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TOPIC: ARCADE 2 Instrument

Blobrana

L

Posts: 131433

Date: Jan 7 16:56 2009

ARCADE 2	Permalink

Title: ARCADE 2 Measurement of the Extra-Galactic Sky Temperature at 3-90 GHz Authors: D. J. Fixsen, A. Kogut, S. Levin, M. Limon, P. Lubin, P. Mirel, M. Seiffert, J. Singal, E. Wollack, T. Villela, C. A. Wuensche The ARCADE 2 instrument has measured the absolute temperature of the sky at frequencies 3, 8, 10, 30, and 90 GHz, using an open-aperture cryogenic instrument observing at balloon altitudes with no emissive windows between the beam-forming optics and the sky. An external blackbody calibrator provides an {in situ} reference. Systematic errors were greatly reduced by using differential radiometers and cooling all critical components to physical temperatures approximating the CMB temperature. A linear model is used to compare the output of each radiometer to a set of thermometers on the instrument. Small corrections are made for the residual emission from the flight train, balloon, atmosphere, and foreground Galactic emission. The ARCADE 2 data alone show an extragalactic rise of 50 ±7 mK at 3.3 GHz in addition to a CMB temperature of 2.730 ± .004 K. Combining the ARCADE 2 data with data from the literature shows a background power law spectrum of T=1.26 ± 0.09 [K] (\nu/\nu_0)^{-2.60 ±0.04} from 22 MHz to 10 GHz (\nu_0=1 GHz) in addition to a CMB temperature of 2.725 ±.001 K. Read more (117kb, PDF) __________________

Blobrana

L

Posts: 131433

Date: Jan 6 13:09 2009

ARCADE 2 Instrument	Permalink

Title: The ARCADE 2 Instrument Authors: J. Singal, D.J. Fixsen, A. Kogut, S. Levin, M. Limon, P. Lubin, P. Mirel, M. Seiffert, T. Villela, E. Wollack, C.A. Wuensche The second generation Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission (ARCADE 2) instrument is a balloon-borne experiment to measure the radiometric temperature of the cosmic microwave background and Galactic and extra-Galactic emission at six frequencies from 3 to 90 GHz. ARCADE 2 utilises a double-nulled design where emission from the sky is compared to that from an external cryogenic full-aperture blackbody calibrator by cryogenic switching radiometers containing internal blackbody reference loads. In order to further minimise sources of systematic error, ARCADE 2 features a cold fully open aperture with all radiometrically active components maintained at near 2.7 K without windows or other warm objects, achieved through a novel thermal design. We discuss the design and performance of the ARCADE 2 instrument in its 2005 and 2006 flights. Read more (2953kb, PDF) __________________

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