During and after the observing run this logbook should be used by the pipeline reduction process. It can identify the best currently available calibration frames of each type, and use that information to control the pipeline.
The DEIMOS slitmask database, catalog, and the associated WCS should permit complete automation of the spectral identification and extraction. Reasonably accurate positions of the individual spectra will be known in advance, and they can be converted into the database format used within IRAF multispectral extraction. Reasonably accurate wavelength and dispersion calibrations will also be known in advance, and these can be used for automatic identification of calibration lamp or night sky lines.
For spectral frames the pipeline should first produce a calibrated image
with the characteristics described above.
It should then make use of the slitmask and grating
information to predict the location of each slitlet spectrum.
With DEIMOS spectra it should not be necessary to run IRAF tasks from the
package to find and trace spectra. Similarly, it should not be
necessary to run the
task to establish the wavelength scale.
The pipeline should produce extracted spectra for each slitlet. If the object catalog contains sufficient information to determine the extent of the object the pipeline may make use of the catalog information about the position and extent of the object to produce sky-subtracted spectra.
The observer should be permitted to modify or replace the default operation of the Night mode to satisfy personal tastes. In addition to the calibration operations listed above observers may often wish to apply a sky subtraction algorithm.
Consistency of the archival data set is important. Re-reduction of older data to a new archival standard may not be feasible. In order to assure consistency the procedures in the archival pipeline should be defined as well as possible before the the first scientific data are acquired. Changes to the archival pipeline should be infrequent.
Whether or not DEIMOS has long-term stability of its calibrations
the Information Management system described in Chapter 9
is an essential component of the pipeline.
The classification and selection of calibration frames should be
done at the time of observation by DEIMOS rather than at the
end of the observing run by
Similarly, the enumeration and detection of the multislit spectra will be
done at the time of observation rather than by
The logbook tables from DEIMOS should be designed with the expectation
that they can be converted into IRAF parameter files and IRAF
twodspec databases. It should be
possible to construct IRAF parameter files for each of the tasks
ccdproc and the spectral reduction packages. This
should drive the pipeline through the basic CCD reduction operations.
The Information Management system (Chapter 9) is absolutely essential to the success of the pipeline. Its database must be able to construct tables that describe the relationships between a particular CCD readout and other CCD readouts.
The results of the pipeline will be saved using the archiving system (Chapter 9).
The characterization of the instrumental stability will require significant effort. Thousands of images taken repeatedly under conditions that span the range of possible configurations will be needed. In order to keep the labor requirements manageable this sequence of calibrations should be obtained by an automated procedure.
The Information Management system will be indispensable. It will be needed for answering questions about the differences between calibration frames that should be similar, and the similarities of calibration frames that should differ. It will also be needed for keeping track the configurations in which calibration frames have been obtained and for determining if there are any configurations for which there are no calibration frames.
In the absence of a calibration library which is stable over the long-term it will be necessary for observers to acquire their own calibration frames. Operation of a calibration pipeline will be difficult if the expected inputs are not obtained. This will require cooperation from the observers, the observing assistants, and support from CARA.