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Primary Quantities Measured with System Typical |
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There are several applications for which these instruments have been used. In the early days of its use, satellite tracks were superimposed on the images. The sponsor was able to assess the performance of trackers by determining the locations along the tracks where clouds or enhanced background radiance might interfere with tracker performance. The instruments have been used alert the sponsors when the cloud fields would render expensive laser tests useless due to clouds (which could not be detected visibly). At times, detection of the quickly changing cloud field enabled sponsors to detect and respond to windows of opportunity for testing. The WSIs have also been used in a variety of research applications related to cloud distribution and persistence, and radiance distribution.
They could be adapted for many other applications. For example, if a test site or observatory is interested in imaging any of several stars with their existing systems, they could assess which directions are most cloud-free, and provide alarms for encroaching clouds or crater fog. The images can be processed to evaluate specific regions or directions, to assess the clouds, as well as absolute sky radiance. The ability to assess the earth-to-space beam transmittance distribution (in all directions) at night is also under development. For example, if a site is acquiring spectral radiometric measurements of specific stars, the WSI could be used to assess the changing magnitude of the background radiance (due to moonlight) and its possible impact. For tracking stations, the WSIs could be adapted to assess which of several tracks is the most productive to follow.
Although designed as research instruments, they are quite robust – we have operating units in the arctic, tropics, and desert. They operate under all conditions (starlight, moonlight, and sunlight), with a solar/lunar shade to provide optimum imaging. They are fully automated, and can be adapted for a number of purposes. We have developed WSI units under funding from Air Force, Army, Navy, DOE, and the Deutscher Wetterdienst (German weather service). Customized versions of the instruments having the capabilities required by a specific site have been developed as needed. We normally remain involved with the instruments after their deployment, analyzing the data for the sponsors’ applications, and developing new capabilities specific to their needs.
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by the Marine Physical Laboratory, SIO.
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