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AstroDrizzle Products for HST & JWST 2014 STScI Calibration Workshop Jennifer Mack, STScI

AstroDrizzle Products for HST & JWST 2014 STScI Calibration Workshop Jennifer Mack, STScI. AstroDrizzle. Part of the DrizzlePac software package, a suite of tasks for aligning & combining images July 2012: AstroDrizzle replaced MultiDrizzle in the pipeline

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AstroDrizzle Products for HST & JWST 2014 STScI Calibration Workshop Jennifer Mack, STScI

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  1. AstroDrizzle Products for HST & JWST2014 STScI Calibration WorkshopJennifer Mack, STScI

  2. AstroDrizzle • Part of the DrizzlePacsoftware package, a suite of tasks for aligning & combining images • July 2012: AstroDrizzlereplaced MultiDrizzlein the pipeline • More accurate handling of image distortion • Resolves astrometric errors in prior pipeline products ~1-3 pixels • Only AstroDrizzle supports the latest distortion corrections

  3. Distortion Linear Terms: CD Matrix Non-Linear Terms: 4th order polynomial solution uses SIP convention • --> imheader *flc.fits[1] l+ • IDCTAB = 'jref$v8q1444sj_idc.fits' • CTYPE1 = 'RA---TAN-SIP' • CTYPE2 = 'DEC--TAN-SIP' • CRPIX1 = 2048.0 • CRPIX2 = 1024.0 • CRVAL1 = 3.570976354857465 • CRVAL2 = -30.40853421183697 • CD1_1 = -1.2368663915761E-05 • CD1_2 = 5.40792001738662E-06 • CD2_1 = 6.22592168300775E-06 • CD2_2 = 1.28863357087715E-05 • A_ORDER = 4 B_ORDER = 4 • A_0_2 = 2.15855556719611E-06 B_0_2 = -7.2205055908409E-06 • A_1_1 = -5.1799259715535E-06 B_1_1 = 6.18651663667832E-06 • A_2_0 = 8.54735349534391E-06 B_2_0 = -1.7316236718108E-06 • A_0_3 = 9.48132134575003E-12 B_0_3 = -4.0744859582615E-10 • A_1_2 = -5.2350450605432E-10 B_1_2 = -6.7147082489847E-11 • A_2_1 = -4.4750751791397E-11 B_2_1 = -5.0664045452596E-10 • A_3_0 = -4.7306614567992E-10 B_3_0 = 8.84394906333280E-11 • A_0_4 = 1.31172591483522E-14 B_0_4 = -9.8894110757065E-15 • A_1_3 = -2.3901889495070E-14 B_1_3 = 1.26720582177971E-14 • A_2_2 = 3.79343576547842E-14 B_2_2 = -3.7703000929016E-14 • A_3_1 = 3.81170188644090E-16 B_3_1 = -3.1721984142757E-15 • A_4_0 = 2.32007544572055E-14 B_4_0 = -1.8758253622538E-14 Meurer et al. 2002 HST Cal Wkshp

  4. Distortion Non-polynomial lookup tables in new FITS extensions -- > catfits *flc.fits EXT# FITSNAME FILENAME EXT DIMENSION 0 jb5g08z2q jb5g08z2q_flc 1 IMAGE SCI 1 4096x2048 2 IMAGE ERR 1 4096x2048 3 IMAGE DQ 1 4096x2048 4 IMAGE SCI 2 4096x2048 5 IMAGE ERR 2 4096x2048 6 IMAGE DQ 2 4096x2048 7 IMAGE D2IMARR 1 4096x1 8 IMAGE D2IMARR 2 4096x1 9 IMAGE WCSDVAR 1 65x33 10 IMAGE WCSDVARR 2 65x33 11 IMAGE WCSDVARR 3 65x33 12 IMAGE WCSDVARR 4 65x33 Kozhurina-Platais et al. WFC3 ISR 2013-04 • ‘Detector to Image’ correction • WFC3/UVIS lithographic mask pattern • ACS/WFC column width correction • Filter-residual lookup tables (DGEOFILE)

  5. Pipeline Products Drizzled data products for ‘singles’ and ‘associations’ Image associations are at the ‘visit level’ only 1.) Defined by the user at Phase II via PATTERNs, CR-SPLITs, RPT-OBS e.g. IR-BLOB-DITHER, UVIS-DITHER-BOX 2.) Additional rules defined by the instrument teams e.g. WFC3 images in same visit & filter

  6. Pipeline Products MAST products use default AstroDrizzle parameters for general use • Defined in MDRIZTAB reference file • One MDRIZTAB per detector • Rows select for number of input frames N=1,2,6 ACS/WFC, WFC3/UVIS N=1,2,4 WFC3/IR

  7. Multi-Visit Programs • TweakReg not run in OPUS  visit-level DRZ products only • Strongly recommend updating the header WCS before combining Typical HST pointing (with fine-lock on 2 guide stars) Observing ScenerioRMS Precision . (mas) (UVIS pix) Same orbit (dither < 1”) 2-5 0.1 Re-acq for orbits in same visit 5-20 0.1-0.4 Diff visits, same guide stars, same orient 50-100 1.2-2.5 Diff guide stars 200-500 5.0-12.5

  8. Why reprocess? • Fine-tune alignment(cross-visit, cross-filter, cross-detector) • Match sky background (reduced correlated noise, better CRREJ) • Select bad pixel flags • Improve CR rejection • Stack many visits;build mosaics • Optimize final scale/pixfrac(PSF resampling)

