GIRAFFE and FLAMES-UVES data reduction

The ESO FLAMES-UVES pipeline

The UVES pipeline Data Reduction Software (DRS) was originally implemented around the UVES context of MIDAS and is an evolved version of the ECHELLE context. The latest MIDAS version is 2.9.10 (2012-06-13). It is designed to automatically reduce point source object spectra from UVES slit and slicer raw frames to order extraction and final order merging.

The most uptodate version however uses the common pipeline language (CPL) which can be used using either gasgano or esorex. The latest version is 5.0.9 (2012-05-31). The UVES pipeline supports both UVES standalone plus the reduction of the FLAMES-UVES fibre mode data. A reflex workflow will be available soon. 

Check the Status of the VLT Instrument Pipelines for latest news and download details.

The ESO FLAMES-GIRAFFE pipeline

The ESO GIRAFFE pipeline is based on the GIRAFFE BLDRS. Its current version is 2.9.2 (2012-05-31). The ESO pipeline however has the advantage to allow for data reduction in a user-friendly way through Gasgano (GUI for data browsing and organisation). Alternatively, the pipeline recipes can be embedded into scripts for automatic data reduction via the command-line utility EsoRex.

More information on the  GIRAFFE KIT (which includes the pipeline recipes, Gasgano, EsoRex and the calibration data base) is available at  Status of the VLT Instrument Pipelines

The GIRAFFE BLDRS at Geneva Observatory

Click here for general information on the Geneva Giraffe data reduction system.

The software package can be downloaded from SourceForge.

NOTE: This standalone data reduction system is developed, distributed, and maintained by the Geneva Observatory. No support from ESO is available for this software.

The FLAMES fibre binary table FITS extensions

The FITS header of every FLAMES-GIRAFFE and FLAMES-UVES file contains all information related to the fibres in two FITS extension tables:

  1. the OzPoz table: it relates objects on the sky and fibre buttons in Ozpoz.
  2. the (static) FLAMES FIBRE Table: it relates the fibre buttons on Ozpoz and the fibre positions in the slits

Information on the structure of these tables and examples can be found here.

How do I access FITS binary table extensions ?

  • the ESO Skycat tool allows to load and display FITS files with image and table extensions.
  • the ESO MIDAS data processing system allows to extract the FITS extensions into normal image frames and tables. E.g. to split a GIRAFFE FITS file into its extensions, type
    Midas 001> INDISK/FITS GIRAF.2003-04-01T12:34:56.789.fits giraf
    FITS file: 2003-04-01T12:34:56.789.fits converted to: giraf.bdf
    FITS file: 2003-04-01T12:34:56.789.fits converted to: giraf.tbl
    FITS file: 2003-04-01T12:34:56.789.fits converted to: girafa.tbl
    where the image file is stored as giraf.bdf, the OzPoz table as giraf.tbl and the FLAMES FIBRE Table as girafa.tbl.
  • the IRAF data processing system allows to extract the FITS extensions into normal image frames and tables. E.g. to split a GIRAFFE FITS file into its extensions, type
    strfits FLAMES_GIRAF_OBS149_0006.fits 1 giraf xdimtog- oldiraf- force+
    strfits is part of the Space Telescope stsdas.fitsio package.
    The image file is then stored as giraf.hhh, the OzPoz table as giraf01.tab and the FLAMES FIBRE Table as giraf02.tab. All three files are stored in IRAF image and table format and can be processed with the standard IRAF tasks.
  • the FITSIO libraries allow you to access any FITS file and its data extensions from your own C and FORTRAN code.
  • ...

How do I find out which spectrum corresponds to which object ?

  1. determine the Slit used for the observation:
    • GIRAFFE: read the FITS header keyword ESO.INS.SLIT.NAME which indicates the fibre type used (Medusa, IFU, ARGUS) and the number of the respective OzPoz plate.
    • UVES: read the FITS header keyword ESO.INS.SLIT3.PLATE which indicates if the UVES slit 1 or the UVES slit 2 was used, corresponding to the respective OzPoz plate.
  2. determine the fibre position of the spectrum in the slit FPS:
    the easiest way is to use a fibre flatfield which is delivered as one of the standard calibration products. Match the position of the object spectrum with the position of the flatfield and determine its number in the slit:
    • For GIRAFFE IFU and MEDUSA you have to start counting from the left to the right; the first spectrum on the chip is from a simultaneous calibration lamp.
    • For GIRAFFE ARGUS, you have to start counting from the right; the first spectrum on the chip is from a ARGUS sky fibre. However, this fibre is currently disabled because of its low transmission and its location at the edge of the chip.
    • For UVES you have to start counting from the right to the left within one order. If you have used a simultaneous calibration fibre mode (UVES 7+1), the first fibre is the calibration fibre which is counted as number 1. In all other UVES modes (UVES 8, UVES 6), the simultaneous fibre is not visible and the first fibre is counted as number 2. This means e.g. in the mode UVES 8 your will find the fibres 2-9 on the flatfield as counted from the right to the left.
  3. now match Slit and FPS with the respective columns of the FLAMES FIBRE Table and retrieve the corresponding retractor position RP of the fibre button. This number corresponds to the fibre number which was assigned to the object by FPOSS. Note that in FPOSS, the retractor position is also called the Pivot number.
  4. the last step is to match RP with the column BUTTON of the OzPoz Table to find the row of the table which contains the Object name and further information related to that object and its assigned fibre button during the actual observation.

How do I construct the ARGUS data cube ?

  1. determine the FPS of the individual fibres as described above
  2. for the slit Argus the FLAMES FIBRE Table provides two additional columns, X and Y which indicate the spatial position of the fibre in the ARGUS matrix.
  3. if the extracted spectra are arranged in the data cube with the given x, y coordinates, a reconstructed ARGUS image is oriented with N-S along the long side and E-W along the short side for a ARGUS position angle of PA=0. The position angle is counted in standard sense, i.e., from N over E. The actual position angle of the observations is reported in the FITS header of the OzPoz Table in the keyword ARGS.POSAN.