Design and Calibration of the QUIET CMB Polarimeter

QUIET is a large--angular-scale Cosmic Microwave Background (CMB) polarimeter designed to measure the B-mode signal from inflation. The design incorporates a new time-stream ``double-demodulation'' technique, a 1.4-m Mizuguchi--Dragone telescope, natural sky rotation, and frequent boresight rotation to minimize systematic contamination. The levels of contamination in the inflationary signal are below $r=0.1$, the best yet achieved by any B-mode polarimeter. Moreover, QUIET is unique among B-mode polarimeters in using a large focal-plane array of miniaturized High--Electron-Mobility Transistor (HEMT) based coherent detectors. These detectors take advantage of a breakthrough in microwave-circuit packaging to achieve a field sensitivity of $69\,\mu$K$\sqrt{\textrm{s}}$. QUIET has collected $>$ 10,000\,hours of data and recently released results from the first observing season at Q band (43 GHz). Analysis of W-band (95-GHz) data is ongoing. I will describe the Q-band calibration plan which uses a combination of astronomical and artificial sources to convert the raw data into polarization measurements with small and well-understood calibration errors. I will also give a status report on calibration for the upcoming W-band results.