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

2. + AstroDrizzle Part of the DrizzlePac software package, a suite of tasks for aligning & combining images July 2012: AstroDrizzle replaced MultiDrizzle in 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 --> 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 = 4B_ORDER = 4 A_0_2 = 2.15855556719611E-06B_0_2 = -7.2205055908409E-06 A_1_1 = -5.1799259715535E-06B_1_1 = 6.18651663667832E-06 A_2_0 = 8.54735349534391E-06B_2_0 = -1.7316236718108E-06 A_0_3 = 9.48132134575003E-12B_0_3 = -4.0744859582615E-10 A_1_2 = -5.2350450605432E-10B_1_2 = -6.7147082489847E-11 A_2_1 = -4.4750751791397E-11B_2_1 = -5.0664045452596E-10 A_3_0 = -4.7306614567992E-10B_3_0 = 8.84394906333280E-11 A_0_4 = 1.31172591483522E-14B_0_4 = -9.8894110757065E-15 A_1_3 = -2.3901889495070E-14B_1_3 = 1.26720582177971E-14 A_2_2 = 3.79343576547842E-14B_2_2 = -3.7703000929016E-14 A_3_1 = 3.81170188644090E-16B_3_1 = -3.1721984142757E-15 A_4_0 = 2.32007544572055E-14B_4_0 = -1.8758253622538E-14 Linear Terms: CD Matrix Non-Linear Terms:4 th order polynomial solution uses SIP convention Meurer et al. 2002 HST Cal Wkshp

4. + -- > catfits *flc.fits EXT# FITSNAME FILENAME EXT DIMENSION 0 jb5g08z2q jb5g08z2q_flc 1 IMAGE SCI 1 4096x2048 2 IMAGE ERR1 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 D2IMARR2 4096x1 9 IMAGE WCSDVAR 1 65x33 10 IMAGE WCSDVARR 2 65x33 11 IMAGE WCSDVARR 3 65x33 12 IMAGE WCSDVARR 4 65x33 Non-polynomial lookup tables in new FITS extensions Distortion ‘Detector to Image’ correction  WFC3/UVIS lithographic mask pattern  ACS/WFC column width correction Filter-residual lookup tables (DGEOFILE) Kozhurina-Platais et al. WFC3 ISR 2013-04

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. + 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=1,2,6ACS/WFC, WFC3/UVIS N=1,2,4WFC3/IR Pipeline Products

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 Scenerio RMS 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 50-1001.2-2.5 Diff guide stars 200-5005.0-12.5

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 FrameFlux (e-/s)Mag flt1 * pam14021012.13 flt2 * pam14002812.13 drz113988312.14 drz213651212.16 drz1 no_dq14028512.13 drz2 no_dq14013812.13 WFC3 UVIS AstroDrizzle rejects hot pixels DQ flag =16 Dither 1 Dither 2 Hot Pixels 1% low 3% low

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

12. + 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’) Delta mag mag N=1: DRZ photometry of singles

13. + 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) 34331 267101 11.43 2.1 pix im2 (0.0,0.0) 47900 264994 11.44 1.5 pix 40%<1% N=2: Intra-pixel centering

14. + 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 driz_cr_scale= 1.2, 0.7 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- FLT DQ DRZ WHT N=2: Intra-pixel centering driz_cr_scale= 2.0, 1.5 driz_cr_scale= 3.0, 2.5

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 Red: pixfrac = 1 Blue: pixfrac < 1 Pixfrac =‘drop’ size relative to input pixel

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

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

18. + Sky Subtraction localminmatchmin+match Note: When sky not matched  Poor cr-rejection & photometry; correlated noise 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 DrizzlePac 2.0 (Uses only pixels in common between exposures)

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 Ureka http://ssb.stsci.edu/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 framesCurrently 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: Weight sources 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 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. + DrizzlePac development for JWST is in early stages Associations HST: at visit level JWST: by proposal, target, detector, filter TweakReg will 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, headerlets can provide alignment to absolute reference frame JWST..

24. + Distortion Same WCS keywords (linear terms in CD-Matrix) Higher order distortion in separate extension Support different FITS format than HST MIRI, NIRSPEC IFU’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) Zazzle.com