Experiment Definitions for Large and Small Area Surveys

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Decadal Survey Report Reference Design Noise Specifications for large-aperture forecasting

  • To be filled in by Noise Tiger Team

Decadal Survey Report Reference Design Noise Specifications for large-aperture forecasting

  • To be filled in by Noise Tiger Team

Pre-reference-design noise specifications for large-aperture forecasting

Background

The "noise tiger team" convened by the Technical Council is working on a standardized method to go from the reference design to map noise for the large- and small-aperture surveys. While that team is working and the reference design is being finalized, the Science Council chairs asked me (Tom C.) to provide a stopgap set of numbers people can use to start forecasting for the large-area, large-aperture survey. Those numbers are summarized in the email from Gil Holder to the large-area-large-aperture working groups below. Please contact me at tcrawfor_at_kicp.uchicago.edu with any questions.

The Important Part

Hi everyone,

As a starting point for forecasts, for the large aperture wide-field survey let's go with the numbers from the CDT (Table 1 from https://www.nsf.gov/mps/ast/aaac/cmb_s4/report/CMBS4_final_report_NL.pdf). For the small-area (r-focused) survey, things are not quite settled.

That means (via Tom Crawford and Matt Hasselfield):

area of sky: 40% of the full sky
frequencies: 40 90 150 220 270
map depths (T, in units of uK-arcmin): 5.6 1.35 1.81 9.1 17.1
[assumed detector effort in physical det-yrs]: 24268 349455 349455 124251 124251

For beams, baseline would be to assume a diffraction-limited 6m telescope. To be concrete, let's say a 1.4' beam at 150 GHz that then scales as (1/freq).

To include the effects of atmosphere and 1/f, the recommendation is to use the ell scaling at https://cmb-s4.org/CMB-S4workshops/index.php/Update_on_Neff_Forecasts. That means putting in a knee at ell=3400 in TT and at 340 in EE (and presumably BB): NlTT= N0TT(1+ (l /3400)-4.7) NlEE= N0EE(1+ (l /340)-4.7)

It isn't clear to me how these should scale with frequency, though, so it may be ok to go with white noise for the initial go-around