BICEP2 and Keck Array operational overview and status of observations
  The BICEP2 and Keck Array experiments are designed to measure the
polarization of the cosmic microwave background (CMB) on angular scales of 2-4
degrees (l=50-100). This is the region in which the B-mode signal, a signature
prediction of cosmic inflation, is expected to peak. BICEP2 was deployed to the
South Pole at the end of 2009 and is in the middle of its third year of
observing with 500 polarization-sensitive detectors at 150 GHz. The Keck Array
was deployed to the South Pole at the end of 2010, initially with three
receivers--each similar to BICEP2. An additional two receivers have been added
during the 2011-12 summer. We give an overview of the two experiments, report
on substantial gains in the sensitivity of the two experiments after
post-deployment optimization, and show preliminary maps of CMB polarization
from BICEP2.
