The primary goal of the BICEP3 telescope, deployed at the South Pole during the austral summer of 2014-2015, and the upcoming BICEP Array, set to start replacing the Keck Array telescopes this year, is to measure the very faint polarization of the cosmic microwave background (CMB). The CMB is a nearly perfect, uniform black body at 2.7 K, with degree-scale temperature anisotropy of about 0.1 mK and polarization on the order of microkelvin. This radiation was emitted 380,000 years after the Big Bang, at the time of recombination, when the Universe first became transparent to light.

The temperature anisotropy and polarization of the CMB are some of the most powerful ways of understanding the early Universe. Cosmologists believe the Universe experienced a rapid period of cosmic inflation during its first fraction of a second, exponentially expanding from a dense, hot subatomic volume. Many models of inflation predict that this rapid acceleration would have generated gravitational waves that would remain energetic enough 380,000 years later to leave an imprint on the CMB. The BICEP3 and BICEP Array telescopes target this imprint by measuring the pure-curl component of the CMB polarization on degree angular scales. This polarization is largely free of contamination from sources other than primordial gravitational waves.

BICEP2, the precursor to these instruments, detected this B-mode polarization in its three-year data set with a strong significance. However, the joint analysis with Planck satellite data followed and showed that the galactic dust seems to contribute much of the signal. BICEP2 observed at a single frequency band. Multi-frequency observations, first with BICEP3 and Keck Array telescopes, and soon with BICEP3 and BICEP Array telescopes, will help pinpoint the origin of the observed B-mode polarization.

KIPAC is a participant in BICEP series of experiments through the group of Chao-Lin Kuo. Our collaborators include Caltech, JPL, Harvard, Chicago, Minnesota, Berkeley, San Diego, British Columbia, and Toronto.