The system computer has two principal roles as part of the data-acquisition system:
On completion of an exposure, the data is normally transferred from the DMS to the system computer, via a DR-11W interface. The header information associated with that data will have been collected by the system computer, either during the exposure, or on completion of the exposure. Data and headers are then merged into a datafile on the system computer disk. The datafile is in HDS NDF format, the header information being stored in the standard FITS extension to this format. Finally, two copies of the data are written to tape; a FITS format tape for the La Palma archive, and either a FITS tape or a VAX backup tape for the observer.
The system computer is networked to various data reduction computers (currently a VAX 3500 plus several VAXstations). Data can be copied across to these machines for immediate processing.