- BOOMERanG experiment
The BOOMERanG experiment (Balloon Observations Of Millimetric Extragalactic Radiation and Geophysics) measured the
cosmic microwave background radiationof a part of the sky during three sub-orbital (high altitude) balloonflights. It was the first experiment to make large, high fidelity images of the CMB temperature anisotropies. By using a telescope which flew at over 42,000 metres high, it was possible to reduce the atmospheric absorption of microwaves to a minimum. This allowed massive cost reduction compared to a satellite probe, though only a small part of the sky could be scanned.
The first was a test flight over
North Americain 1997. In the two subsequent flights in 1998and 2003the balloon was started at the McMurdo Stationin the Antarctic. It used the Polar vortexwinds to circle around the South Pole, returning after two weeks. From this phenomenon the telescope took its name.
The experiment uses
bolometers [cite web | title = Instrumentation of the BOOMERranG experiment | publisher = Ted's Weblog | date = 2002-01-29 | url = http://cmb.phys.cwru.edu/kisner/b2kweblog/hardware.html | accessdate = 2007-04-06] for radiation detection. These bolometers are kept at a temperature of 0.27 kelvin. At this temperature the material has a very low heat capacity according to the Debye law, thus incoming microwave light will cause a strong temperature change, proportional to the intensity of the incoming waves, which is measured with sensitive thermometers.
A 1.2 mirror [cite web | title = Boomerang Instrument | publisher = Caltech Observational Cosmology Group | date = 2003-06-01 | url = http://www.astro.caltech.edu/~lgg/boomerang_instr.htm | accessdate = 2007-04-06] focuses the microwaves onto the focal plane which consist of 16 horns. These horns, operating at 145 GHz, 245 GHz and 345 GHz, are arranged into 8 pixel. So only a tiny fraction of the sky can be seen concurrently so the telescope has to rotate to scan the whole field of view.
Together with experiments like Saskatoon, TOCO, MAXIMA, and others, the BOOMERanG data from 1997 and 1998 determined the angular diameter distance to the surface of last scattering with high precision. When combined with complementary data regarding the value of Hubble's constant, the Boomerang data determined the geometry of the Universe to be flat (see [http://xxx.arxiv.org/abs/astro-ph/9911445] and [http://xxx.arxiv.org/abs/astro-ph/0004404] ) , supporting the
supernovaevidence for the existence of dark energy. The 2003 flight of Boomerang resulted in extremely high signal-to-noise ratio maps of the CMB temperature anisotropy, and a measurement of the polarization of the CMB.
Cosmic microwave background experiments
* [http://boom.caltech.edu Main (Caltech) Site]
* [http://cmb.phys.cwru.edu/boomerang/ Data site]
* [http://stratocat.com.ar/fichas-e/1998/MCM-19981229.htm report on the 1998 flight]
* [http://stratocat.com.ar/fichas-e/2003/MCM-20030121.htm report on the 2003 flight]
* [http://it.arxiv.org/abs/astro-ph/0209132v1 Polarization Sensitive Bolometric Detector]
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