View source for 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

Talk to you all soon,
Gil