Why are gaps seen in the HRI detector maps?
The image of the HRI in detctor coordinates shows the photon positions in raw electron read-out coordinates. This is how the data is initially recorded. The data then must be de-gapped and aspect- corrected. In the raw coordinate system, the HRI is highly nonlinear. The gaps actually have no spatial width. De-gapping simply maps the detector coordinates into a linear coordinate system. The aspect solution then converts to RA/Dec.
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