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Pointing Error Analysis Tool - Concepts from Optics PDF Print E-mail
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Pointing Error Analysis Tool
Pointing Error Definitions
Concepts from Optics
Standard Pointing Error Metrics
Computational Techniques for Evaluating the Pointing Error Metrics
Why Not Use the Peak Stability or Other Metric?
Pointing Error Analysis
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Concepts from Optics

The optical quality of an imaging system is limited partly by the quality of its optics. The point spread function (PSF) describes how a column of light is spread out after passing through the optics. The PSF is shown in the first figure below. The bright central region is called the Airy Disc. A cross section of the Airy Disc is shown in the second figure. This function can be approximated as a Gaussian G(x, σ2psf). The effect of jitter motion on image quality can be determined by how it affects the PSF. Line-of-sight jitter motion can generally be modeled by as a Gaussian random error with variance σ2j. The effective PSF is given by the convolution of the Gaussian PSF and the Gaussian jitter, which is simply G(x, σ2psf + σ2j). In effect, the jitter motion widens the PSF. The jitter affects the image only during an exposure time of T seconds, so the jitter variance is computed over a window of T seconds.

Point Spread Function Airy function and Gaussian approximation

Point Spread Function with Airy DiscAiry function and Gaussian approximation