1. STScI TIPS, 15 January 2004MultiDrizzle Overview - Anton Koekemoer1 MultiDrizzle Status and Development Overview Anton Koekemoer, ACS+WFPC2 Branch Project Overview –Forum: Dither Working Group –Software Development Mechanism –Development Timeline to Date MultiDrizzle Requirements –General –Instrument-Specific Considerations MultiDrizzle Testing –General Overview –Instrument-Specific Considerations Priorities and Timescales –Development and Testing –Documentation –Community Feedback Roadmap for Future Development

2. STScI TIPS, 15 January 2004MultiDrizzle Overview - Anton Koekemoer2 MultiDrizzle Project Overview Forum - Dither Working Group (established January 2002): –Purpose:  Coordinate development & implementation of fully integrated software to automatically register, CR clean and combine dithered HST images (software intended as successor to CL-based STSDAS “dither” pkg) –Process:  Provide forum for dialog between INS, SSB, and dither software users  Define requirements and set priorities for development and testing  Determine roadmap for implementation, distribution, documentation –Membership:  Representatives from INS, SSB, + others attending as needed Development Mechanism: –MultiDrizzle requirements initially developed through discussions within Dither Working Group and interations with users –MultiDrizzle prototype (Koekemoer, Fruchter, Hook et al.) developed to demonstrate desired functionality; beta release under STSDAS –SSB redesigns the code, reproducing the functionality of prototype –Continual testing by SSB and INS, and dialog with external users

3. STScI TIPS, 15 January 2004MultiDrizzle Overview - Anton Koekemoer3 MultiDrizzle Project Organization

4. STScI TIPS, 15 January 2004MultiDrizzle Overview - Anton Koekemoer4 MultiDrizzle Development to Date Jan - May 2002: –Definition of MultiDrizzle requirements in Dither Working Group –Initial prototype MultiDrizzle (Koekemoer, Fruchter, Hook et al.) Jun - Sep 2002: –Distribute prototype to variety of GOs: GOODS, GEMS, High-Z SNe, GRBs, APPLES, Helix Nebula; external GOs at GSFC, CfA, Caltech,... Oct - Dec 2002: –Announce general availability to GOs on beta-test basis (Cal Wkshp) –Initial suite of ACS, WFPC2 test datasets Jan - Jun 2003: –Hand over prototype to SSB for inclusion in STSDAS (Hack et al.) –More user feedback, improve robustness, refine testing Jul 2003 to present: –SSB redesign of MultiDrizzle code (Hack, Hanley et al.) using prototype MultiDrizzle as a basis for defining functionality –Develop formal regression test suites

5. STScI TIPS, 15 January 2004MultiDrizzle Overview - Anton Koekemoer5 MultiDrizzle Requirements - General Fundamental Requirements: –Combine arbitrary collections of images (including single-group) –Automatically calculate required output image size –Determine shifts from headers –[Optionally refine shifts or allow input delta-shifts] –Carry out sky subtraction on input images –Automatically perform CR rejection:  Drizzle input exposures onto separate, registered output images  Create a clean “median” image  Blot the clean image back to frame of each individual exposure  Run deriv, driz_cr to create cosmic ray masks  Use CR masks in final drizzle combination –Allow external bad-pixel masks to be imported –Allow individual steps to be selected when running Overall philosophy: –Allow user freedom in specifying behavior via parameters –Defaults must enable good results from “one-touch” operation

6. STScI TIPS, 15 January 2004MultiDrizzle Overview - Anton Koekemoer6 Requirements – Instrument-Specific ACS –Accurately handle WFC, HRC, SBC imaging data –Single-group images (eg only [sci,1]) –Sub-array data –Include new geometric distortion-residual images (Anderson) WFPC2 –Handle 4-group WFPC2 GEIS as well as FITS format files –Single-group images (eg WF3 only) –Sub-array data –Include updated geometric distortion (Platais et al) NICMOS –NIC1, NIC2 or NIC3 imaging –Ability to handle multi-accum datasets STIS –CCD as well as FUV, NUV-MAMA datasets –Imaging (initially) as well as 2d spectroscopy data (later)

