This document gives a general introduction to the pipeline, what it does and what it will not do. For information on instrument specific functions, see SUN/231 for SCUBA; SUN/232 for IRCAM, UFTI, Michelle, UIST, INGRID, ISAAC and IRIS-2 imaging; SUN/236 for CGS4, Michelle, UIST and IRIS-2 spectroscopy; and SUN/246 for UIST IFU imaging spectroscopy.
The ORAC-DR data reduction system is intended to be a pipeline reducer for incoming data. It is in use for online data reduction at UKIRT and JCMT for a variety of instruments. There are a number of differences between the ORAC-DR method of reduction and other systems currently in use and observers should not expect ORAC-DR to behave or be used in the same way as those systems.
Firstly, ORAC-DR aims to reduce data to a point where its quality can be assessed; it will not generally produce publication-quality results (though in certain circumstances it may do). Secondly, although ORAC-DR also works offline, it is expected that observers will use their own preferred data reduction package if they wish to work interactively work on their data. The rest of this document summarizes and accounts for the operational differences between the pipeline and existing packages.
This is crucial. Everything else about the package is clear once this is grasped. This is not a reduction package like CGS4DR; it is a reduction black box which knows the incoming data types (by their headers) and transparently applies a reduction recipe to them. There is nothing preventing you from running three simultaneous instances of the pipeline, for example to (i) reduce the incoming data in real time, (ii) re-reduce a previous group of files using a different reduction recipe and (iii) reduce and file a single previous observation as a dark. You do this by running three versions of oracdr, using the command-line switches to alter their behavior (recipe, start and end observation numbers to process, graphics options, etc.). Each instance of the pipeline will go through the required files (existing ones or files just arriving on disk as specified on the command line) and reduce them. Once its remit of reduction is complete, it will exit.
The behavior of ORAC-DR is entirely controlled by the command line options entered at startup. From that point on, the system either takes its reduction recipe instructions from the file headers (this is the default) or uses a hardwired recipe given on the command line itself. The recipe is, in fact, the only allowed parameter on the command line - all the rest are options. Once you start an instance of oracdr up, there is no further control over it; this is a considerable change from the situation with CGS4DR, for example, where the same package remains up once you start it, and changes are made within the package. Corollary: if the pipeline fails to find a required calibration frame, for example, the only logical thing for it to do is exit cleanly, telling you why it did so. There is no control from within the pipeline. Note that once the full ORAC system is available, there will be plenty of pre-checking that your calibration frames will indeed exist and be appropriate. Until that point, the behavior of the system is logical if you understand the underlying philosophy and do not expect to be able to control the pipeline in real time.