Overview of Current Work

The late 1990’s and early 2000’s have been spent on developing Whole Sky Imagers and their capabilities in several areas A new Daytime WSI was developed for Germany's weather service, Deutsche Wetterdienst. This instrument provides much higher image quality than the original Day WSI’s, extends the sensitivity into the NIR, and includes calibrated radiances. The instrument includes additional spectral bands, as well as two polarizers in the filter changer. It includes a 12 bit digital camera, as well as a fisheye lens and solar/lunar occultor.

The Day/Night WSI’s have been further developed in several regards, including:

Further instrument hardening, including better engineering of the occultor and the environmental housing
Developing software and hardware for real-time processing of the cloud algorithms
Developing a more simplified version of the real-time processing WSI which may be remotely sited from the user.

A new miniaturized version of the imager has been developed for downward looking applications from a UAV. Two of these instruments have been developed for Sandia National Labs, and the ARM UAV program. One will sense wavelengths near 650 nm in the red, and the other will sense wavelengths near 1600 nm in the NIR. Both will be calibrated to provide the absolute radiance distribution of the lower hemisphere below the aircraft.

Analysis work during this period has included development of a new night-time cloud algorithm based on the detection of stars. Two versions of this algorithm are in operation; one developed from MPL’s ideas by our ARM sponsors, is being used on the ARM archival data, as noted earlier. A second version developed at MPL is being used to provide the real time algorithm results with military instruments. This version of the algorithm is also under further development, with the goal of extracting the spatial distribution of the atmospheric beam transmittance at night. Additional work has included analysis of Cloud Free Line of Site statistics from the Day WSI database, as well as the persistence of these parameters.

Additional engineering work currently includes the development of the Field Calibration Device, which includes programs to enable less experienced personnel to interactively acquire the calibration data and interactively process the data. A new solar occultor which will mask much smaller portions of the sky is under development. As always, analysis of new techniques for meeting the needs of the atmospheric research community are under way.

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