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Дата изменения: Mon Apr 18 17:45:42 1994
Дата индексирования: Sun Dec 23 19:49:19 2007
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Поисковые слова: arp 220
Problem Statement



Next: Solution Up: Simultaneous Phase Retrieval and Previous: Data Model

Problem Statement

Following Snyder, Hammoud, and White (1993), we simplify the noise model by defining the modified data

and by considering the situation in which the CCD read-out noise variance is large. In this case, the modified data are approximately equal in distribution to a Poisson process whose mean function is

Therefore, the pseudo-log-likelihood takes the form

where terms that do not depend on the unknown object or parameters have been omitted. The maximum likelihood estimator of these parameters will maximize for a particular data set , subject to the physical constraint that the object estimate be a nonnegative function. An explicit, closed form solution to this problem is not known. Therefore, in the next section we propose a technique for producing estimates numerically by using the expectation-maximization (EM) algorithm (Dempster et al. 1977).


rlw@sundog.stsci.edu
Mon Apr 18 09:34:19 EDT 1994