Accession Number : ADA221227


Title :   Super-Diffraction Limited Measurements through the Turbulent Atmosphere by Speckle Interferometry


Descriptive Note : Final technical rept. 15 May 1986-14 Nov 1989


Corporate Author : GEORGIA STATE UNIV ATLANTA CENTER FOR HIGH ANGULAR RESOLUTION ASTRONOMY


Personal Author(s) : McAlister, Harold A


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a221227.pdf


Report Date : 22 Feb 1990


Pagination or Media Count : 220


Abstract : Speckle interferometric methods provide a means for reconstructing diffraction limited images from atmospherically blurred image data obtained in snapshots with exposure times shorter than the atmospheric redistribution time, typically shorter than 20 milliseconds. Several areas of research were emphasized: (1) Speckle Photometry - The extraction of the differential brightness and color of the components of close binary stars has always been a fundamental limit to the usefulness of these objects to stellar astrophysics. Simple and fast methods were developed and applied to actual data which enable the measurement of these parameters for large numbers of stars. Newly developed algorithms include a directed vector-autocorrelation (DVA) technique for eliminating the 180 deg quadrant ambiguity inherent in speckle interferometric measurements of the astrometry of binary stars. DVA is a simple extension of normal vector-autocorrelation and requires orders of magnitude less computing time that standard image reconstruction methods when applied to binary stars. The second new algorithm is known as the fork method and provides a means for a statistically based determination of the intensity ratio of a binary at any selected wavelength, thereby providing color information through the comparison of any two wavelengths. (2) Super Diffraction-Limited Detection - The very high accuracy of speckle astrometry provides a leveraging method for detecting close companions whose spatial separations are far less than the diffraction limit. In principle, this accuracy is sufficient to detect brown dwarf stars and high-mass plants in orbit around one component of a wide binary system.


Descriptors :   *BINARY STARS , *PHOTOGRAPHIC ANALYSIS , *SPECULAR REFLECTION , *IMAGE PROCESSING , RATIOS , DETECTION , HIGH RATE , EXPOSURE(GENERAL) , INTENSITY , ACCURACY , TURBULENCE , BRIGHTNESS , INTERFEROMETRY , SPHERICAL ASTRONOMY , LIMITATIONS , COLORS , STANDARDIZATION , SEPARATION , DETERMINATION , ATMOSPHERES , STARS , PHOTOMETRY , DWARF STARS , ASTROPHYSICS , METHODOLOGY , MEASUREMENT , SPATIAL DISTRIBUTION , ALGORITHMS , DIFFRACTION


Subject Categories : Astronomy
      Photography


Distribution Statement : APPROVED FOR PUBLIC RELEASE