This camera has 0.075 arcsec pixels, covering a 19.2 x 19.2 arcsec region of the sky. The coronographic spot imaged onto the focal plane provides a circular occulted region 0.3 arcsec in radius. At this radius, in an idealized Point Spread Function, a natural break occurs in the encircled energy profile at 1.6 microns with 93 percent of the energy in the PSF being enclosed. Beyond, the encircled energy profile flattens out toward larger radii. The Camera 2 coronograph comprises two elements.
Initial indications are that the coronograph meets or exceeds expectations.
Coronographic Acquisitions Coronographic imaging requires an acquisition sequence at the beginning of the observation to center the target onto the occulting spot since the size of the occulting spot is smaller than typical HST blind-pointing errors. The procedure for a coronographic observation is to first acquire the target on the NIC2-ACQ aperture using an onboard, reuse target offset, or interactive acquisition. This is illustrated in Figure 5.1 which shows a schematic representation of the Camera 2 acquisition aperture. The telescope is pointed so that the target nominally appears at the aperture NIC2-ACQ which is located in a 128  x  128 logical acquisition aperture. The acquisition software, analyzes this aperture, locates the center of the target, and offsets the telescope so that the target is placed behind the occulting spot.