fix(seviri): include the first IR row when converting RSR data

pyspectral/tests/test_seviri_rsr.py

@@ -0,0 +1,48 @@
+"""Regression tests for the SEVIRI RSR converter.
+
+Ensures the first spreadsheet row of each IR channel is included when
+converting the bundled MSG SEVIRI spectral response workbook (issue #253).
+"""
+
+import importlib
+import sys
+import types
+from pathlib import Path
+
+from xlrd import open_workbook
+
+
+def _import_seviri_module(repo_root: Path):
+    sys.modules.pop("rsr_convert_scripts.seviri_rsr", None)
+    sys.modules["pkg_resources"] = types.SimpleNamespace(
+        resource_filename=lambda package, resource: str(repo_root / "pyspectral" / "data")
+    )
+    return importlib.import_module("rsr_convert_scripts.seviri_rsr")
+
+
+def test_ir_channels_include_the_first_spreadsheet_row(monkeypatch):
+    """IR channel RSR data must start at spreadsheet row 12, not row 13."""
+    repo_root = Path(__file__).resolve().parents[2]
+    xls_path = repo_root / "pyspectral" / "data" / "MSG_SEVIRI_Spectral_Response_Characterisation.XLS"
+    workbook = open_workbook(str(xls_path))
+    sheet = workbook.sheet_by_name("IR7.3")
+
+    # The issue's concrete repro: the first wavelength/data row is line 13 in the
+    # spreadsheet UI, which is row index 12 for xlrd.
+    assert sheet.cell_value(12, 0) == 6.35
+    assert sheet.cell_value(13, 0) == 6.37
+
+    seviri_rsr = _import_seviri_module(repo_root)
+    monkeypatch.setattr(
+        seviri_rsr,
+        "get_config",
+        lambda: {
+            "seviri": {"path": str(xls_path), "filename": xls_path.name},
+            "rsr_dir": str(repo_root / "tmp-rsr"),
+        },
+    )
+
+    seviri = seviri_rsr.Seviri()
+
+    assert seviri.rsr["IR7.3"]["wavelength"][0] == sheet.cell_value(12, 0)
+    assert seviri.rsr["IR7.3"]["Meteosat-11"]["95"][0] == sheet.cell_value(12, 7)

rsr_convert_scripts/seviri_rsr.py

@@ -91,23 +91,23 @@ def _load(self, filename=None):
                 self.rsr[ch_name]['Meteosat-11'] = met11
             elif ch_name.startswith('IR'):
                 wvl = np.array(
-                    sheet.col_values(0, start_rowx=13, end_rowx=113))
+                    sheet.col_values(0, start_rowx=12, end_rowx=112))
                 met8_95 = np.array(
-                    sheet.col_values(1, start_rowx=13, end_rowx=113))
+                    sheet.col_values(1, start_rowx=12, end_rowx=112))
                 met9_95 = np.array(
-                    sheet.col_values(3, start_rowx=13, end_rowx=113))
+                    sheet.col_values(3, start_rowx=12, end_rowx=112))
                 met10_95 = np.array(
-                    sheet.col_values(5, start_rowx=13, end_rowx=113))
+                    sheet.col_values(5, start_rowx=12, end_rowx=112))
                 met11_95 = np.array(
-                    sheet.col_values(7, start_rowx=13, end_rowx=113))
+                    sheet.col_values(7, start_rowx=12, end_rowx=112))
                 met8_85 = np.array(
-                    sheet.col_values(2, start_rowx=13, end_rowx=113))
+                    sheet.col_values(2, start_rowx=12, end_rowx=112))
                 met9_85 = np.array(
-                    sheet.col_values(4, start_rowx=13, end_rowx=113))
+                    sheet.col_values(4, start_rowx=12, end_rowx=112))
                 met10_85 = np.array(
-                    sheet.col_values(6, start_rowx=13, end_rowx=113))
+                    sheet.col_values(6, start_rowx=12, end_rowx=112))
                 met11_85 = np.array(
-                    sheet.col_values(8, start_rowx=13, end_rowx=113))
+                    sheet.col_values(8, start_rowx=12, end_rowx=112))
                 self.rsr[ch_name]['Meteosat-8'] = {'95': met8_95,
                                                    '85': met8_85}
                 self.rsr[ch_name]['Meteosat-9'] = {'95': met9_95,