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The aim of this section is to provide an overview of the scanning components which comprise SuperCOSMOS, so that the reader may appreciate how the various sub-systems are related, and so that the reasons behind design decisions may be understood.

The principle behind SuperCOSMOS is very simple: light is shone through the photographic emulsion being measured, and the amount of transmitted light is measured by a CCD detector. The analogue output from the CCD is digitised and transferred to a transputer system where initial real-time data-processing is carried out, and then on to further post-processing stages on transputers and workstations. A scan of a plate is constructed by moving the plate through the light path: the physical movement is carried out by the Leitz PMM 654 coordinate measuring machine on which the plate is mounted. In practice, this process has to be carried out with high accuracy and speed.

Mon Aug 5 15:56:21 BST 1996