Maintained by W-W
The "retina" of a present-day astronomical camera is a large electronic chip. Chips for detecting visible light are made of silicon; those for detecting infrared radiation are made of semiconductors such as indium antimonide (InSb) or mercury cadmium telluride (HgCdTe). In the last few years there have seen enormous improvements in both the sensitivities of these detector chips, and in the number of pixels they contain.
Development of chips requires cooperation between commercial electro-optical companies and the astronomers and engineers at the Institute for Astronomy. While the chips themselves are produced on the U.S. mainland, the tasks of adapting them for use in astronomical situations and maximizing their sensitivity to faint light sources are done at the University of Hawaii.
Klaus Hodapp has been working with the Rockwell Science Center to develop a 1-2.5 micron array for use in the spectrograph being built for the 3.67-meter AEOS telescope project on Haleakala, Maui. The device is named the HgCdTe Astronomical Wide Area Infrared Imager (HAWAII). Science-grade 1024 x 1024 pixel devices have been installed in the UH instruments QUIRC and KSPEC , while the AEOS instrument itself will employ the HAWAII-II 2048 x 2048 pixel arrays.
Don Hall looks farther into the future with his NASA-funded program to characterize ultra low background Mercury-Cadmium-Telluride (HgCdTe) detectors for use in the James Webb Space Telescope--NASA's planned successor to the Hubble Space Telescope.
Four of the 2048 x 2048 pixel chips, built in partnership with Rockwell Scientific Company, have been built into an infrared camera (called ULBCam) for the UH 2.2-m telescope, making this relatively small telescope the most powerful in the world for wide-field infrared imaging.
John Tonryand Gerry Luppino are collaborating with colleagues at Lincoln Laboratories to develop and exploit "orthogonal transfer" CCDs (OTCCDs). These special arrays are designed so that the astronomical image that is being exposed on the array can be electronically shifted to-and-fro to compensate for random motions induced by Earth's atmosphere. Moving an image on a CCD chip can be done much more quickly than moving one of the mirrors of a telescope, as in a conventional adaptive optics system. This detector is built in a modular way that will allow scaling to much larger arrays at low cost.
Each of the four cameras that are being built for Pan-STARRS will contain 64 orthogonal transfer arrays, each of which contains 64 OTCCDs that are 512 x 512 pixels in size.