Support case-insensitive query criteria

CHANGES.rst

@@ -188,6 +188,9 @@ mast
 - Present users with an error rather than a warning when nonexistent query criteria are used in ``mast.Observations.query_criteria``
   and ``mast.Catalogs.query_criteria``. [#3084]
 
+- Support for case-insensitive criteria keyword arguments in ``mast.Observations.query_criteria`` and 
+  ``mast.Catalogs.query_criteria``. [#3087]
+
 
 0.4.7 (2024-03-08)
 ==================

astroquery/mast/discovery_portal.py

@@ -404,8 +404,8 @@ def build_filter_set(self, column_config_name, service_name=None, **filters):
             if np.isscalar(value,):
                 value = [value]
 
-            # Get the column type and separator
-            col_info = caom_col_config.get(colname)
+            # Get the column type and separator with case-insensitive lookup
+            col_info = next((v for k, v in caom_col_config.items() if k.lower() == colname.lower()), None)
             if not col_info:
                 closest_match = difflib.get_close_matches(colname, caom_col_config.keys(), n=1)
                 error_msg = f"Filter '{colname}' does not exist. Did you mean '{closest_match[0]}'?" if closest_match \

astroquery/mast/tests/test_mast_remote.py

@@ -274,6 +274,13 @@ def test_observations_query_criteria(self):
                                              intentType="calibration")
         assert (result["intentType"] == "calibration").all()
 
+        # with case-insensitive keyword arguments
+        result = Observations.query_criteria(Instrument_Name="*WFPC2*",
+                                             proposal_ID=8169,
+                                             T_min=[51361, 51362])
+        assert isinstance(result, Table)
+        assert len(result) == 13
+
     def test_observations_query_criteria_invalid_keyword(self):
         # attempt to make a criteria query with invalid keyword
         with pytest.raises(InvalidQueryError) as err_no_alt:
@@ -892,6 +899,18 @@ def check_result(result, exp_vals):
         assert isinstance(result, Table)
         assert result['distance'][0] <= result['distance'][1]
 
+        # with case-insensitive keyword arguments
+        result = Catalogs.query_criteria(catalog="Tic",
+                                         bMAG=[30, 50],
+                                         objtype="STAR")
+        check_result(result, {'ID': '81609218'})
+
+        result = Catalogs.query_criteria(catalog="DiskDetective",
+                                         STATE=["inactive", "disabled"],
+                                         oVaL=[8, 10],
+                                         Multi=[3, 7])
+        check_result(result, {'designation': 'J003920.04-300132.4'})
+
     def test_catalogs_query_criteria_invalid_keyword(self):
         # attempt to make a criteria query with invalid keyword
         with pytest.raises(InvalidQueryError) as err_no_alt: