Use explicit channel names

satpy/readers/utils.py

@@ -477,53 +477,79 @@ def remove_earthsun_distance_correction(reflectance, utc_date=None):
 
 
 class CalibrationCoefficientSelector:
-    """Helper for choosing coefficients out of multiple options."""
+    """Helper for choosing coefficients out of multiple options.
+
+    Example: Three sets of coefficients are available (nominal, meirink, gsics).
+    Calibrate channel 1 with "meirink" and channels 2/3 with "gsics".
+
+    1. Setup
+
+    .. code-block:: python
+
+        from satpy.readers.utils import CalibrationCoefficientSelector
+        from satpy.tests.utils import make_dataid
+
+        coefs = {
+            "nominal": {
+                "ch1": "nominal_ch1",
+                "ch2": "nominal_ch2",
+                "ch3": "nominal_ch3"
+            },
+            "meirink": {
+                "ch1": "meirink_ch1",
+            },
+            "gsics": {
+                "ch2": "gsics_ch2",
+                # ch3 coefficients are missing
+            }
+        }
+        modes = {
+            "meirink": ["ch1"],
+            "gsics": ["ch2", "ch3"]
+        }
+
+        ch1 = make_dataid(name="ch1")
+        ch2 = make_dataid(name="ch2")
+        ch3 = make_dataid(name="ch3")
+
+    2. Query:
+
+    .. code-block:: python
+
+        >>> s = CalibrationCoefficientSelector(coefs, modes)
+        >>> s.get_coefs(ch1)
+        "meirink_ch1"
+        >>> s.get_coefs(ch2)
+        "gsics_ch2"
+        >>> s.get_coefs(ch3)
+        KeyError: 'No gsics calibration coefficients for ch3'
+
+    3. Fallback to nominal for ch3:
+
+    .. code-block:: python
+
+        >>> s = CalibrationCoefficientSelector(coefs, modes, fallback="nominal")
+        >>> s.get_coefs(ch3)
+        "nominal_ch3"
+    """
 
-    def __init__(self, coefs, modes=None, default="nominal", fallback=None, refl_threshold=1):
+    def __init__(self, coefs, modes=None, default="nominal", fallback=None):
         """Initialize the coefficient selector.
 
         Args:
-            coefs (dict): One set of calibration coefficients for each calibration
-                mode, for example ::
-
-                    {
-                        "nominal": {
-                            "ch1": nominal_coefs_ch1,
-                            "ch2": nominal_coefs_ch2
-                        },
-                        "gsics": {
-                            "ch2": gsics_coefs_ch2
-                        }
-                    }
-
-                The actual coefficients can be of any type (reader-specific).
-
-            modes (dict): Desired calibration modes per channel type ::
-
-                    {
-                        "reflective": "nominal",
-                        "emissive": "gsics"
-                    }
-
-                or per channel ::
-
-                    {
-                        "VIS006": "nominal",
-                        "IR_108": "gsics"
-                    }
-
+            coefs (dict): One set of calibration coefficients for each
+                calibration mode. The actual coefficients can be of any type
+                (reader-specific).
+            modes (dict): Desired calibration modes
             default (str): Default coefficients to be used if no mode has been
                 specified. Default: "nominal".
             fallback (str): Fallback coefficients if the desired coefficients
                 are not available for some channel.
-            refl_threshold: Central wavelengths below/above this threshold are
-                considered reflective/emissive. Default is 1um.
         """
         self.coefs = coefs
         self.modes = modes or {}
         self.default = default
         self.fallback = fallback
-        self.refl_threshold = refl_threshold
         if self.default not in self.coefs:
             raise KeyError("Need at least default coefficients")
         if self.fallback and self.fallback not in self.coefs:
@@ -548,19 +574,7 @@ def _get_coefs(self, dataset_id, mode):
             raise KeyError(f"No {mode} calibration coefficients for {ds_name}")
 
     def _get_mode(self, dataset_id):
-        try:
-            return self._get_mode_for_channel(dataset_id)
-        except KeyError:
-            return self._get_mode_for_channel_type(dataset_id)
-
-    def _get_mode_for_channel(self, dataset_id):
-        return self.modes[dataset_id["name"]]
-
-    def _get_mode_for_channel_type(self, dataset_id):
-        ch_type = self._get_channel_type(dataset_id)
-        return self.modes.get(ch_type, self.default)
-
-    def _get_channel_type(self, dataset_id):
-        if dataset_id["wavelength"].central < self.refl_threshold:
-            return "reflective"
-        return "emissive"
+        for mode, channels in self.modes.items():
+            if dataset_id["name"] in channels:
+                return mode
+        return self.default

satpy/tests/reader_tests/test_utils.py

@@ -538,16 +538,12 @@ def fixture_coefs(self):
     @pytest.fixture(name="ch1")
     def fixture_ch1(self):
         """Make fake data ID."""
-        return make_dataid(name="ch1", wavelength=(0.6, 0.7, 0.8))
-
-    @pytest.fixture(name="ch2")
-    def fixture_ch2(self):
-        """Make fake data ID."""
-        return make_dataid(name="ch2", wavelength=(10, 11, 12))
+        return make_dataid(name="ch1")
 
     @pytest.fixture(name="dataset_ids")
-    def fixture_dataset_ids(self, ch1, ch2):
+    def fixture_dataset_ids(self, ch1):
         """Make fake data IDs."""
+        ch2 = make_dataid(name="ch2")
         return [ch1, ch2]
 
     @pytest.mark.parametrize(
@@ -558,16 +554,16 @@ def fixture_dataset_ids(self, ch1, ch2):
                 {"ch1": "nominal_ch1", "ch2": "nominal_ch2"}
             ),
             (
-                {"reflective": "mode1"},
-                {"ch1": "mode1_ch1", "ch2": "nominal_ch2"}
+                {"nominal": ["ch1", "ch2"]},
+                {"ch1": "nominal_ch1", "ch2": "nominal_ch2"}
             ),
             (
-                {"reflective": "mode1", "emissive": "mode2"},
-                {"ch1": "mode1_ch1", "ch2": "mode2_ch2"}
+                {"mode1": ["ch1"]},
+                {"ch1": "mode1_ch1", "ch2": "nominal_ch2"}
             ),
             (
-                {"ch1": "mode1"},
-                {"ch1": "mode1_ch1", "ch2": "nominal_ch2"}
+                {"mode1": ["ch1"], "mode2": ["ch2"]},
+                {"ch1": "mode1_ch1", "ch2": "mode2_ch2"}
             ),
         ]
     )
@@ -582,14 +578,14 @@ def test_get_coefs(self, dataset_ids, coefs, calib_modes, expected):
 
     def test_missing_coefs(self, coefs, ch1):
         """Test handling of missing coefficients."""
-        calib_modes = {"reflective": "mode2"}
+        calib_modes = {"mode2": ["ch1"]}
         s = CalibrationCoefficientSelector(coefs, calib_modes)
         with pytest.raises(KeyError, match="No mode2 calibration *"):
             s.get_coefs(ch1)
 
     def test_fallback_to_nominal(self, coefs, ch1):
         """Test falling back to nominal coefficients."""
-        calib_modes = {"reflective": "mode2"}
+        calib_modes = {"mode2": ["ch1"]}
         s = CalibrationCoefficientSelector(coefs, calib_modes, fallback="nominal")
         assert s.get_coefs(ch1) == "nominal_ch1"