Charge-Coupled Device (CCD)/Transit Instrument (CTI) Deep Photometric And Polarimetric Survey-A Progress Report

AbstractWe have previously reported on the conceptual design and predicted performance of a newtype of dedicated astronomical telescope to be used fo a deep photometric survey for ga-lactic and extragalactic variability and polarization. Data derived from this survey willbe useful for a wide variety of astronomical investigations including the definition of acomplete sample of QSOs, based on their variability and nonstellar colors, the detection ofsupernovae on the rising branch of their light curves, and the determination of the super-nova production rate as a function of galaxy color, morphology and redshift.The telescope we are producing to accomplish this survey is a transit instrument. It will incorporate a 1.8 m primary mirror of very high quality, fabricated as part of theprogram to develop the Space Telescope mirror technology, and, as its detectors, two RCACCDs (512 x 320 x 30 micron pixels) used in the time -delay and integration (TDI) mode. Bymeans of a dichroic beamsplitter the two CCDs view the same region of the sky, subtendingabout 8.2 arcminutes in declination. The effective integration time on the sky using thistechnique is about one minute, resulting in a faint limiting magnitude of about 22 pernight. The data from the digitized strip of sky is recorded and analyzed in real -time forspecific events such as supernovae.The CCD /transit technique has been demonstrated using the Steward Observatory (SO) 2.3 mtelescope with the drive switched off. The results of this demonstration are shown anddiscussed. We report on progress in all aspects of the CTI development including the de-sign of the transit telescope, which is optimized for wide -field, seeing -limited imaging.In particular, we describe a two- mirror field corrector system which realizes the potentialimage quality of the high precision primary mirror over a wide field and over the widespectral bandpass of the CCDs.IntroductionEvery clear night the CTI will survey about 20 square degrees of the sky to a faintmagnitude limit of 22. Data will be reduced in real -time, thus ensuring fast, easy accessto specific results. Because the survey is random in the sense that objects are not selec-ted - everything seen by the telescope is measured - and there is a definite, faint limitingmagnitude, the results will be statistically valid. The survey is designed to automaticallysearch for brightness changes and measure colors and polarization in stars and galaxies.The specific programs we shall carry out include the definition to faint limiting magni-tude of a statistically complete sample of QSOs, the detection of supernovae on the risingbranch of their light curves, and the determination of the supernova production rate as afunction of galaxy color, morphology and (with spectroscopic data) redshift. It is ourintention to leave the telescope fixed, scanning the same strip of sky for a minimum of twoyears. This will enable us to study fairly long -term as well as short -term variability,and to build up very deep co -added images in all the color bands.The basic concepts of the telescope we are building to carry out this survey are ex-tremely simple. The telescope is a non -moving transit instrument which will be locatedon Kitt Peak Mountain. Two CCDs, utilizing optical bandpasses defined by a dichroicbeamsplitter and filters (or when polarization is to be measured, a polarizing beamsplitter