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The use of rotation modulation collimators for hard X-ray imaging has been proposed for the High Energy Solar Physics (HESP) mission and for the balloon-borne High Energy Imaging Device (HEIDI). For this sort of telescope, considerable processing of the data is required in order to get useful images. In order to test the processing methods, we have made simulated images of solar hard X-ray bursts based on prototype Yohkoh SXT flares. For our purposes, we believe that it is more straightforward to use the initial kernels of the soft X-ray flares, instead of HXT images of hard X-ray sources, since the HXT images are already highly processed themselves. Our basic assumption is that the hard X-rays come from the same points where the initial soft X-rays are emitted.
These artificial hard X-ray images, when passed through the HESP simulator, produce ``dirty'' maps, which have to be deconvolved to produce ``clean'' maps. We have applied several different deconvolution techniques, among them a specialized CLEAN algorithm (based on the radio astronomy procedure), the Richardson-Lucy algorithm (well-known for its use on HST images), and the Maximum Entropy Method.
We will discuss the advantages and disadvantages of each technique, with examples of different flares, levels of noise, and photon-counting statistics.
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