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

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

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

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

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

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)

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

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

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

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

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