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. The horiz on is 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