Merge pull request #1000 from lsst/tickets/DM-46852

DM-46852: Return None for the PSF if the computed shape is NAN

python/lsst/pipe/tasks/finalizeCharacterization.py

@@ -716,6 +716,13 @@ def compute_psf_and_ap_corr_map(self, visit, detector, exposure, src, isolated_s
             self.log.warning('Failed to determine psf for visit %d, detector %d: %s',
                              visit, detector, e)
             return None, None, measured_src
+        # Verify that the PSF is usable by downstream tasks
+        sigma = psf.computeShape(psf.getAveragePosition()).getDeterminantRadius()
+        if np.isnan(sigma):
+            self.log.warning('Failed to determine psf for visit %d, detector %d: '
+                             'Computed final PSF size is NAN.',
+                             visit, detector)
+            return None, None, measured_src
 
         # Set the psf in the exposure for measurement/aperture corrections.
         exposure.setPsf(psf)