Project DR-11

Pattern matching for 1D and 2D spectra

Major progress has been performed recently in improving the robustness of wavelength calibration of 1D spectra by means of pattern-matching algorithms (Izzo et al., 2007). The present algorithm is based on Cox et al. (1991) has been tested on a number of instruments (FORS, VIMOS, GIRAFFE, CRIRES, and UVES). It could be further improved to cope with non-linearities of the dispersion relation and possibly by using more recent pattern-matching algorithms.

This project aims at providing methods for 2D pattern-matching in astronomical images (see e.g. Cox & de Jager 1993, Proc. South African Symp. on Communication and Signal Processing, p. 243). Applications to be investigated are in the area of multi-object spectroscopy (pattern-matching between slit masks and spectra) and the identification of objects in images.
 

References

• Izzo, C., et al., 2007, A bottom-up approach to spectroscopic data reduction. The 2007 ESO Instrument Calibration Workshop, eds. A. Kaufer & F. Kerber, Springer Verlag, 2008, p. 191 (http://www.eso.org/sci/meetings/cal07/presentations/moses.pdf)
• Cox and Jager, 1991, A New Method of Rotation, Scale and Translation Invariant Point Pattern Matching Applied to the Target Acquisition and Guiding of an Automatic Telescope
• Cox, 1995, A Survey of Point Pattern Matching Techniques and a New Approach to Point Pattern Recognition
• http://www.dip.ee.uct.ac.za/imageproc/pattern/point.html

Applicable instruments and modes

FORS, VIMOS spectroscopy, and in general all spectrographs (GIRAFFE, CRIRES, UVES, SINFONI etc..). Archive imaging data (FORS, VIMOS, etc..)
 

Required archive, calibration or observation data

Archived wavelength calibration data for the above-mentioned instruments.

 

Required algorithm developments

Evaluate recent and state-of-the-art pattern-matching algorithms, verify performance on different instruments and settings. Algorithms should be evaluated both for arc-line and sky-line based calibrations (1D-matching), and for wavelength calibration and star detection (2D-matching). In order to support the tasks DR-01, DR-02, priority shall be given to the 2D-matching, and aim at resolving the issues identified by these projects.

A method of pattern-matching has been integrated in the ESO Common Pipeline Library (www.eso.org/cpl) and is currently used both for 1D applications (e.g. FORS wavelength calibration) and for 2D applications (X-Shooter bootstrap, FORS, and WFI astrometry standard detections).
 

Required software developments

This project will provide a mathematical description of the algorithms, as well as prototype code of the algorithms (e.g. based on C-code, optionally prototyped in CPL), and a test report.

Validation

The performance of the new algorithms will be compared to the existing CPL pattern-matching implementation with regard to speed, robustness, and accuracy of the matches. The suitability of the proposed methods for the existing applications (FORS, WFI, and X-Shooter) shall be demonstrated in the test reports.