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[mbs-0021] SO passbands

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调研方向

Start by locating the passband_sampler usage and the behavior established in mbs-s0016. Compare the LAT_passbands_20260126.h5 and SAT_passbands_20260126.h5 group and frequency definitions with the simulated channels; done means LAT and SAT use the selected measured products while LF channels retain simulated per-wafer passbands.

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描述

Context

The map based simulations run the entire simulation for all channels (LAT and SAT, all frequency bands, all wafers). We need to decide which passband products to use.

These are MEASUREMENTS, not simulations: end-to-end passbands (response of the entire optical chain per detector array), measured in-situ on the LAT receiver with an FTS (PIXIE design), with the MLI NDF transmission and FTS frequency shifts corrected. Released as measured by a Rayleigh-Jeans input source with no further correction: nu^2 is NOT divided out, so the curves are directly the power response.

Products by channel (all channels are simulated)

LAT (per-wafer bandpasses, 28 wafer-sub-band curves)

File: LAT_passbands_20260126.h5

One group per wafer and sub-band, each with frequencies + mean_band:

  • f090 / f150: mv13, mv14, mv20, mv24, mv28, mv32, mv34, mv49 (8 wafers, 16 curves)
  • f220 / f280: uv31, uv38, uv39, uv42, uv46, uv47 (6 wafers, 12 curves)

14 wafers total, 28 wafer-sub-band curves (251 points for MF, 201 for UHF).

SAT (per-frequency averaged bandpasses, 4 curves)

File: SAT_passbands_20260126.h5

One averaged band curve per frequency:

  • band_f090 / frequency_f090 (242 points)
  • band_f150 / frequency_f150 (242 points)
  • band_f220 / frequency_f220 (201 points)
  • band_f280 / frequency_f280 (201 points)

Best estimate for SAT passbands, obtained by averaging the LAT data and correcting for the different stop transmissions between the two telescopes (no per-wafer SAT measurements exist yet).

LF channels (30/40 GHz)

No passband product available: LF arrays were measured during the LATR-tester campaigns, but the analysis is explicitly limited to MF and UHF wafers (see memo), so no LF passband curve is released. The LF channels keep using the simulated per-wafer passbands (bandpass_sampler), as done in mbs-s0016.

Notes

  • uv42: no focal plane information for the detectors scanned in 220 and 280 GHz, so no radial correction applied (other wafers had a radial-rescaling correction applied before wafer averaging).
  • The RJ-source measured passbands (nu^2 NOT divided out, i.e. power response) match the convention used when band-integrating sky emission in power units (Jy/sr). The accompanying memo (SO_Bandpass_Calibration_Status_Fall_2025-2.pdf, same wiki page) contains the RJ band centers, bandwidths, and RJ to CMB conversion factors for each measured wafer and sub-band, plus comparisons to simulated and LATR-tester passbands. Total uncertainty is dominated by FTS frequency shift and NDF transmission uncertainties.
  • Selected product: 20260126 (Tommy Alford), the recommended one. A previous version (SAT_passbands.h5 / LAT_passbands.h5) is also on the wiki page. Passbands are stable, no newer product expected in the near term (per the beam/passband team).
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