Wide Field High Cadence CMB Survey Designs for Chilean Telescopes

TL;DR

This paper introduces innovative wide field, high cadence survey strategies for Chilean CMB telescopes that enhance uniformity and crosslinking, optimizing measurements for major CMB experiments while enabling time-domain astrophysics.

Contribution

The paper proposes novel sinusoidal modulated survey strategies that improve uniformity and crosslinking in wide field CMB observations, addressing limitations of classical azimuthal scans.

Findings

Achieves nearly uniform observation depth across the field.

Significantly improves crosslinking, meeting strict thresholds.

Enables higher cadence observations for time-domain studies.

Abstract

We present new wide field survey strategies for Chilean Large Aperture Telescopes (LAT) measuring the Cosmic Microwave Background (CMB), which we call Sinusoidal Modulated High Cadence Survey Strategies. The strategies were developed during the process of optimizing LAT measurements for the CMB-S4, Simons Observatory, and CCAT-prime collaborations. Observing more than $f_{sky} \sim 0.5$, the telescope consistently achieves high observation efficiency, even with Sun-avoidance enabled. Classical azimuthal scan survey strategies observing fields of equal size suffer from problems of observation depth non-uniformity relative to declination and lack of crosslinking. The new survey strategies described here significantly improve both uniformity and crosslinking while also enabling higher cadence observations for time-domain astrophysics. Uniformity and crosslinking are improved by modulation of azimuthal angular velocity and sinusoidal elevation nods, respectively. In particular, there is nearly uniform observation depth and crosslinking is improved from total lack of crosslinking near -40 degree declination to clearing the strictest thresholds for crosslinking across the entire field. The simulated strategies are compared to the strategies used for the Atacama Cosmology Telescope and previously studied Simons Observatory survey strategies.