We discuss the design and development of Ranicon detectors for optical photon counting imaging on ground-based telescopes. The significant factors which determine the performance of these detectors are found to be the proximity focusing stage, the microchannel-plate stack (MCP), and the signal processing electronics. For applications in optical astronomy, the low photon counting efficiency typically found with optical MCP-based detectors, due to ion barrier films, presents an additional consideration. We review the performance of each stage of the Ranicon detector and the techniques for achieving optimal performance. A new approach to the signal processing electronics reduces nonlinearity, while achieving increased processing speeds and a position error corresponding to <21 μm FWHM. A significant improvement in detector performance is achieved with an advanced Ranicon incorporating a reduced proximity focusing gap and an unfilmed input plate in the MCP stack. The theoretical spatial resolution of both standard and advanced Ranicon designs is derived and compared to the experimentally determined values. For the advanced Ranicon, this spatial resolution is shown to be typically 40 μm FWHM at ∼650 nm. The point spread function of the Ranicon system is shown to be stationary over the active imaging area, principally due to the removal of nonlinearities and noise sources from the signal processing electronics.
The Advanced Camera for the Hubble Space Telescope will have three cameras. The first, the Wide Field Camera (WFC), will be a high throughput (45% at 700 nm, including the HST optical telescope assembly (OTA)), wide field (200"x204"), optical and I-band camera that is half critically sampled at 500 nm. The second, the High Resolution Camera (HRC), is critically sampled at 500 nm, and has a 26"x29" field of view and 25% throughput at 600 nm. The HRC optical path will include a coronagraph which will improve the HST contrast near bright objects by a factor of -10. The third camera is a far ultraviolet, Solar-Blind Camera (SBC) that has a relatively high throughput (6% at 121.6 nm) over a 26"x29" field of view. The Advanced Camera for Surveys (ACS) will increase HST's capability for surveys and discovery by at least a factor of ten. 184 /SPIE Vol. 2807 0-8194-2195-2196/$600 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/22/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx 186/SPIE Vol. 2807 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/22/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspxAs in the WFC, on-orbit focus and pupil alignment adjustment is required. This is accomplished by mounting the Ml mirror on a "Wally Wobbler", a novel mechanism which provides tip, tilt, and focus adjustment. This mechanism, designed by Wallace Meyers at the Ball Aerospace Corporation, incorporates three nested cylinders, driven by two motors (two degrees of freedom), 190/SPIE Vol. 2807 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/22/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx
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