Initialization of the DRS at the beginning of the night

To use the automatic data reduction as described above, the DRS has to be initialized at the beginning of the night.

For this purpose several flat-field and wavelength calibration exposures have to be taken in the Object-Sky mode of FEROS before the beginning of the night following the following sequence:

• Reset the image catalogues FF.cat, ThAr.cat, Dark.cat, Object.cat with the command @@ init ? reset
• Insert a new write-enabled DAT in the drive /dev/rmt/1m. Note that this DAT will be overwritten from the beginning erasing any previous contents! One 60m DAT can carry about 70 files. If you are to take more than 70 full frames, it is advisable to change the DAT before it is full.
• Use the instrument control software XFCU running on the CCD control PC next to the ISW to turn on the wavelength calibration lamp and use the BIAS CCD control software to take several (typical 2) exposures of 15 sec each. For details on the XFCU software and the BIAS software see the FEROS documentation. The resulting frames are automatically transfered to the IWS and added to the catalogue ThAr.cat.
• Switch with the XFCU program to the flatfield lamp and take, depending on the S/N needed for a appropriate reduction of the planned science exposures, 3 to 10 exposures of 30 sec. The frames are automatically transfered to the IWS and added to the catalogue FF.cat.
• Initialize the DRS for the night with the command @@ init [guess] where guess is the name of a previously saved guess session. Typically this is the session saved in the night before. The session names are formed automatically from the file number of the first calibration exposure in the catalogue ThAr.cat and the prefix ThAr, e.g., ThAr0741.

Now the following initialization steps are performed

• Initialization of the session keywords and tables (INIT/FEROS)
• Averaging of the frames of the respective catalogues FF.cat, ThAr.cat.
• Setting of the CCD gain keyword according to descriptor CCD_GAIN and the values specified in init.prg
• Definition of the echelle orders in the averaged flatfield (DEFINE/FEROS); the fitted positions are shown in the display window.
• Standard reduction of the flatfield (BACKGR/FEROS, RECTIFY/FEROS, EXTRACT/FEROS). The extraction is done twice: the first time, the cross-order profiles are determined for an optimum extraction with cosmic removal for the science exposures; the second time the flatfield orders are extracted. The name of the reduced flatfield is found in the keyword FLAT_IMG.
• Standard reduction of the wavelength calibration (BACKGR/FEROS, RECTIFY/FEROS, EXTRACT/FEROS). The name of the reduced calibration is found in the keyword WLC_IMG
• Search for emission lines in the reduced calibration frame (SEARCH/FEROS).
• Wavelength calibration by iterative fitting of the dispersion coefficients (CALIBRATE/FEROS). The resdiuals of the individual lines are plotted over the order number. The spread should not exceed an rms of 0.05 Å.
• The session parameters are saved as session WLC_IMG.

With this step completed, the FEROS on-line DRS is initialized.

Every new incoming spectrum will be saved and reduced now as described above.