Wide field high cadence CMB survey designs for Chilean telescopes

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 fsky ∼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° 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.