Experiment Definitions for Large and Small Area Surveys
"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"
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
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|
|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