The Advanced Camera for Surveys (ACS) is a new CCD instrument
installed in the Hubble Space Telescope (HST) during Servicing
Mission 3B. It includes a High Resolution Camera (0.025 arcsec/
pixel) with a selectable coronagraphic mode. Because it was added
after construction began on the camera, this classical Lyot
coronagraph must operate on the uncorrected, spherically aberrated
beam from HST. The occulting spot is placed at the circle of least
confusion, requiring relatively large spot diameters of 1.8 and
3.0 arcseconds. The Lyot stop is placed at the correcting
mirror that compensates for spherical aberration. Despite this
nonoptimal configuration, the diffraction pattern is expected
to be reduced by a factor of 5x-10x, bringing it below the
level of light scattered by the mid-spatial-frequency errors
in the HST optics. The coronagraph will provide for high-
resolution, high-contrast imaging over a large wavelength
range (200-1000 nm). The on-orbit performance and recent science
results are described.
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