Project Purposes:Devconvolution of the core part of SXT point spread function (PSF) from recent solar flare images taken in thick aluminum filter.Comparison of deconvolved PSF with formerly on-ground determined PSF cores (Martens, Acton, Lemen, 1995. ) MethodThe PSF is being restored from flare images by Blind Iterative Deconvolution (BID) method (Ayers, Dainty, 1988), adapted to deal with SXT images. The above method allows for restoring PSF and deblurring data within one iterative process. The BID algorithm applied, loops the iteration until the minimum level of chi-square parameter is obtained (between data and convolution of restoredPSF and restored image). In SXT flare images, especially of compact sources ones, signal values are often non-uniformly distributed in their range. Therefore, objects to compare for chi-square minimization are previously Fourier transformed what makes the distribution of their signal values more even and chi-square comparison more meaningful. As the performance and speed of the blind deconvolution algorithms strongly depend on data selection and good initial approximation of the PSF function, extensive preparations have been completed to collect appropriate observational material for BID deconvolution ends. The period of data selection has been constrained to the year 2000. A period relatively short in comparison with Yohkoh mission duration but long enough to ensure good data coverage. First, all images from the year 2000 present in the database of SXT compact sources seen in thick aluminum filter images (Gburek, Sylwester, 2001) were processed and reduced. Then the Fourier transforms of the data have been additionally checked for their value distribution. Eventually, above 2500 images has been selected for BID restorations. ReferencesAyers G. R., Dainty J. C., Iterative blind deconvolution method and its applications, Optic Letters, vol .13, no. 7, 1988Martens P., Acton L., Lemen J., The Point Spread Function of the Soft X-ray Telescope Aboard Yohkoh, Sol. Phys. 157, 141, 1995. Gburek S., Sylwester J. Search for Compact X-ray Sources, in SXT Observations, submitted to Sol. Phys. 2001 URL referencesDECON 2001 meeting summary |