Project: datamanagement
Issue DM-6529: Investigate single frame processing astrometry failures/poor solutions on some HSC chip/visits.
The astrometric solution of some visit/ccd combinations for HSC data are failing or finding very poor solutions. This typically occurs for the outermost (highly fringed) ccds (e.g. 100..103, 95). I provide some sample output below. {code:title=LSST bad fit: visit=19696 ccd=100} processCcd.calibrate.astrometry.refObjLoader: Loaded 71 reference objects processCcd.calibrate.astrometry.matcher: filterStars purged 0 reference stars, leaving 71 stars processCcd.calibrate.astrometry.matcher: Purged 4436 unusable sources, leaving 288 usable sources processCcd.calibrate.astrometry.matcher: Matched 6 sources processCcd.calibrate.astrometry.matcher WARNING: Number of matches is smaller than request processCcd.calibrate.astrometry: Matched and fit WCS in 1 iterations; found 6 matches with scatter = 0.000 +- 0.000 arcsec {code} {code:title=HSC fit: visit=19696 ccd=100} 2016-06-10T17:13:54: processCcd.calibrate.astrometry: Found 80 catalog sources 2016-06-10T17:13:54: processCcd.calibrate.astrometry: Matching to 119/148 good input sources 2016-06-10T17:13:55: processCcd.calibrate.astrometry: Matched 20 sources 2016-06-10T17:13:55: processCcd.calibrate.astrometry WARNING: Number of matches is smaller than request 2016-06-10T17:13:55: processCcd.calibrate.astrometry: 20 astrometric matches for 100, 0_31 2016-06-10T17:13:55: processCcd.calibrate.astrometry: Refitting WCS 2016-06-10T17:13:55: processCcd.calibrate.astrometry: Astrometric scatter: 0.038076 arcsec (with non-linear terms, 20 matches, 0 rejected) {code} {code:title=LSST failed fit: visit=19696 ccd=103} processCcd.calibrate.astrometry.refObjLoader: Loaded 68 reference objects processCcd.calibrate.astrometry.matcher: filterStars purged 0 reference stars, leaving 68 stars processCcd.calibrate.astrometry.matcher: Purged 2206 unusable sources, leaving 225 usable sources processCcd.calibrate.astrometry.matcher: Matched 4 sources processCcd.calibrate.astrometry.matcher WARNING: Number of matches is smaller than request processCcd FATAL: Failed on dataId={'taiObs': '2015-01-21', 'pointing': 1116, 'visit': 19696, 'dateObs': '2015-01-21', 'filter': 'HSC-I', 'field': 'SSP_UDEEP_COSMOS', 'ccd': 103, 'expTime': 300.0}: File "src/sip/CreateWcsWithSip.cc", line 142, in lsst::meas::astrom::sip::CreateWcsWithSip::CreateWcsWithSip(const std::vector<_RealType>&, const lsst::afw::image::Wcs&, int, const lsst::afw::geom::Box2I&, int) [with MatchT = lsst::afw::table::Match] Number of matches less than requested sip order {0} lsst::pex::exceptions::LengthError: 'Number of matches less than requested sip order' {code} {code:title=HSC fit: visit=19696 ccd=103} 2016-06-10T17:20:11: processCcd.calibrate.astrometry: Found 84 catalog sources 2016-06-10T17:20:11: processCcd.calibrate.astrometry: Matching to 137/162 good input sources 2016-06-10T17:20:11: processCcd.calibrate.astrometry: Matched 19 sources 2016-06-10T17:20:11: processCcd.calibrate.astrometry WARNING: Number of matches is smaller than request 2016-06-10T17:20:11: processCcd.calibrate.astrometry: 19 astrometric matches for 103, 1_31 2016-06-10T17:20:11: processCcd.calibrate.astrometry: Refitting WCS 2016-06-10T17:20:11: processCcd.calibrate.astrometry: Astrometric scatter: 0.086131 arcsec (with non-linear terms, 18 matches, 1 rejected) {code} Other failed visit/ccd combos: visit=19684 ccd=101 visit=30488 ccd=95: RuntimeError: Unable to match sources This may simply be due to some threshold in the configs that is rejecting more stars on the LSST side, but this is not confirmed. Please investigate the cause of these failures.
Story points: 6