John McGraw, Ph.D. - US grants

The Charge-Coupled Device (CCD)/Transit Instrument (CTI) surveys nightly about 15 square degrees of the sky in two optical colors to a limiting magnitude of visual brightness greater than 21 signal to noise S/N greater than 5). Each night the V magnitude is measured as well as one of Ultraviolet (U), Blue (B), Red (R), or Infrared (I). The colors will be selected to optimize S/N relative to the sky brightness. An infrared CCD will provide nightly K magnitudes for about four square degrees of the same strip. The observing program of CTI is to remain on the same strip of sky for several years, intensively observing the same 45 square degrees per year for several years (12 square degrees in the IR), both to monitor the brightness changes of the objects in the strip and to acquire deeper images by adding data from multiple nights. Data derived from this instrument will be used to address a variety of astronomical problems ranging from discovery of nearby stars to measurement of variability of distant quasars. Three scientific programs will be addressed by project astronomers. These programs are : 1) the discovery and monitoring of quasars on the basis of variability and color, 2) a determination of the supernovae production rate, and 3) discovery of supernovae for use as distance indicators.

AST-0421087 -- McGraw, University of New Mexico

A compact, rugged, eye safe, low-cost lidar will be developed, specifically to measure atmospheric extinction at the New Mexico sky survey site at McDonald Observatory in West Texas to support the scientific programs of the CCD/Transit Instrument (CTI). The observing program of the CTI will accomplish a precise time-domain imaging photometric survey in multiple optical and near-infrared bandpasses of approximately 1% of the sky per night. The lidar data will enable more precise photometry by providing real-time measurements of the amount of atmopsheric extinction as well as its cause, i.e. low-lying aerosols, dust or smoke in the free troposphere, or high cirrus.

Dr. McGraw and his collaborators will undertake an observational and instrumental effort to create a series of standard stars whose flux (energy received per second) is accurately calibrated. The project will include modifications to the Astronomical Lidar for Extinction, an NSF-funded effort to use light scattering from lasers to measure the transmission properties of the atmosphere. The main goals of the project are to implement the new instrumentation to measure the extinction in the atmosphere to accuracies below 1% (including variations with time, direction, and wavelength), and to obtain simultaneous measurements of candidate standard stars with a spectrophotometric telescope calibrated with standard photodiodes.

The techniques and instruments developed by this project would have a broad impact to the community, particularly if the instrumentation is duplicated and adopted by other observatories. This would increase the number of useful nights at major facilities by providing better atmospheric corrections, and would address calibration issues for projects such as surveys for dark energy. There will also be an extensive effort in workforce development, especially by including undergraduates in several different phases of the effort. This would target students at the University of New Mexico, a major Hispanic-serving institution.