Observing low elevation sky and the CMB Cold Spot with BICEP3 at the
  South Pole
  BICEP3 is a 520 mm aperture on-axis refracting telescope at the South Pole,
which observes the polarization of the cosmic microwave background (CMB) at 95
GHz to search for the B-mode signal from inflationary gravitational waves. In
addition to this main target, we have developed a low-elevation observation
strategy to extend coverage of the Southern sky at the South Pole, where BICEP3
can quickly achieve degree-scale E-mode measurements over a large area. An
interesting E-mode measurement is probing a potential polarization anomaly
around the CMB Cold Spot. During the austral summer seasons of 2018-19 and
2019-20, BICEP3 observed the sky with a flat mirror to redirect the beams to
various low elevation ranges. The preliminary data analysis shows degree-scale
E-modes measured with high signal-to-noise ratio.
