Add slstr

pyorbital/geoloc_instrument_definitions.py

@@ -553,3 +553,33 @@ def ascat(scan_nb, scan_points=None):
                      [np.int32(scan_nb), 1]) + np.expand_dims(offset, 1))
 
     return ScanGeometry(inst, times)
+
+
+def slstr(scans_nb, scan_points=None, is_nadir=True):
+    """Definition of the SLSTR instrument Nadir swath.
+
+    Source: Sentinel-3 SLSTR Coverage
+    https://sentinel.esa.int/web/sentinel/user-guides/Sentinel-3-slstr/coverage
+    """
+
+    if not is_nadir:
+        raise NotImplementedError("SLSTR is only implemented for Nadir view.")
+
+    if scan_points is None:
+        scan_len = 3000  # samples per scan
+        scan_points = np.arange(3000)
+    else:
+        scan_len = len(scan_points)
+    scan_angle_west = 46.5  # swath, degrees
+    scan_angle_east = -22.1  # swath, degrees
+
+    # build the slstr instrument scan line angles
+    scanline_angles = np.linspace(np.deg2rad(scan_angle_west),
+                                  np.deg2rad(scan_angle_east), scan_len)
+    inst = np.vstack((scanline_angles, np.zeros(scan_len,)))
+
+    inst = np.tile(inst[:, np.newaxis, :], [1, np.int32(scans_nb), 1])
+
+    times = np.tile(np.zeros_like(scanline_angles), [np.int32(scans_nb), 1])
+
+    return ScanGeometry(inst, times)

pyorbital/tests/test_geoloc.py

@@ -28,7 +28,7 @@
 import numpy as np
 
 from pyorbital.geoloc import ScanGeometry, geodetic_lat, qrotate, subpoint
-from pyorbital.geoloc_instrument_definitions import avhrr, viirs, amsua, mhs, hirs4, atms, ascat
+from pyorbital.geoloc_instrument_definitions import avhrr, viirs, amsua, mhs, hirs4, atms, ascat, slstr
 
 
 class TestQuaternion(unittest.TestCase):
@@ -287,6 +287,19 @@ def test_ascat(self):
         self.assertTrue(np.allclose(
             geom.fovs, expected_fovs, rtol=1e-2, atol=1e-2))
 
+    def test_slstr(self):
+        """Test the definition of the slstr instrument flying on Sentinel-3
+        """
+        geom = slstr(1, [0, 1])
+
+        expected_fovs = np.array([
+            np.tile(np.array([[0.8115781, -0.38571776]]), [1, 1]),
+            np.tile(np.array([[0., 0.]]), [1, 1])], dtype=np.float64)
+        self.assertTrue(np.allclose(geom.fovs,
+                                    expected_fovs, rtol=1e-2, atol=1e-2))
+
+        with self.assertRaises(NotImplementedError):
+            slstr(1, [0, 1], is_nadir=False)
 
 def suite():
     """The suite for test_geoloc