From 280ebd6406663f1eb2e8e49527f07a1474ece5bb Mon Sep 17 00:00:00 2001
From: Simon Proud <simon.proud@esa.int>
Date: Thu, 29 Aug 2024 11:46:25 +0200
Subject: [PATCH] Update VIIRS L1b reader to use additional netcdf attributes

---
 satpy/readers/viirs_l1b.py                 | 18 ++++++++++++++++++
 satpy/tests/reader_tests/test_viirs_l1b.py |  6 ++++++
 2 files changed, 24 insertions(+)

diff --git a/satpy/readers/viirs_l1b.py b/satpy/readers/viirs_l1b.py
index 7dd3079dbb..c0433b38a3 100644
--- a/satpy/readers/viirs_l1b.py
+++ b/satpy/readers/viirs_l1b.py
@@ -34,6 +34,21 @@ def _parse_datetime(self, datestr):
         """Parse datetime."""
         return dt.datetime.strptime(datestr, "%Y-%m-%dT%H:%M:%S.000Z")
 
+    @property
+    def day_night_flag(self):
+        """Get the day/night flag."""
+        return self["/attr/DayNightFlag"]
+
+    @property
+    def start_direction(self):
+        """Get the swath start direction flag."""
+        return self["/attr/startDirection"]
+
+    @property
+    def end_direction(self):
+        """Get the swath end direction flag."""
+        return self["/attr/endDirection"]
+
     @property
     def start_orbit_number(self):
         """Get start orbit number."""
@@ -188,6 +203,9 @@ def get_metadata(self, dataset_id, ds_info):
             "file_units": file_units,
             "platform_name": self.platform_name,
             "sensor": self.sensor_name,
+            "day_night": self.day_night_flag,
+            "start_direction": self.start_direction,
+            "end_direction": self.end_direction,
             "start_orbit": self.start_orbit_number,
             "end_orbit": self.end_orbit_number,
         })
diff --git a/satpy/tests/reader_tests/test_viirs_l1b.py b/satpy/tests/reader_tests/test_viirs_l1b.py
index b2a5c4b476..c8a5468fc7 100644
--- a/satpy/tests/reader_tests/test_viirs_l1b.py
+++ b/satpy/tests/reader_tests/test_viirs_l1b.py
@@ -65,6 +65,9 @@ def get_test_content(self, filename, filename_info, filetype_info):
             "/attr/orbit_number": 26384,
             "/attr/instrument": "VIIRS",
             "/attr/platform": "Suomi-NPP",
+            "/attr/DayNightFlag": "Day",
+            "/attr/startDirection": "Descending",
+            "/attr/endDirection": "Ascending",
         }
         self._fill_contents_with_default_data(file_content, file_type)
         self._set_dataset_specific_metadata(file_content)
@@ -271,6 +274,9 @@ def test_load_every_m_band_rad(self):
             assert v.attrs["area"].lons.attrs["rows_per_scan"] == 2
             assert v.attrs["area"].lats.attrs["rows_per_scan"] == 2
             assert v.attrs["sensor"] == "viirs"
+            assert v.attrs["day_night"] == "Day"
+            assert v.attrs["start_direction"] == "Descending"
+            assert v.attrs["end_direction"] == "Ascending"
 
     def test_load_i_band_angles(self):
         """Test loading all M bands as radiances."""