Designs for next generation CMB survey strategies from Chile

Jason R. Stevens, Neil Goeckner-Wald, Reijo Keskitalo, Nialh McCallum, Aamir Ali, Julian Borrill, Michael L. Brown, Yuji Chinone, Patricio A. Gallardo, Akito Kusaka, Adrian T. Lee, Jeff McMahon, Michael D. Niemack, Lyman Page, Giuseppe Puglisi, Maria Salatino, Suet Ying D. Mak, Grant Teply, Daniel B. Thomas, Eve M. VavagiakisEdward J. Wollack, Zhilei Xu, Ningfeng Zhu

Research output: Chapter in Book/Report/Conference proceedingConference contribution

13 Scopus citations


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° South latitude, 67.8° 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. Scan strategies can also be a powerful tool to diagnose and mitigate instrumental systematics either by using multiple scans to average down systematics or by providing null tests to diagnose problems. We discuss methods for quantifying the ability of an observation strategy to achieve this. 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.

Original languageEnglish (US)
Title of host publicationMillimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX
EditorsJonas Zmuidzinas, Jian-Rong Gao
ISBN (Print)9781510619692
StatePublished - 2018
Externally publishedYes
EventMillimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX 2018 - Austin, United States
Duration: Jun 12 2018Jun 15 2018

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


OtherMillimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX 2018
Country/TerritoryUnited States

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


  • Cosmic Microwave Background
  • Observing Strategy
  • Simons Observatory


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