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Survey cutouts — ground-based colour context

Design for issue #50 (PyAutoMind prompt ground_based_instruments_optional_noise_psf.md). Ground-based survey imaging for colour context on lenses whose modeling data has no optical counterpart (especially ALMA targets) — explicitly not modeling inputs, which is why the RMS noise map and PSF are optional by design.

The domain decision

DES, SDSS, HSC and their peers deliver pre-reduced coadds through public cutout services. Reducing raw DECam/SDSS frames would be a large new pipeline for products the survey collaborations already made better; so this is a third adapter domain (cutout) beside imaging and visibility: fetch + package, never reduce. The branch mirrors the visibility pattern — its own small pipeline behind the shared registry and the reduce_target domain dispatch.

Phase 1 services (endpoints verified live 2026-07-16, slacs0008 field)

Adapter Service Bands Scale Noise PSF
legacy_surveys legacysurvey.org fits-cutout (DR10) griz (default grz) 0.262" yes — &invvar appends an inverse-variance HDU to the same request no
sdss astroquery.sdss frames + WCS cutout ugriz (default gri) 0.396" no (phase 1) no
panstarrs STScI ps1filenames.py + fitscut.cgi grizy (default gri) 0.25" no (phase 1) no

DES coverage note: the DESI Legacy Imaging Surveys DR10 include the DECam/DES footprint (and far more sky), so legacy_surveys is the DES door — no separate DESDM service integration is needed.

Products per band: <out>/<survey>/<band>/data.fits (native scale, survey WCS), noise_map.fits only where the service ships variance. reduction.json carries a products_optional block stating what was NOT produced and why — a survey cutout must never masquerade as a modeling-ready al.Imaging dataset (no PSF, uncharacterised coadd correlations).

Assessed and deferred / recorded (the "what else is easy" ask)

  • HSC PDR — cutout service is credential-gated (STARs account); deferred until a real need justifies the auth plumbing.
  • unWISE + GALEX — served by the same Legacy viewer endpoint via the layer= parameter (unwise-neo7, galex); the cheapest multi-wavelength extension on the books — IR + UV colour for one small layer dial on the existing fetcher.
  • SDSS/PS1 variance — SDSS frames carry gain/dark-variance/sky metadata and PS1 serves .wt stack files; both are recorded follow-ups if anyone actually needs ground-based noise maps.
  • PSF — Legacy catalogs carry per-brick psfsize_<band>; a Gaussian-FWHM approximate kernel (clearly flagged approximate in provenance) is the recorded follow-up if colour context ever needs even a rough PSF.

Boundaries

  • The branch never imports the imaging stages; the only shared surfaces are the adapter registry, TargetSpec (survey_bands dial, reusing cutout_shape for size), and reduction.json provenance.
  • Unit tests are numpy/astropy-only with fetchers monkeypatched; the real-network demonstration lives in prototypes/survey_cutouts_spike.py.