Polarization calibration using sparse wire grid with the first small aperture telescope (SAT) of Simons Observatory (SO) (Conference Presentation)

Small Aperture Telescopes of Simons Observatory aim to detect the primordial B-mode power spectrum in Cosmic Microwave Background. For the precise measurement of the B-mode, we need to reduce systematic errors from the miscalibration of the polarization angle of transition-edge sensors. We have developed a calibrator using Sparse Wire Grid (SWG). It can calibrate all the detectors at the same time and allows us to extract information on polarization angle, time constant, and polarization efficiency. In this conference, we will present the calibration method and results using SWG.