 detectors distributed between 3 arrays, observes simultaneously in broad-band (30%) spectral-windows at 250, 350, and 500 microns. The optical design is based on a 2m diameter telescope, providing a diffraction-limited resolution of 30" at 250 microns. The gondola pointing system enables raster mapping of arbitrary geometry, with a repeatable positional accuracy of ~30"; post-flight pointing reconstruction to ~5" rms is achieved. The on-board telescope control software permits autonomous execution of a pre-selected 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-hour flight from ESRANGE (Kiruna), Sweden to Victoria Island, northern Canada in June 2005; and a 250-hour, circumpolar-flight from McMurdo Station, Antarctica, in December 2006.Comment: 38 Pages, 11 figures; Replaced with version accepted for publication in the Astrophysical Journal; related results available at http://blastexperiment.info

Nanosatellites for Earth Environmental Monitoring: The MicroMAS Project

The Micro-sized Microwave Atmospheric Satellite (MicroMAS) is a dual-spinning 3U CubeSat equipped with a passive microwave spectrometer that observes nine channels near the 118.75-GHz oxygen absorption line. The focus of this MicroMAS mission (hereafter, MicroMAS-1) is to observe convective thunderstorms, tropical cyclones, and hurricanes from a near-equatorial orbit. The MicroMAS-1 flight unit is currently being developed by MIT Lincoln Laboratory, the MIT Space Systems Laboratory, and the MIT Department of Earth and Planetary Sciences for a 2014 launch to be provided by the NASA CubeSat Launch Initiative program. As a low cost platform, MicroMAS offers the potential to deploy multiple satellites than can provide near-continuous views of severe weather. The existing architecture of few, high-cost platforms, infrequently view the same earth area which can miss rapid changes in the strength and direction of evolving storms thus degrading forecast accuracy. The 3U CubeSat has dimensions of 10 x 10 x 34.05 cm3 and a mass of approximately 4 kg. The payload is housed in the “lower” 1U of the dualspinning 3U CubeSat, and is mechanically rotated approximately once per second as the spacecraft orbits the Earth. The resulting cross-track scanned beam has a FWHM beam width of 2.4º, and has an approximately 20-km diameter footprint at nadir incidence from a nominal altitude of 500 km. Radiometric calibration is carried out using observations of cold space, the Earth\u27s limb, and an internal noise diode that is weakly coupled through the RF front-end electronics. In addition to the dual-spinning CubeSat, a key technology development is the ultra-compact intermediate frequency processor (IFP) module for channelization, detection, and analog-to-digital conversion. The payload antenna system and RF front-end electronics are highly integrated, miniaturized, and optimized for low-power operation. To support the spinning radiometer payload, the structures subsystem incorporates a brushless DC zerocogging motor, an optical encoder and disk, a slip ring, and a motor controller. The attitude determination and control system (ADCS) utilizes reaction wheels, magnetorquers, Earth horizon sensors, peak power tracking, a magnetometer, and a gyroscope. The communications system operates at S-band using the Open System of Agile Ground Stations (OSAGS) with a 2.025—2.120 GHz uplink and 2.200—2.300 GHz downlink at 230 kbps. MicroMAS-1 uses a Pumpkin CubeSat Motherboard with a Microchip PIC24 microcontroller as the flight computer running Pumpkin’s Salvo Real Time Operating System. Thermal management includes monitoring with thermistors, heating, and passive cooling. Power is generated using four double-sided deployable 3U solar panels and one 2U bodymounted panel with UTJ cells and an electrical power system (EPS) with 30 W-hr lithium polymer batteries from Clyde Space. Tests with the MicroMAS-1 Engineering Design Model (EDM) have resulted in modifications to the spinning assembly, stack and ADCS system and have informed the development of the flight model subsystems