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General description

The data-acquisition system can (somewhat arbitrarily) be divided into the following components:

• The detectors themselves. Two types of detectors are available; various CCDs, and the IPCS-2 photon counting system. Each detector has an associated local controller.
• The Detector Memory System (DMS). Immediately after an exposure, the data from all detectors appears in memory in the DMS. Images obtained with CCD detectors are read out into the DMS at the end of an exposure. Photon counts from the IPCS--2 are continually transferred to the DMS during an exposure, where they are built up into an image ( c.f. the External Memory for IPCS-1).

  The DMS provides some basic data-analysis facilities; however, these facilities will not be fully supported once the SPARCstation data-evaluation system comes on-line (see below).

• The SPARCstation analysis-system. Images captured in the DMS can be rapidly transferred to this SPARCstation, where they can be inspected using IRAF.
• The system computer. On completion of an exposure, the data is transferred to a data disk on the system computer, where it is merged with header information, and then archived. The data can also be copied from the system computer to one of several data-reduction computers.

These components of the system are described more fully in the subsequent sections. The flow of data between the different parts of the system is illustrated in Figure 1.1.

It should be noted that we have attempted to describe the data acquisition system as it currently is, not in its final planned form. It is expected that in the long term, the SPARCstation will take on much of the functionality of the DMS and that data will be archived through the SPARCstation rather than through the system computer.