Changes between Version 6 and Version 7 of IPP_Progress_Report_20091207

Timestamp:

Dec 15, 2009, 5:38:12 PM (17 years ago)

Author:

eugene

Comment:

--

IPP_Progress_Report_20091207

@@ -5 +5 @@
 
 === Eugene Magnier ===
+
+I have continued to work on the behavior of psphot in the context of ppSub.  I spent part of the week examining the degeneracy of the convolution kernels, and attempting to address the degeneracy with SVD.  The plan was to eliminating the modes which did not significantly reduce the chi-square, but this was not very successful: eliminating even the lowest order modes seems to increase the noise in the bright star residuals.  My conclusion is that the only avenue for progress in this area is to choose convolution kernels which are more explicitly orthgonal.  Since the actual basis function is the kernel convolved with the PSF, this may require an iterative analysis of a range of kernels.  
+
+I then worked on the behavior of psphot when operating on the difference images.  I fixed a few issues in the visualization that made it difficult to see where psphot was having trouble.  That allowed me to identify a specific issue: the source moments analysis, used to guess the psf shape in the positive image analysis, was being re-run on the difference image.  Since at this stage, there are few real detections, and most detections are faint, the results of that analysis are suspect.  In fact, a typical result is that the sources are mis-classified as possible cosmic rays or defects.  The bug that caused this behavior was a failure to pass all of the psf model information to this psphot analysis.  By addressing this bug, I was able to demonstrate good photometry analysis of the transient difference sources is simulated images, including consistency with the input magnitudes of those transient sources.
 
 === Heather Flewelling ===