ENH: Resolve pressure_ISA discretization bounds TODO

CHANGELOG.md

@@ -60,6 +60,7 @@ Attention: The newest changes should be on top -->
 
 ### Changed
 
+- ENH: Resolve pressure_ISA discretization bounds TODO [#1056](https://github.com/RocketPy-Team/RocketPy/pull/1056)
 - ENH: Refactor flight.py latitude/longitude to use inverted_haversine [#1055](https://github.com/RocketPy-Team/RocketPy/pull/1055)
 
 ### Deprecated

rocketpy/environment/environment.py

@@ -2553,7 +2553,9 @@ def pressure_function(h):
             return P
 
         # Discretize this Function to speed up the trajectory simulation
-        altitudes = np.linspace(0, 80000, 100)  # TODO: should be -2k instead of 0
+        min_height = geopotential_height_to_geometric_height(-2000, earth_radius)
+        max_height = geopotential_height_to_geometric_height(80000, earth_radius)
+        altitudes = np.linspace(min_height, max_height, 100)
         pressures = [pressure_function(h) for h in altitudes]
 
         return np.column_stack([altitudes, pressures])

tests/unit/environment/test_environment.py

@@ -707,3 +707,27 @@ def test_pressure_conversion_factor_autodetect_by_model(
         None, None, model
     )
     assert factor == expected_factor
+
+
+def test_pressure_isa_discretization_bounds(example_plain_env):
+    """Test that pressure_ISA contains the expected range of altitudes
+    starting from the minimum geopotential height (-2000m) converted to
+    geometric height, up to the maximum (80000m) geopotential height converted to
+    geometric height.
+    """
+    from rocketpy.tools import geopotential_height_to_geometric_height
+
+    # Act
+    pressure_isa_function = example_plain_env.pressure_ISA
+    source_array = pressure_isa_function.source
+    altitudes = source_array[:, 0]
+
+    # Expected min/max geometric heights
+    earth_radius = example_plain_env.earth_radius
+    expected_min_height = geopotential_height_to_geometric_height(-2000, earth_radius)
+    expected_max_height = geopotential_height_to_geometric_height(80000, earth_radius)
+
+    # Assert
+    assert np.isclose(altitudes[0], expected_min_height)
+    assert np.isclose(altitudes[-1], expected_max_height)
+    assert len(altitudes) == 100