Technical description

The pupil-imaging mode is set up by inserting the double-lens set in the region near i1 and p1. One of the two lenses is mounted in the special lens wheel located between the filter wheel and the slit wheel, and the second lens of the pair is mounted in the slit wheel. This mode permits examination of the telescope pupil plane to monitor the thermal environment there and to confirm that the Lyot stops and coronagraphic masks are properly centered and oriented.