Using the FEROS software on-line at the telescope

This section briefly describes the on-line operation of the FEROS software at the ESO 1.52m telescope. For a full documentation of FEROS see:

http://www.ls.eso.org/lasilla/Telescopes/2p2T/E1p5M/FEROS/docu/pages/frames.html

The FEROS on-line DRS allows a complete reduction of the science spectra taken during the night from the CCD system. The on-line DRS is based on the MIDAS context feros.

To install the on-line software after the DRS is installed, the MIDAS programs of the directory

$MIDASHOME/$MIDVERS/stdred/feros/locproc

have to be copied to the local midwork directory.

After CCD readout, the BIAS program

• includes the status informations from the CCD, the Telescope Control System (TCS), and the Instrument Control System (ICS) in the FITS header
• transfers the 2-D spectra to the instrument workstation (IWS) if the remote autosave is turned on (BIAS command remsave+).
• starts on the IWS the MIDAS programm @@ loadccd fero [filenum] where filenum is the running 4-digit filenumber of the CCD frame.

The loadccd program itself

• loads the frame fero[filenum].mt into the display,
• adds the incoming file to the catalogue Feros.cat,
• writes the FITS file to the DAT drive /dev/rmt/1mn (BS 2880)
• starts the automatic reduction via
• @@ autoreduce fero [filenum]

According to the four possible exposure types (FLATFIELD, CALIBRATION, DARK, and SCIENCE) given in the descriptor EXPTYPE, the autoreduce program starts the following actions:

• FLATFIELD: adds the incoming file to the catalogue FF.cat
• CALIBRATION: adds the incoming file to the catalogue ThAr.cat
• DARK: adds the incoming file to the catalogue Dark.cat
• SCIENCE:
  • adds the incoming file to the catalogue Objects.cat
  • start the pre-reduction of the the file (@@ prered [filenum] raw_image) where raw_image is the name of the input file for the following on-line reduction.
  • computes the barycentric velocity according to the telescope position and writes the result to the descriptor BARY_CORR
  • computes and subtracts the interorder background of the echelle spectrum (BACKGR/FEROS)
  • extracts the echelle orders (RECTIFY/FEROS, EXTRACT/FEROS)
  • removes the blaze function and the pixel-to-pixel variations (FLAT/FEROS)
  • rebins the echelle orders to wavelengths (REBIN/FEROS) according using pre-determined dispersion coefficients. In this step also the barycentric correction is applied.
  • merges the echelle orders (MERGE/FEROS) into two 1-D spectra named f[filenum]1 and f[filenum]2 where the spectrum with the ending 1 refers to the spectrum recorded on the object fiber and the spectrum with the ending 2 to the spectrum recorded on the sky/calibration fiber.

This standard reduction is controlled by the FEROS context keywords which can be listed together with their current contents by the command SHOW/FEROS and are set with the command SET/FEROS key=[value]. See below for useful keywords to be used during the observing session.