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Ground Stations

Ground-based tracking and observation support.

Quick Example

import lox_space as lox

# Define a ground station
gs = lox.GroundLocation(
    origin=lox.Origin("Earth"),
    longitude=0.0,          # radians (Greenwich)
    latitude=0.9,           # radians (~51.5° N)
    altitude=0.0,           # km
)

# Calculate observables for a spacecraft state
obs = gs.observables(state)
print(f"Azimuth: {obs.azimuth():.2f} rad")
print(f"Elevation: {obs.elevation():.2f} rad")
print(f"Range: {obs.range():.1f} km")

# Define elevation mask
mask = lox.ElevationMask.fixed(0.1)  # ~5.7° minimum elevation

# Or variable mask based on azimuth
import numpy as np
azimuth = np.linspace(0, 2*np.pi, 36)
elevation = np.full(36, 0.1)  # same minimum everywhere
mask = lox.ElevationMask.variable(azimuth, elevation)

GroundLocation

Represents a location on the surface of a celestial body.

Parameters:

  • origin

    –

    The central body (e.g., Earth, Moon).

  • longitude

    –

    Geodetic longitude in radians.

  • latitude

    –

    Geodetic latitude in radians.

  • altitude

    –

    Altitude above the reference ellipsoid in km.

Examples:

>>> import math
>>> darmstadt = lox.GroundLocation(
...     lox.Origin("Earth"),
...     longitude=math.radians(8.6512),
...     latitude=math.radians(49.8728),
...     altitude=0.108,
... )

Methods:

  • altitude –

    Return the altitude above the reference ellipsoid in km.

  • latitude –

    Return the geodetic latitude in radians.

  • longitude –

    Return the geodetic longitude in radians.

  • observables –

    Compute observables to a target state.

  • rotation_to_topocentric –

    Return the rotation matrix from body-fixed to topocentric frame.

altitude 

altitude() -> float

Return the altitude above the reference ellipsoid in km.

latitude 

latitude() -> float

Return the geodetic latitude in radians.

longitude 

longitude() -> float

Return the geodetic longitude in radians.

observables 

observables(
    state: State, provider: EOPProvider | None = None, frame: Frame | None = None
) -> Observables

Compute observables to a target state.

rotation_to_topocentric 

rotation_to_topocentric() -> ndarray

Return the rotation matrix from body-fixed to topocentric frame.

ElevationMask

Defines elevation constraints for visibility analysis.

An elevation mask specifies the minimum elevation angle required for visibility at different azimuth angles. Can be either fixed (constant) or variable (azimuth-dependent).

Parameters:

  • azimuth

    –

    Array of azimuth angles in radians (for variable mask).

  • elevation

    –

    Array of minimum elevations in radians (for variable mask).

  • min_elevation

    –

    Fixed minimum elevation in radians.

Examples:

>>> # Fixed elevation mask (5 degrees)
>>> mask = lox.ElevationMask.fixed(5.0 * lox.deg)

>>> # Variable mask based on terrain
>>> mask = lox.ElevationMask.variable(azimuth, elevation)

Methods:

  • azimuth –

    Return the azimuth array (for variable masks only).

  • elevation –

    Return the elevation array (for variable masks only).

  • fixed –

    Create a fixed elevation mask with constant minimum elevation.

  • fixed_elevation –

    Return the fixed elevation value (for fixed masks only).

  • min_elevation –

    Return the minimum elevation at the given azimuth.

  • variable –

    Create a variable elevation mask from azimuth-dependent data.

azimuth 

azimuth() -> list[float] | None

Return the azimuth array (for variable masks only).

elevation 

elevation() -> list[float] | None

Return the elevation array (for variable masks only).

fixed classmethod 

fixed(min_elevation: float) -> Self

Create a fixed elevation mask with constant minimum elevation.

fixed_elevation 

fixed_elevation() -> float | None

Return the fixed elevation value (for fixed masks only).

min_elevation 

min_elevation(azimuth: float) -> float

Return the minimum elevation at the given azimuth.

variable classmethod 

variable(azimuth: ndarray, elevation: ndarray) -> Self

Create a variable elevation mask from azimuth-dependent data.

Observables

Observation data from a ground station to a target.

Parameters:

  • azimuth

    –

    Azimuth angle in radians (measured from north, clockwise).

  • elevation

    –

    Elevation angle in radians (above local horizon).

  • range

    –

    Distance to target in km.

  • range_rate

    –

    Rate of change of range in km/s.

Methods:

  • azimuth –

    Return the azimuth angle in radians.

  • elevation –

    Return the elevation angle in radians.

  • range –

    Return the range (distance) in km.

  • range_rate –

    Return the range rate in km/s.

azimuth 

azimuth() -> float

Return the azimuth angle in radians.

elevation 

elevation() -> float

Return the elevation angle in radians.

range 

range() -> float

Return the range (distance) in km.

range_rate 

range_rate() -> float

Return the range rate in km/s.

Pass

Represents a visibility pass between a ground station and spacecraft.

A Pass contains the visibility window (start and end times) along with observables computed at regular intervals throughout the pass.

Methods:

  • interpolate –

    Interpolate observables at a specific time within the pass.

  • observables –

    Return the observables at each time sample.

  • times –

    Return the time samples during this pass.

  • window –

    Return the visibility window for this pass.

interpolate 

interpolate(time: Time) -> Observables | None

Interpolate observables at a specific time within the pass.

observables 

observables() -> list[Observables]

Return the observables at each time sample.

times 

times() -> list[Time]

Return the time samples during this pass.

window 

window() -> Window

Return the visibility window for this pass.