BICEP2 III: Instrumental Systematics

Understand

In a companion paper we have reported a $>5\sigma$ detection of degree scale $B $-mode polarization at 150 GHz by the BICEP2 experiment.

• Here we provide a detailed study of potential instrumental systematic contamination to that measurement.
• We focus extensively on spurious polarization that can potentially arise from beam imperfections.
• We present a heuristic classification of beam imperfections according to their symmetries and uniformities, and discuss how resulting contamination adds or cancels in maps that combine observations made at multiple orientations of the telescope about its boresight axis.