New Filtering and Regulation Techniques With Applications to 
Airborne Pointing Systems, 03-9167

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Principal Investigator
Monty J. Smith

Inclusive Dates: 10/01/99 - Current

Background - With recent advances in digital signal processors, new abstract approaches to advanced filtering and noise cancellation methodologies can be readily implemented. High-precision gimbaled pointing and synthetic aperture radar for airborne systems require extremely accurate alignment in an electronically noisy environment. The existing technology for the development of noise cancellation algorithms is commonly based on linear systems theory. Serious limitations in system performance and robustness occur due to the inherent structure required of the linear compensation/filter synthesized. SwRI investigators have recently synthesized new methodologies that generalize the existing filtering and closed-loop compensation techniques using nonlinear feedback filtering.

Approach - This project involves completion of theoretical results and the development of hardware for implementation of these new filtering techniques to the pointing improvement of an astronomical telescope. The experiment (in hardware) involves regulating or filtering noise using this new optimal approach on a digital signal processor to enhance the alignment characteristics of an astronomical telescope. This method is consistent with current NASA programs with requirements to control the pointing of astronomical telescopes aboard balloon-borne gondola platforms. Such applications require the use of an active pointing and tracking system that maintains the astronomical target within the field-of-view of the telescope to well within the spatial resolution of the instrument. One prime application for this new filtering approach is a coronagraphic telescope designed to image the solar corona surrounding the sun, or the lunar atmosphere surrounding the moon at mid-ultraviolet and visible wavelengths aboard a balloon-borne platform at altitudes exceeding 100,000 feet (30,480 meters). The spatial resolution of this instrument is on the order of 30 to 60 arcseconds. Hence, the pointing stability of the instrument must be within ±10 arcseconds or better to maintain the spatial resolution in the presence of random attitude perturbations of the balloon-borne gondola.

Accomplishments - The gimbal and telescope assemblies are under construction with appropriate electronics to sense angle measurements and alignment characteristics. Algorithms for implementing this new optimal filtering approach have been realized using the C language preferred by industry. A commercially available floating point processor with capabilities to compute 1,000 million floating-point operations per second is inclusive with a board currently under analysis for implementing this new filtering algorithm. Initial tests have been performed successfully using pure open-loop analysis for the development of various signal waveforms from the processor.

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