PROCEEDINGS ARTICLE | August 28, 1998
Proc. SPIE. 3356, Space Telescopes and Instruments V
KEYWORDS: Optical filters, Mirrors, Prisms, Silica, Cameras, Wavefronts, CCD cameras, Refraction, Image filtering, Transmittance
The Hubble Space Telescope (HST) advanced camera for surveys (ACS) employs a wide variety of spectral filtration components including narrow band, medium band, wide band, and far UV (FUV) long pass filters, spatially-variable filters, VIS/IR polarizers, NUV polarizers, FUV prisms, and a grism. These components are spread across ACS's wide field, high resolution, and solar blind channels which provide diffraction-limited imaging of astronomical targets using aberration-correcting optics which remove most aberrations form HST's optical telescope assembly. In order for ACS to be truly advanced, these filters must push the state-of-the-art in performance in a number of key areas at the same time. Important requirements which these filters must meet include outstanding transmitted wavefront, high transmittance, uniform transmittance across each filter, spectrally structure-free bandpasses, exceptionally high out of band rejection, and a high degree of parfocality. These constitute a very stringent set of requirements indeed, especially for filters which are up to 90 mm in diameter. The development of unique optical metrology stations used to demonstrate that each ACS filter will meet its design specifications is discussed. Of particular note are specially-designed spectral transmissometers and interferometers.
