What is the spatial coverage of CDS?
The internal scan mirror and slit movement of CDS allow CDS rasters to cover a maximum area of 4′ square within a single raster. The E-W coverage is created by the scan mirror which can move in steps of 2.03″ (normally assumed to be 2″). Movement can only be in one direction from West to East. In NIS the N-S coverage is usually provided by the long slit (normal slits are 2″x240″ or 4″x240″). For GIS the N-S dimension is scanned by moving one of the small square slits which can move in steps of 1.01″ (normally assumed to be 1″!). Because of readout problems with the slit movement encoder, there are restrictions on the movement of the GIS slits when rastering in the North-South direction. The planning software has been updated so that the corrections to handle this problem are automatically calculated and the user should not see any effect or need to take any specific action. GIS rasters can once again be planned as normal. Planners should continue to take note of the pointing offsets be
