ULTRA l2 add backwards compatibility for old PSETS (#2928)

* add backwards compatibility for old psets

* fix check

* temporary test for coverage

Author: lacoak21

imap_processing/ena_maps/ena_maps.py

@@ -627,6 +627,14 @@ def downsample_counts(self) -> None:
         nside of the input pset counts variable (e.g. 128) to the nside of the pset.
         """
         pset_data = self.data
+        # TODO remove this check once we reprocess all psets
+        #  going forward, all psets should have counts_pixel_index as a coordinate.
+        if "counts_pixel_index" not in pset_data.dims:
+            logger.info(
+                "No counts_pixel_index found in the dataset. Skipping counts "
+                "downsampling."
+            )
+            return
         counts_n_pix = pset_data.sizes["counts_pixel_index"]
         pset_n_pix = hp.nside2npix(self.nside)
         if counts_n_pix != pset_n_pix:

imap_processing/tests/ena_maps/test_ena_maps.py

@@ -98,6 +98,16 @@ def test_instantiate(self):
                 "energy_bin_geometric_mean",
             )
 
+    # TODO remove this test when the TODO in the ultra downsample_counts function is
+    # removed.
+    def test_old_pset(self):
+        pset = self.l1c_pset_products[0]
+        pset = pset.drop_dims("counts_pixel_index")
+        pset = ena_maps.UltraPointingSet(
+            pset,
+            spice_reference_frame=geometry.SpiceFrame.IMAP_DPS,
+        )
+
     @pytest.mark.usefixtures("_setup_ultra_l1c_pset_products")
     def test_init_cdf(
         self,