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

Area of Science:

• Cosmology and Astrophysics
• Instrumental Development

Background:

• Accurate calibration of detector polarization angles is crucial for cosmic microwave background (CMB) observations.
• Previous sparse wire grid calibrators lacked remote-controlled capabilities for regular calibration.

Purpose of the Study:

• To develop a fully remote-controlled calibration system for CMB polarization observations.
• To enable regular and automated calibration of detector polarization angles.

Main Methods:

• A sparse wire grid reflects linearly polarized light along the wire direction.
• Two electric linear actuators remotely position the grid on the telescope's optical axis.
• A motor rotates the grid, with a rotary encoder and gravity sensor monitoring wire direction.

Main Results:

• Achieved detector polarization angle calibration with an expected systematic error of 0.08°.
• Developed a novel remote-controlled system for sparse wire grid calibrators.

Conclusions:

• The new system allows for regular, automated calibration, a significant advancement for CMB experiments.
• The system will be implemented in small-aperture telescopes at Simons Observatory, enhancing data quality.