+

AstroDrizzle Products for HST & JWST

2014 STScI Calibration WorkshopJennifer 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

More accurate handling of image distortion Resolves astrometric errors in prior pipeline products ~1-3 pixels Only AstroDrizzle supports the latest distortion corrections

+ 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 = 4 B_ORDER = 4A_0_2 = 2.15855556719611E-06 B_0_2 = -7.2205055908409E-06A_1_1 = -5.1799259715535E-06 B_1_1 = 6.18651663667832E-06A_2_0 = 8.54735349534391E-06 B_2_0 = -1.7316236718108E-06A_0_3 = 9.48132134575003E-12 B_0_3 = -4.0744859582615E-10A_1_2 = -5.2350450605432E-10 B_1_2 = -6.7147082489847E-11A_2_1 = -4.4750751791397E-11 B_2_1 = -5.0664045452596E-10A_3_0 = -4.7306614567992E-10 B_3_0 = 8.84394906333280E-11A_0_4 = 1.31172591483522E-14 B_0_4 = -9.8894110757065E-15A_1_3 = -2.3901889495070E-14 B_1_3 = 1.26720582177971E-14A_2_2 = 3.79343576547842E-14 B_2_2 = -3.7703000929016E-14A_3_1 = 3.81170188644090E-16 B_3_1 = -3.1721984142757E-15A_4_0 = 2.32007544572055E-14 B_4_0 = -1.8758253622538E-14

Linear Terms: CD MatrixNon-Linear Terms: 4th order polynomial solution uses SIP convention

Meurer et al. 2002 HST Cal Wkshp

+

--

> 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

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

+ 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

+

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

Pipeline Products

+ 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

0.1-0.4Diff visits, same guide stars, same orient 50-1001.2-2.5Diff guide stars 200-500 5.0-12.5

+ 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)

+ Single Exposures

Drizzling resamples the PSF Redistributes flux onto uniform output grid Corrects distortion Convolves with mathematical kernel

Result: Blurs PSF slightly; adds correlated noiseFor N=1, users may prefer to use FLT*PAM for photometry

Else tell drizzling software to ignore DQ flags set in CALxxx pipeline

+ N=1: DRZ photometry of singles

Frame Flux (e-/s) Mag

flt1 * pam 140210 12.13

flt2 * pam 140028 12.13

drz1 139883 12.14

drz2 136512 12.16

drz1 no_dq 140285 12.13

drz2 no_dq 140138 12.13

WFC3 UVISAstroDrizzle rejects hot pixelsDQ flag =16

Dither 1Dither 2

Hot Pixels

1% low3% low

+

Ignore hot pixel Reject hot pixel

N=1: DRZ photometry of singles

+

Relative photometry of 47 TucACS ISR 2007-02 (Mack et al.)

Ignore DQ flags(treat all pixels as ‘good’)

Use DQ flags(treat flagged pixels as ‘bad’)

Delta mag Delta mag

mag

N=1: DRZ photometry of singles

+

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 pixim2 (0.0,0.0) 47900 264994 11.44 1.5 pix

40%<1%

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

driz_cr_scale= 1.2, 0.7

X,Y = (0.6,0.6) FWHM= 2.1 pixPeak = 35 Ke-

X,Y = (0.0,0.0) FWHM= 1.5 pixPeak = 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

+ N=3+ exposures

For dither patterns which optimally sample the PSFShrinking 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 = 1Blue: pixfrac < 1

Pixfrac =‘drop’ size relative to input pixel

+ 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.

+

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

+ Sky Subtraction

localmin matchmin+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)

+ 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/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

+ ‘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: Weight sources by brightness

TweakReg: Support full 6-parameter solution to remove skew

AstroDrizzle: Parallelize all steps to improve run times

+‘…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

+ 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

+

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..

+ JWST..

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)

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