Merge pull request #105 from astrojuanlu/fix-los-corner-case

Fix LOS computation corner case

CHANGELOG.txt

@@ -1,5 +1,9 @@
 # orbit-predictor changelog
 
+## 1.13.2 (2020-09-28)
+
+* Make LOS computation more robust in new pass predictor
+
 ## 1.13.1 (2020-09-28)
 
 * Fix version number

orbit_predictor/predictors/pass_iterators.py

@@ -264,11 +264,11 @@ def elevation(delta_seconds):
         # Ensure location is visible at AOS by adding atol
         aos = start_date + dt.timedelta(seconds=t_aos + self.tolerance_s)
 
-        # LOS must be between TCA and an elapsed time around (TCA - AOS)
+        # LOS must be between TCA and half the next period
         try:
             t_los = root_scalar(
                 lambda t: elevation(t) - self.aos_at,
-                bracket=(t_tca, t_tca + (t_tca - t_aos) + 60),
+                bracket=(t_tca, t_tca + period_s / 2),
                 xtol=self.tolerance_s,
             ).root
         except ValueError as e:

orbit_predictor/version.py

@@ -1,2 +1,2 @@
 # https://www.python.org/dev/peps/pep-0440/
-__version__ = '1.13.1'
+__version__ = '1.13.2'

tests/test_accurate_predictor.py

@@ -294,3 +294,39 @@ def test_pass_is_not_skipped_smart(self):
         ))
 
         assert predicted_passes
+
+
+class LOSComputationRegressionTests(TestCase):
+    """Check that we the LOS is computed correctly"""
+    # See https://github.com/satellogic/orbit-predictor/issues/104
+
+    def setUp(self):
+        tle_lines = (
+            "1 42760U 17034C   19070.46618549  .00000282  00000-0  30543-4 0  9995",
+            "2 42760  43.0166  56.1509 0009676 356.3576 146.0151 15.09909885 95848",
+        )
+        self.db = MemoryTLESource()
+        self.db.add_tle("42760U", tle_lines, dt.datetime.now())
+        self.predictor = TLEPredictor("42760U", self.db)
+
+    @pytest.mark.skipif(sys.version_info < (3, 5), reason="Not installing SciPy in Python 3.4")
+    def test_los_is_correctly_computed(self):
+        loc = Location(
+            name='loc',
+            latitude_deg=-34.61315,
+            longitude_deg=-58.37723,
+            elevation_m=30,
+        )
+
+        PASS_DATE = dt.datetime(2019, 1, 1, 0, 0)
+        LIMIT_DATE = dt.datetime(2019, 1, 15, 0, 0)
+
+        predicted_passes = list(self.predictor.passes_over(
+            loc,
+            when_utc=PASS_DATE,
+            limit_date=LIMIT_DATE,
+            aos_at_dg=0, max_elevation_gt=0,
+            location_predictor_class=SmartLocationPredictor,
+        ))
+
+        assert predicted_passes