Add slstr

pyorbital/geoloc_instrument_definitions.py

@@ -548,3 +548,29 @@ def ascat(scan_nb, scan_points=None):
                      [np.int32(scan_nb), 1]) + np.expand_dims(offset, 1))
 
     return ScanGeometry(inst, times)
+
+
+def slstr_nadir(scans_nb, scan_points=None):
+    """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 scan_points is None:
+        scan_len = 3000  # samples per scan
+        scan_points = np.arange(scan_len)
+    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

@@ -22,12 +22,13 @@
 
 """Test the geoloc module."""
 
+
 from datetime import datetime
 
 import numpy as np
 
 from pyorbital.geoloc import ScanGeometry, geodetic_lat, qrotate, subpoint
-from pyorbital.geoloc_instrument_definitions import amsua, ascat, atms, avhrr, hirs4, mhs, viirs
+from pyorbital.geoloc_instrument_definitions import amsua, ascat, atms, avhrr, hirs4, mhs, slstr_nadir, viirs
 
 
 class TestQuaternion:
@@ -291,3 +292,16 @@ def test_ascat(self):
         geom = ascat(1, np.array([0, -1]))
         np.testing.assert_allclose(
             geom.fovs, expected_fovs, rtol=1e-2, atol=1e-2)
+
+    def test_slstr_nadir(self):
+        """Test the definition of the slstr instrument nadir view flying on Sentinel-3."""
+        geom = slstr_nadir(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)
+        np.testing.assert_allclose(geom.fovs, expected_fovs, rtol=1e-2, atol=1e-2)
+
+        geom = slstr_nadir(1, None)
+
+        np.testing.assert_equal(geom.fovs.size, 6000)