Dipartimento di Fisica - Universita' di Roma La Sapienza
B2K: The Payload

B2K is a balloon-borne, multiband bolometric polarimeter for CMB measurements. We fly it from McMurdo, Antarctica,
in a Long Duration Balloon flight launched by NASA-NSBF.

The flight circumnavigates Antarctica at an altitude of about 37 km, approximately along the 78S parallel, during the Antarctic summer.
98 trajectory

Path of the flight of BOOMERanG in 1998. The flight was 11.6 days long, at an average altitude
of 37 km.

In this way we can observe about 4% of the sky, approximately anti-sun and at high galactic latitudes, where foregrounds contamination is minimal.
The payload is reusing most of the original BOOMERanG payload flown in 1998, which successfully measured the power spectrum of the CMB anisotropy. We use the same gondola, off-axis telescope and long duration cryogenic system.

The B2K payload, during integration in McMurdo (Dec.2002)

The telescope of B2K consists of a 1.3m off axis primary at room temperature, and a couple of reimaging mirrors inside the BOOMERanG cryostat.

The spare off-axis mirror used in BOOMERanG. It is 1.3 m in diameter, made of aluminum and polished.


The heart of the cryogenic system is a large 3He refrigerator, cooling all the focal plane at 270 mK for 15 days, and recyclable in flight.

The detectors, 3He fridge and reimaging optics are all contained inside a large dewar with 70 liters of liquid nitrogen and
60 liters of liquid helium.

See also the other BOOMERanG web pages
University of Toronto