ETC
Calculate SNR for each source JD1, JD2, JD3 individually.
Then stack, adding uncertainties in quadrature.
Sources
HST WFC3/IR F160W fluxes:
JD1 162 nJy
JD2 136 nJy
JD2 42 nJy
z = 11.1
geometry flat, major 0.1", minor 0.1" (a bit conservative; reduces the SNR a bit)
Backgrounds
"Medium" (median) for RA 06:47:55.731, Dec +70:14:35.76 (JD1)
observable roughly Oct. – Mar. with lowest backgrounds in Nov. & Dec.
Dec 1 2022 – lowest
Apr 1 2023 – highest
(JWST launch Oct 31, 2021 + 6 months commissioning = May 2022 science begins hopefully!)
NIRCam Apertures
SW: 0.08" radius aperture (2.5 pixels); 0.6" – 0.99" background annulus
LW: 0.16" radius aperture (2.5 pixels); 0.6" – 0.99" background annulus
as in JDox (but restricting annulus to 1", not 2")
https://jwst-docs.stsci.edu/near-infrared-camera/nircam-predicted-performance/nircam-imaging-sensitivity
NIRSpec
20 groups NRSIRS2 × 5 integrations × 3 dithers (exposures) = 22,102 s
(1473 s / integration is below the recommended 1500 s limit)
PRISM/Clear
3 shutters
Source offset from shutter center: 0.033", 0.098" (0.33, 0.43 fractional shutters)
Average expected given Constrained source centering, which enables targeting of JD1, JD2, JD3 simultaneously
https://docs.google.com/spreadsheets/d/1yUvp_HwH0sTZeEacHXlR7-7QZP-69BZeaxZJK9rVPDA/edit#gid=1319000998
Miscentering will most likely reduce flux 10 – 20% (worse at longer wavelengths)
https://jwst-docs.stsci.edu/near-infrared-spectrograph/nirspec-operations/nirspec-mos-operations/nirspec-mos-operations-slit-losses#NIRSpecMOSOperations-SlitLosses-SlitlossesintheMSAshutterandplanningconstraints
SNR scales roughly as sqrt(t) for exposure time.
SNR scales more roughly as proportional to the line flux. (A 10x stronger line may increase SNR by 8-9x.)
PRISM: dispersion = 25 – 200 Å / pixel (peak at 1.5 µm)
