DASI: A Degree Angular Scale Interferometer for Imaging
Anisotropy in the Cosmic Microwave Background
N. W. Halverson, J. E. Carlstrom, M. Dragovan,
W. L. Holzapfel, and J. Kovac
7. Ground Shields
Reflective angled ground shields are necessary to prevent the
sidelobes of the interferometer from seeing correlated thermal noise
from the ground and structures surrounding the instrument. The
shields for DASI are shown in Figure 7.
obscured for every element of the array at all angles greater than the
minimum observing angle of 25°. The geometry of the ground
shields is designed to reflect the beam of each of the antennas to the
cold 6 K sky for all angles off boresight £ 90°. Several of
the ground shield panels are hinged and may be lowered to the
horizon to allow observations of planets (always at low elevation at
the South Pole), and calibration with a fixed ground transmitter.
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Last modified Apr 23, 1998