Initial Performance of BICEP3: A Degree Angular Scale 95 GHz Band
  Polarimeter
  BICEP3 is a $550~mm$ aperture telescope with cold, on-axis, refractive optics
designed to observe at the $95~GHz$ band from the South Pole. It is the newest
member of the BICEP/Keck family of inflationary probes specifically designed to
measure the polarization of the cosmic microwave background (CMB) at
degree-angular scales. BICEP3 is designed to house 1280 dual-polarization
pixels, which, when fully-populated, totals to $\sim$9$\times$ the number of
pixels in a single Keck $95~GHz$ receiver, thus further advancing the
BICEP/Keck program's $95~GHz$ mapping speed. BICEP3 was deployed during the
austral summer of 2014-2015 with 9 detector tiles, to be increased to its full
capacity of 20 in the second season. After instrument characterization
measurements were taken, CMB observation commenced in April 2015. Together with
multi-frequency observation data from Planck, BICEP2, and the Keck Array,
BICEP3 is projected to set upper limits on the tensor-to-scalar ratio to $r$
$\lesssim 0.03$ at $95\%$ C.L..
