CARA Science: Viper
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Viper, a 2.1 meter off-axis telescope optimized for
was installed at the South Pole in January 1998. The optical design of
Viper includes an electrically driven mirror which allows the Viper
beam to be rapidly swept across the sky. The Viper beam sweeps
several degrees without significant beam distortion and without large
variation of telescope emission or ground emission pick-up. This
large sweep ability, along with the exceptional stability of the South
Pole atmosphere allow Viper to be used for observations that extend
across several degrees.
During 2000 Viper will host a CMB polarization experiment.
Observations of CMB polarization have the
potential to reveal the initial source of the anisotropies
created within the
first fraction of a second of the universe. So far there
is no detection of polarization of the CMB, but predictions
of the polarization fraction are 1 to 10% polarization.
If these levels are correct, then the instrument
being built for Viper may have sufficient sensitivity to make a
The ACBAR bolometer array will be deployed on
Viper in November 2000 to extend
Viper's CMB anisotropy and SZE observations to higher
frequencies and smaller angular scales. The
Viper telescope will also be used to make sensitive
polarization observations with the SPARO
bolometer array for
the remainder of 1999, and for extended periods in future years.
Viper is the first CMB telescope designed to observe through
the Antarctic winter; it is about to finish its second successful
winter of observing. Its major accomplishments to date are:
- Constraints on the anistropy of the CMB over the range
180 < l < 600, across the
critical first acoustic peak in the anisotopy power spectrum. The
data from the first year, shown in
received considerable attention as they indicated the presence of
the first acoustic peak at a location consistent with a flat universe.
Data from the second year may provide a factor of ten
more sky coverage and thereby a factor of three lower uncertainties.
- Detection of the Sunyaev-Zel'dovich effect (SZE) toward the
nearby galaxy culuster Abell~3667 -- see
For more information
The group has a website at
Viper is based at Carnegie-Mellon University.
For more information, contact Jeff Peterson,