The All Sky Infrared Visible Analyzer (ASIVA) is an instrument principally designed to characterize sky con-
ditions for purposes of improving ground-based astronomical observational performance. The ASIVA's primary
functionality is to provide radiometrically calibrated imagery across the entire sky over the mid-infrared (IR)
spectrum (8-13 μm). Calibration procedures have been developed for purposes of quantifying the photometric
quality of the sky. These data products are used to provide the STELLA scheduler with real-time measured
conditions of the sky/clouds, including thin cirrus to better optimize observing strategy. We describe how this
can be used in the denition of the observing programs to make best use of the telescope time. Additional
research is underway to correlate infrared spectral radiance with visible-spectrum extinction.
The LSST project has updated the all-sky IR camera that was installed on Cerro Pachón in Chile to continue its
investigations in cloud monitoring and quantifying photometric conditions. The objective is to provide the survey
scheduler with real-time measured conditions of the sky/clouds, including high cirrus to better optimize the observing
strategy. This paper describes the changes done to improve the detection performance of the first generation system and
presents comparison results of visible and IR images.
The LSST project has acquired an all sky IR camera and started to investigate its effectiveness in cloud monitoring. The
IR camera has a 180-degree field of view. The camera uses six filters in the 8-12 micron atmospheric window and has a
built in black body reference and visible all sky camera for additional diagnostics. The camera is installed and in nightly
use on Cerro Pachon in Chile, between the SOAR and Gemini South telescopes. This paper describes the measurements
made to date in comparison to the SOAR visible All Sky Camera (SASCA) and other observed atmospheric throughput.
The objective for these tests is to find an IR camera design to provide the survey scheduler with real-time measured
conditions of clouds, including high cirrus to better optimize the observing strategy.
The University of Denver is now completing construction of a mid-infrared imaging polarimeter dubbed TNTCAM Mark II. The instrument will be the only one of its kind capable of attaining polarimetric accuracy of 0.2 % across the 5 -- 25 micron spectral interval. This sensitivity is only attainable by cooling the transmissive polarizing optics to liquid helium (LHe) temperatures. A major technical challenge in the design of this instrument has been finding a way to modulate the polarization signature of the incoming beam at a rate sufficient to combat the degrading effects of the atmosphere. Our group has chosen to quickly rotate a half-waveplate situated on the cold (i.e. 4 degrees Kelvin) work-surface. The waveplate is rotated between two fixed positions separated by 45 degrees at a rate of 1 Hz to obtain one of the two Stoke's parameters required to measure linear polarization. The waveplate is then offset by 22.5 degrees and then rotated again at 1 Hz between two positions separated by 45 degrees to obtain the other Stoke's parameter. In addition to rotating the waveplate, the waveplate itself must be moved out of the beam during normal imaging applications. The camera can contribute to the understanding of YSOs and evolved stars, obtaining high resolution mid-IR observations of dusty environments immediately surrounding these objects. In imaging mode mosaics of extended objects can be made in 2'x2' sub-fields. In polarimetry mode, B-fields in YSOs can be probed by dust emission from hot cores, incidentally constraining grain alignment scenarios in young stellar environments. In this paper we present the design and the results of our moving optical componenets susbsytem. Five cryo-stepper motors drive these mechanisms. This instrument is being developed under NSF grant AST-9724506 and is slated for community access in January 2000.
We present design considerations for a mid-IR imaging polarimeter, TNTCAM II. Using a 256 by 256 Si:As BIB array, the camera will be unparalleled as an polarimeter/imager by any instrument currently in use at these wavelengths. Thanks to NSF support, access by the general astronomical community will be arranged. In polarimetry mode, TNTCAM II will be sensitive to linear polarizations as small as 0.2 percent. Polarized emission from cosmic sources will be modulated at a frequency high enough to remove atmospheric and system noise fluctuations. Dewar design and the optical system are discussed, including CCD assisted digital shift and ad tip- tilt correction and use of a rotating entrance window assembly allowing on-the-fly f-ratio adjustment and optimal throughput across the entire 5-25 micrometers band. The camera can contribute to the understanding of YSOs and evolved stars, obtaining high resolution mid-IR observations of dusty environments immediately surrounding these objects. In imaging mode mosaics of extended objects can be made in 2' by 2' sub-fields. In polarimetry mode, B-fields in YSOs can be probed by dust emission from hot cores, incidentally constraining grain alignment scenarios in young stellar environments.
We present a brief overview of the design and construction of two grating infrared spectrometer, a new 2D array, dual grating spectrometer for the 7.0 to 13.8 micron region, built at the University of Denver (DU). This instrument has been designed to fulfill specific scientific goals in astronomy while utilizing the array to its fullest extent. The instrument uses diamond-turned aluminum optics to allow warm optical alignment and eliminate differential contraction of the optics while operating at cryogenic temperatures. Two gratings are used in the optical design to provide a resolution of about 800. The entire assembly is cooled with a Gifford-McMahon refrigerator so that it may later be adapted for use during remote observing. The array is a Rockwell 128 by 128 Si:As BIB hybrid focal plane array sensitive from optical to 26 microns. The electronics package and software for readout were developed by Wallace Instruments and are already in use on our TNTCAM at DU. 'First light' is scheduled for late summer 1996.