Scenarios – ephemerista.scenarios

The scenarios.py module.

This module provides the Scenario class which collects all required inputs such as assets, communications channels, points and areas of interest for orbit propagation and analyses.

pydantic model ephemerista.scenarios.Ensemble

The Ensemble model.

This class collects the resulting trajectories from propagating the state of all assets within a scenario.

Fields:
field ephemerides: dict[str, Trajectory] = {}
field trajectories: dict[Annotated[UUID], Trajectory] [Required]

Dictionary of trajectories indexed by asset IDs

add_earth_attitude()

Add attitude quaternions for Earth to the ensemble.

class ephemerista.scenarios.Rectangle(coords)

A rectangle type that has a simple Geo JSON interface.

Created so we don’t use the costly to create Shapely. Polygon objects that are not needed. We only need the __geo_interface__ implementation. Note that we are checking nothing here, as we expect a well-formed rectangle.

Reference https://gist.github.com/sgillies/2217756#__geo_interface

pydantic model ephemerista.scenarios.Scenario

The Scenario model.

Fields:
field areas_of_interest: list[Feature[Polygon, dict]] = [] (alias 'areasOfInterest')

List of areas of interest

field assets: list[Asset] = []

List of assets

field auto_discretize: bool = True (alias 'autoDiscretize')

Whether to automatically discretize areas of interest

field channels: list[Channel] = []

List of RF channels

field constellations: list[Constellation] = []

List of constellations

field discretization_method: Literal['rectangles', 'h3'] = 'rectangles' (alias 'discretizationMethod')

Method for discretizing areas of interest

field discretization_resolution: int | float = 1 (alias 'discretizationResolution')

Resolution for discretization (degrees for rectangles, h3 resolution for h3)

field end_time: Time [Required] (alias 'endTime')

End time of the scenario

field frame: ReferenceFrame = ReferenceFrame(abbreviation='ICRF')

Reference frame of the coordinate system

field name: str = 'Scenario'

The name of the scenario

field origin: Origin = Origin(name='Earth')

Origin of the coordinate system

field points_of_interest: list[Feature[Point, dict]] = [] (alias 'pointsOfInterest')

List of points of interest

field scenario_id: Annotated[UUID] [Optional] (alias 'id')

Scenario ID

Constraints:

  • uuid_version = 4

field start_time: Time [Required] (alias 'startTime')

Start time of the scenario

field time_step: float = 60 (alias 'timeStep')

Time step in seconds

classmethod load_from_file(path)

Load a scenario from a JSON file.

Return type:

Self

channel_by_id(channel_id)

Look up a communications channel based on its UUID.

Return type:

Channel

get_discretized_to_original_mapping()

Get mapping from discretized polygon ID to original area ID.

Returns:

Dictionary mapping discretized polygon index to original area index

Return type:

dict[int, int]

get_original_to_discretized_mapping()

Get mapping from original area ID to list of discretized polygon IDs.

Returns:

Dictionary mapping original area index to list of discretized polygon indices

Return type:

dict[int, list[int]]

propagate()

Propagate the state of all assets in the scenario.

Returns:

A collection of all propagated trajectories

Return type:

Ensemble

property all_assets: list[Asset]

All constellation assets and additional assets.

Type:

list[Asset]

property discretized_areas: list[Feature[Polygon, dict]]

Discretized areas of interest.

Type:

list[Feature[Polygon, dict]]

property ground_locations: list[GroundLocation]

All ground locations from areas of interest.

Type:

list[GroundLocation]

property times: list[Time]

Time steps.

Type:

list[Time]

ephemerista.scenarios.polygonize_aoi(aoi_geom_dict, res, min_elevation_deg=0.0)

Polygonize an area of interest using h3.

Parameters:

  • aoi_geom_dict (dict) – A GeoJSON-compatible dict containing a “coordinates” key, usually from a __geo_interface__

  • res (int) – h3 res parameter

  • min_elevation_deg (float) – Minimum elevation in degrees to compute the visibility between a spacecraft and the ground cells

Return type:

list[Feature[Polygon, dict]]

ephemerista.scenarios.polygonize_aoi_rectangles(aoi_geom_dict, vertex_degrees, min_elevation_deg=0.0)

Polygonize an area of interest using rectangles of equal lat/long degrees.

Polygons crossing the antimeridian are divided in two, so no malformed features are created.

Parameters:

  • aoi_geom_dict (dict) – A GeoJSON-compatible dict containing a “coordinates” key, usually from a __geo_interface__ The AOI is the bounding box of this polygon, so the rectangles are arranged as a grid.

  • vertex_degrees (int | float) – Size of the latitude and longitude vertexes in degrees

  • min_elevation_deg (float) – Minimum elevation in degrees to compute the visibility between a spacecraft and the ground cells

Return type:

list[Feature[Polygon, dict]]