Populate sky metadata with zero if matching is not possible. (spacete…

…lescope#1360)

CHANGES.rst

@@ -77,6 +77,11 @@ tweakreg
 
 - Update default absolute separation for tweakreg. [#1352]
 
+skymatch
+--------
+- Populate valid metadata even when then are no overlapping images to
+ match [#1360]
+
 
 0.15.1 (2024-05-15)
 ===================

romancal/skymatch/skymatch_step.py

@@ -174,13 +174,14 @@ def _imodel2skyim(self, image_model):
  def _set_sky_background(self, sky_image, step_status):
  image = sky_image.meta["image_model"]
  sky = sky_image.sky
+ if sky == 0 or sky is None:
+ sky = 0 * image.data.unit
 
- if step_status == "COMPLETE":
- image.meta.background.method = str(self.skymethod)
- image.meta.background.level = sky
- image.meta.background.subtracted = self.subtract
+ image.meta.background.method = str(self.skymethod)
+ image.meta.background.subtracted = self.subtract
+ image.meta.background.level = sky
 
-  if self.subtract:
-  image.data[...] = sky_image.image[...]
+ if step_status == "COMPLETE" and self.subtract:
+ image.data[...] = sky_image.image[...]
 
  image.meta.cal_step.skymatch = step_status