Designs for next generation CMB survey strategies from Chile
  New telescopes are being built to measure the Cosmic Microwave Background
(CMB) with unprecedented sensitivity, including Simons Observatory (SO),
CCAT-prime, the BICEP Array, SPT-3G, and CMB Stage-4. We present observing
strategies for telescopes located in Chile that are informed by the tools used
to develop recent Atacama Cosmology Telescope (ACT) and Polarbear surveys. As
with ACT and Polarbear, these strategies are composed of scans that sweep in
azimuth at constant elevation. We explore observing strategies for both small
(0.42 m) aperture telescopes (SAT) and a large (6 m) aperture telescope (LAT).
We study strategies focused on small sky areas to search for inflationary
gravitational waves as well as strategies spanning roughly half the
low-foreground sky to constrain the effective number of relativistic species
and measure the sum of neutrino masses via the gravitational lensing signal due
to large scale structure. We present these strategies specifically considering
the telescope hardware and science goals of the SO, located at 23 degrees South
latitude, 67.8 degrees West longitude. Observations close to the Sun and the
Moon can introduce additional systematics by applying additional power to the
instrument through telescope sidelobes. Significant side lobe contamination in
the data can occur even at tens of degrees or more from bright sources.
Therefore, we present several strategies that implement Sun and Moon avoidance
constraints into the telescope scheduling. Strategies for resolving conflicts
between simultaneously visible fields are discussed. We focus on maximizing
telescope time spent on science observations. It will also be necessary to
schedule calibration measurements, however that is beyond the scope of this
work. The outputs of this study are algorithms that can generate specific
schedule commands for the Simons Observatory instruments.
