JP-3148: Trap source catalog errors in tweakreg (spacetelescope#7507)

* JP-3148: Trap source catalog errors in tweakreg

* add change log entry

* Incorporate Mihai's suggestions

* update change log

CHANGES.rst

@@ -107,7 +107,6 @@ ramp_fitting
 - Update ramp fitting to calculate separate readnoise variance for processing
   ``undersampling_correction`` output [#7484]
 
-
 resample
 --------
 
@@ -138,15 +137,16 @@ straylight
 
 - Fix bug with straylight zeroing out NaNs in input rate images, as these
   are now deliberately set as such [#7455]
-- Move ``jwst.datamodels`` out of ``jwst`` into ``stdatamodels.jwst.datamodels``. [#7439]
 
 scripts
 -------
 
 - Added a script ``adjust_wcs.py`` to apply additional user-provided rotations
   and scale corrections to an imaging WCS of a calibrated image. [#7430]
+
 - Update ``minimum_deps`` script to use ``importlib_metadata`` and ``packaging``
   instead of ``pkg_resources``. [#7457]
+
 - Offload ``minimum_deps`` script to ``minimum_dependencies`` package [#7463]
 
 transforms
@@ -167,6 +167,9 @@ tweakreg
 - Fixed a bug due to which alignment may be aborted due to corrections
   being "too large" yet compatible with step parameters. [#7494]
 
+- Added a trap for failures in source catalog construction, which now returns
+  an empty catalog for the image on which the error occurred. [#7507]
+
 undersampling_correction
 ------------------------
 

jwst/tweakreg/tweakreg_catalog.py

@@ -1,3 +1,5 @@
+import logging
+
 from astropy.table import Table
 import numpy as np
 from photutils.detection import DAOStarFinder
@@ -6,6 +8,9 @@
 
 from ..source_catalog.detection import JWSTBackground
 
+log = logging.getLogger(__name__)
+log.setLevel(logging.DEBUG)
+
 
 def make_tweakreg_catalog(model, kernel_fwhm, snr_threshold, sharplo=0.2,
                           sharphi=1.0, roundlo=-1.0, roundhi=1.0,
@@ -73,10 +78,17 @@ def make_tweakreg_catalog(model, kernel_fwhm, snr_threshold, sharplo=0.2,
                       dqflags.pixel['DO_NOT_USE']) &
                      model.dq).astype(bool)
 
-    bkg = JWSTBackground(model.data, box_size=bkg_boxsize,
-                         coverage_mask=coverage_mask)
+    columns = ['id', 'xcentroid', 'ycentroid', 'flux']
+    try:
+        bkg = JWSTBackground(model.data, box_size=bkg_boxsize,
+                             coverage_mask=coverage_mask)
+        threshold_img = bkg.background + (snr_threshold * bkg.background_rms)
+    except ValueError as e:
+        log.warning(f"Error determining sky background: {e.args[0]}")
+        # return an empty catalog
+        catalog = Table(names=columns, dtype=(int, float, float, float))
+        return catalog
 
-    threshold_img = bkg.background + (snr_threshold * bkg.background_rms)
     threshold = np.median(threshold_img)  # DAOStarFinder requires float
 
     daofind = DAOStarFinder(fwhm=kernel_fwhm, threshold=threshold,
@@ -85,7 +97,6 @@ def make_tweakreg_catalog(model, kernel_fwhm, snr_threshold, sharplo=0.2,
                             peakmax=peakmax)
     sources = daofind(model.data, mask=coverage_mask)
 
-    columns = ['id', 'xcentroid', 'ycentroid', 'flux']
     if sources:
         catalog = sources[columns]
     else: