How do the low-response regions of the FUV affect off-center objects?
The FUV sensitivity drops off quickly in two directions away from the center. This drop is large enough (about 30% less response) to significantly effect the actual S/N of an off-center object. See FUV flat field image and compare NUV flat field image. However, the selection of an optimal spacecraft roll angle in phase 2 could mitigate this effect for a given object, but optimal rolls are not always be available.