  9. Single Exposures • Drizzling resamples the PSF • Redistributes flux onto uniform output grid • Corrects distortion • Convolves with mathematical kernel • Result: Blurs PSF slightly; adds correlated noise • For N=1, users may prefer to use FLT*PAM for photometry • Else tell drizzling software to ignore DQ flags set in CALxxx pipeline

  10. N=1: DRZ photometry of singles Dither 2 WFC3 UVIS AstroDrizzle rejects hot pixels DQ flag =16 Dither 1 Hot Pixels 1% low 3% low

  11. N=1: DRZ photometry of singles Ignore hot pixel Reject hot pixel

  12. N=1: DRZ photometry of singles Relative photometry of 47 Tuc ACS ISR 2007-02 (Mack et al.) Ignore DQ flags (treat all pixels as ‘good’) Use DQ flags (treat flagged pixels as ‘bad’) mag Delta mag Delta mag

  13. N=2: Intra-pixel centering UVIS-DITHER-LINE (2.5 pix in x & y) FLT*PAM, aperture photometry r=10 pix # asn_ID (xc, yc) Peak (e-) Flux (e-) Mag FWHM im1 ic5pa1060 (0.6,0.6) 34331267101 11.43 2.1 pix im2 (0.0,0.0) 47900264994 11.44 1.5 pix 40% <1%

  14. N=2: Intra-pixel centering • Star at corner vs center of pixel • Core of sharper PSF flagged as CR • Replaced with core from broader PSF • Result: Photometry 4% too low in combined image X,Y = (0.6,0.6) FWHM= 2.1 pix Peak = 35 Ke- X,Y = (0.0,0.0) FWHM= 1.5 pix Peak = 48 Ke- driz_cr_scale= 1.2, 0.7 driz_cr_scale= 2.0, 1.5 driz_cr_scale= 3.0, 2.5 FLT DRZ DQ WHT

  15. N=3+ exposures For dither patterns which optimally sample the PSF Shrinking the ‘pixfrac’ can sharpen the image Pipeline defaults ACS/WFC, WFC3/UVIS: Pixfrac = 1.0 for N < 6 WFC3/IR: Pixfrac = 1.0 Pixfrac =‘drop’ size relative to input pixel Red: pixfrac = 1 Blue: pixfrac < 1

  16. IR-DITHER-BOX-MIN Final Scale/ Pixfrac WFC3-IR-DITHER-BOX-MIN Provides optimal 4-step sampling of the PSF. Y (pix) X (pix) Pipeline Product FWHM = 0.19” Scale = 0.128” Pixfrac = 1.0

  17. IR-DITHER-BOX-MIN Final Scale/ Pixfrac WFC3-IR-DITHER-BOX-MIN Provides optimal 4-step sampling of the PSF. Y (pix) X (pix) Optimized Product FWHM = 0.18” Scale = 0.064” Pixfrac = 0.8

  18. Sky Subtraction • Large dithers changes the ‘scene’ • True background may be difficult to determine for extended sources • Solution: 1.) Provide user-determined background values via ‘skyfile’ • 2.) Try new sky matching in DrizzlePac2.0 • (Uses only pixels in common between exposures) localmin match min+match Note: When sky not matched  Poor cr-rejection & photometry; correlated noise

  19. Release History June 2012: v1.0 Sept 2013: v1.1.12 Corrects 2-D lithographic pattern for WFC3/UVIS data (Kozhurina-Platais et al. WFC3 ISR 2013-04) Jan 2014: v1.1.16 Currently in MAST Available via Urekahttp://ssb.stsci.edu/ureka Aug 4, 2014: v2.0.0 Available only as Ureka development version (SSBX) • Supports *new* ACS time-dependent distortion • (Kozhurina-Platais et al., ACS ISR in prep) • New sky matching • Align 2 detectors in 1 step • New iterative solutions for aligning mosaics • Improved source matching when CR’s dominate point sources

  20. ‘Enhancing the Past, Maximizing the Present…’ Development in progress: • Improved MAST products via new MDRIZTAB defaults Add rows for # input frames Currently n=1,2,6; Add n=2,3,4,5 Add rows for patterns IR-BLOB-DITHER, UVIS-DITHER-BOX Add columns for new parameters • Improved software TweakReg: Weightsources by brightness TweakReg: Support full 6-parameter solution to remove skew AstroDrizzle: Parallelize all steps to improve run times

  21. ‘…Preparing for the Future’ MAST supports Headerlet files • Small FITS files representing a single WCS solution • AstroDrizzle supports multiple solutions (WCSNAME) Eg: GAIA absolute reference frame

  22. New Drizzling Forum http://forum.stsci.edu/ • New way of communicating with users • Allows more dynamic information flow • Ideal to support v2.0 software release (Aug 2014) • Open discussion develops a ‘community’ of drizzlers • To go live by end-Aug

  23. JWST.. DrizzlePac development for JWST is in early stages Associations • HST: at visit level • JWST: by proposal, target, detector, filter TweakRegwill be run in the pipeline for multi-visit programs Drizzled products will continually evolve to include all exposures to date Multi-epoch associations will allow for improved CR-rejection As for HST, headerletscan provide alignment to absolute reference frame

  24. Zazzle.com JWST.. Distortion • Same WCS keywords (linear terms in CD-Matrix) • Higher order distortion in separate extension Support different FITS format than HST • MIRI, NIRSPECIFU’s will have 3D drizzled products • (science array=3D cube in RA, Dec, lambda) NIRSPEC – 2 options for users • (drizzle all frames together, then extract spectrum) • (drizzle singles, extract spectra, then coadd) • NIRCAM, NIRISS slitless spectroscopy handled similar to ACS,WFC3 grisms • For more info: Howard Bushouse (Calibration pipeline) Warren Hack (DrizzlePac)

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