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WCSFixer - A Web-enabled IRAF Plate Solver

T HE US N ATIONAL V IRTUAL O BSERVATORY. WCSFixer - A Web-enabled IRAF Plate Solver. Michael Fitzpatrick NOAO. Introduction.

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WCSFixer - A Web-enabled IRAF Plate Solver

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  1. THE US NATIONAL VIRTUAL OBSERVATORY WCSFixer - A Web-enabled IRAF Plate Solver Michael Fitzpatrick NOAO IVOA Interop - Victoria, BC

  2. Introduction Final-year planning for the NVO by its Science Steering Committee identified a number of capabilities desirable as end-user applications. The ability to automatically correct (or determine) the astrometric solution of image data ranked as a high-priority task. Much of the needed functionality already existed in IRAF, but some level of interactive use is needed since no automated solution can be completely robust for all available VO data. The challenge then was to implement the desktop reduction experience in the web browser while still providing a batch mode for processing large numbers of images as web services or from client code. IVOA Interop - Victoria, BC

  3. Implementation - CGI/POST web interface • Does form processing, some interface elements - IRAF CL scripts to implement functionality • #!cl script to define IRAF environment prior to calling standard task • Same scripts run unchanged in IRAF desktop env • Host tools (e.g. STILTS, Sextractor available, image conversion tools) - Embedded JavaScript output to drive interface - CSS to aid layout/appearance IVOA Interop - Victoria, BC

  4. Real-World Data Example Problems encountered (and solved): • DSS images have no WCS keywords • CFHT data contain a 64-bit integer id as a keyword (non-standard) • Axis mappings (RA/Long not always first axis) • WCS Projections not handled by IRAF • X-ray data not suited to Sextractor-like object detection • Star trails and focus problems • “Junk Strip” in WFPC data • False solutions -- rms of fit not a good indicator • Large parameter space • Legacy keywords • Use of RA/DEC not standard • specific IRAF keywords (e.g. DATASEC) no longer valid IVOA Interop - Victoria, BC

  5. Spin-off Applications/Services • Image catalog generation/crossmatch • WCS Summary • Preview image • WCS manipulation • Tweak existing WCS (from test app) • Swap axes • Change projection/epoch • Multiple deployments • Web application • SOAP/WSDL web service • Desktop app in IRAF environment IVOA Interop - Victoria, BC

  6. Lessons Learned • Problem itself is a rich area of research • Labor-intensive way to develop • In part because of this particular problem • Re-use in other deployments a bit if an offset • New appreciation for data quality concerns in VO • Legacy techniques and tools can still produce useful VO applications IVOA Interop - Victoria, BC

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