Orthogonal transfer arrays for wide-field adaptive imaging
The orthogonal transfer array (OTA) is a novel charge-coupled device (CCD) imager based on the orthogonal-transfer CCD (OTCCD). The OTCCD, in turn, is a device capable of charge transfer in all directions and has been developed for adaptive imaging in ground-based astronomy. By using a bright guide star as a beacon, the OTCCD can correct for wavefront tilt due to atmospheric effects as well as compensation for telescope shake, which in turn enhances the resolution and SNR. However, for wide field-of-view imaging the atmospheric wavefront distortions decorrelate over distances more than a few 10's of arcmin and hence an array of independently driven OTCCDs is required. To resolve this issue we developed the OTA, which consists of a two-dimensional array of OTCCDs combined with addressing and control logic to enable independent clocking of each OTCCD. This device enables spatially varying electronic tip-tilt correction and was developed for the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) program at the University of Hawaii Institute for Astronomy (UH/IfA)