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1

Reconstruction of Images with Poisson Noise

Sylwester J., Sylwester B.

Acta Astronomica

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1999

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Vol. 49, No. 2

189--199

EN

This paper addresses quantitatively the problem of influence of statistical uncertainties embedded in the recorded image on uncertainties of the reconstructed image. In the analysis we use iterative maximum likelihood algorithm Andril (described by Sylwester and Sylwester 1998) developed for massive deconvolution of flare images obtained by the Soft X-ray Telescope (SXT) on Yohkoh. We illustrate the "ill-conditioned" nature of the image reconstruction problem and suggest the ways to reduce, at least partly, propagation of noise to the reconstructed image.

2

Flaring Structures Observed in Deconvolved SXT Images

Sylwester B., Sylwester J.

Acta Astronomica

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1999

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Vol. 49, No. 1

85--102

EN

We present and discuss evolution of flaring structures morphology as observed in deconvolved soft X-ray images. The X-ray images have been obtained using the Soft X-ray Telescope (SXT) on Yohkoh. The deconvolution has been made using the iterative maximum likelihood algorithm Andril. In the reconstructed images it is possible to study the position of individual fine structures for the first time with the resolution superior to the SXT pixel size. We show example of the analysis of deconvolved images for one disc flare on July 11, 1992 at 15:25 UT. Corresponding figures and animations for two other flares are available at the address www.cbk.pan.wroc.pl and at the Acta Astronomica Archive (see second cover page for details). These flares occurred on November 19, 1991 and on January 13, 1992 and have been located near/at the limb. We conclude about the differences of physical conditions of the flaring plasma confined in compact bright regions (kernels) located in the footpoint and summit areas.

3

ANDRIL - Maximum Likelihood Algorithm for Deconvolution of SXT Images

Sylwester J., Sylwester B.

Acta Astronomica

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1998

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Vol. 48, No. 3

519--545

EN

We present an iterative deconvolution algorithm called ANDRIL devoted for advanced processing of images obtained by the Soft X-ray Telescope (SXT) on Yohkoh. The algorithm is based on maximum likelihood approach. We introduced several modifications to this algorithm in order to optimize its properties. The goal of the algorithm is to remove numerically the image blurring due to the instrument point spread function (PSF) and increase the image resolution. The application of the algorithm allows to resolve soft X-ray structures in the SXT images on the angular scales down to 1 arcsec. Presented algorithm has been recently used for analysis of detailed morphology and physical conditions in the plasma of flaring structures.