The Simons Observatory: A fully remote controlled calibration system with a sparse wire grid for cosmic microwave background telescopes

Abstract

For cosmic microwave background (CMB) polarization observations, calibration of detector polarization angles is essential. We have developed a fully remote controlled calibration system with a sparse wire grid that reflects linearly polarized light along the wire direction. The new feature is a remote-controlled system for regular calibration, which has not been possible in sparse wire grid calibrators in past experiments. The remote control can be achieved by two electric linear actuators that load or unload the sparse wire grid into a position centered on the optical axis of a telescope between the calibration time and CMB observation. Furthermore, the sparse wire grid can be rotated by a motor. A rotary encoder and a gravity sensor are installed on the sparse wire grid to monitor the wire direction. They allow us to achieve detector angle calibration with expected systematic error of $0.08^{\circ }$. The calibration system will be installed in small-aperture telescopes at Simons Observatory.

References in corpus (6)

• Self-Calibration of CMB Polarization Experiments
• CMB polarimetry with BICEP: instrument characterization, calibration, and performance
• Characterising cosmic birefringence in the presence of galactic foregrounds and instrumental systematic effects
• Signals of Axion Like Dark Matter in Time Dependent Polarization of Light
• Simons Observatory Small Aperture Telescope overview
• Photon noise correlations in millimeter-wave telescopes

Cited by in corpus (5)

• Modeling parity-violating spectra in Galactic dust polarization with filaments and its applications to cosmic birefringence searches
• Tomographic constraint on anisotropic cosmic birefringence
• The Simons Observatory: A Minimum-Cost Matching Algorithm for Pairing Measured Resonances with Designed Detectors
• The Simons Observatory: Design, Integration, and Current Status of Small Aperture Telescopes
• QUIJOTE-TFGI polarization calibration -- Ground characterization and on-sky validation with Tau A and the Moon