7. STScI TIPS, 15 January 2004MultiDrizzle Overview - Anton Koekemoer7 MultiDrizzle Testing- General Overview Basic Functionality: –Do new versions run successfully for small subset of test datasets? Extended functionality: –Do new versions work for the full range of datasets? Functionality tests can be automated by regression: –Run automatically on a periodic basis –Comparison performed automatically with reference test images, and results reported in summary form Scientific integrity: –Do functional versions deliver scientifically valid results? –Different target types:  Sparse extra-galactic fields, crowded stellar fields  Large extended objects or diffuse emission across entire field Scientific tests require additional analysis, eg: –PSF measurements of stars to ensure shifts, etc are correct –x,y position comparisons to verify correct astrometry

8. STScI TIPS, 15 January 2004MultiDrizzle Overview - Anton Koekemoer8 Testing – ACS + WFPC2 ACS WFC, HRC, + WFPC2: –Basic datasets:  2-point line dither  4-point box dither (single-visit) –More advanced datasets:  Single-visit, small offsets, higher number of dithers  Single-visit, large offsets (comparable to chip size)  Multi-visit, small + large offsets –Number of images:  Small datasets (2-3 exposures total)  Medium datasets (4-6 exposures total)  Large datasets ACS testing lead: Shireen Gonzaga WFPC2 testing lead: Vera Platais

9. STScI TIPS, 15 January 2004MultiDrizzle Overview - Anton Koekemoer9 Testing (cont’d) - NICMOS, STIS NICMOS: Imaging - NIC1, NIC2, NIC3: –Multi-accum datasets –Different dither patterns (spiral) –Large-scale + small-scale dithers to account for chip defects NICMOS testing lead: Megan Sosey STIS CCD + MAMAs: Imaging: –Mostly large-scale dithering Spectroscopy: –Dithering along slit –Dithering along spectral direction –CTE: CRs, bad pixels are a major issue (since low background) STIS testing lead: Linda Dressel

10. STScI TIPS, 15 January 2004MultiDrizzle Overview - Anton Koekemoer10 Priorities and Timescales Development and Testing: Near-term (+ 1 month): –INS: Identify test datasets and create baseline results –SSB: Include tests in regression mechanisms –SSB: upgrade current beta-release MultiDrizzle to fully supported Long-term: –Maintain database of reference results –Update test database when warranted by code changes –SSB release redesigned MultiDrizzle: for users and HST pipeline Documentation: –Release TIR describing development plans for MultiDrizzle –Release updated Dither Handbook V3.0 to user community, with full description of the use of MultiDrizzle Community Feedback: –Continue to collect suggestions and feedback from users –Incorporate into regular prioritization planning

11. STScI TIPS, 15 January 2004MultiDrizzle Overview - Anton Koekemoer11 Proposed Roadmap for Future Development Mar 2004: –SSB to upgrade original “prototype” MultiDrizzle to a fully supported version (eg via patch release, and/or from STSDAS website) –INS to release updated Dither Handbook V3.0 with full description of the use of MultiDrizzle software Jan - Jun 2004: –INS provide test datasets to SSB (near-term), update as necessary –SSB to complete the redesigned MultiDrizzle as user software –SSB to release redesigned MultiDrizzle in Summer 2004 STSDAS Jul - Sep 2004: –SSB, INS work on more robust, streamlined MultiDrizzle for fully automated use in HST Pipeline Operations –Continue to incorporate feedback and usage patterns from GOs Oct 2004 onwards: –Continuing algorithmic development to improve software, eg:  tweakshift (automated catalog-based shift refinement)  more robust CR rejection techniques for few-exposure datasets