AuthorNagler, Michael N.
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PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractThe design of BOLTS (Broad Area Lightning Telescope Sensor) is presented. This sensor will provide full-time (day/night) coverage of the continental U.S. from a geosynchronous orbit. The average ground resolution will be 8 km and the system will be able to detect ≃ 10⁷ watt strokes during nighttime and ≃ 4 x 10⁷ watt strokes during daytime with a probability of detection of 0.9. We present the system's requirements and projected performance, together with the design rationale. Contrast enhancement is achieved using a narrow band interference filter deposited on a curved surface inside the F/2.5, 101.7 mm optical system. Deposition of the interference layers on the curved surface reduce the passband wandering caused by off-axis bundles. The focal plane constitutes an 800 x 800 element virtual phase CCD array with a multiple outputs option. The central 800 x 400 elements are used for imaging while the outer 2x (800 x 200) elements serve as buffer memory for one frame storage. An additional 2x (800 x 200) array serves for storing a second frame. Signal detection is achieved via a frame-to-frame subtraction algorithm that is hardware implemented immediately following the CCD arrays. An integration time of 5 msec is used, which stems from SNR optimization requirements and from the fact that lightning strokes occur randomly in time and space. The data obtained after frame-to-frame subtraction is subjected to a threshold test and the resulting positive events are digitized and stored in an on-board digital memory using 48 bits/event. Each record contains intensity information over a dynamic range of 4000, location information and time of occurrence information. A prototype instrument built to perform measurements from aboard a U-2 plane is described. The purpose of this instrument is to refine some of the lightning data used in defining the system's parameters. A short discussion about the changes required to expand the design to either a global coverage instrument or a high resolution, smaller field instrument is presented.
Degree ProgramGraduate College