opengnc.environment package

Submodules

opengnc.environment.density module

Atmospheric density models (Exponential, Harris-Priester, NRLMSISE-00, JB2008).

class opengnc.environment.density.CIRA72

Bases: object

COSPAR International Reference Atmosphere (CIRA) 1972 simplified version.

get_density(r_eci: ndarray, jd: float) → float

Calculate density using log-polynomial fit.

Parameters:

• r_eci (np.ndarray) – ECI position vector (m).

• jd (float) – Julian Date.

Returns:

Atmospheric density ($kg/m^3$).

Return type:

float

class opengnc.environment.density.Exponential(rho0: float = 1.225, h0: float = 0.0, h_scale: float | None = None, **kwargs: Any)

Bases: object

Exponential Atmospheric Density.

Model: $rho = rho_0 expleft(-frac{h - h_0}{H}right)$

Parameters:

• rho0 (float, optional) – Base density at $h_0$ (kg/m^3).

• h0 (float, optional) – Reference altitude (km).

• h_scale (float, optional) – Scale height $H$ (km).

get_density(r_eci: ndarray, jd: float) → float

Calculate local density.

Parameters:

• r_eci (np.ndarray) – ECI position vector (m).

• jd (float) – Julian Date (UT1).

Returns:

Atmospheric density ($kg/m^3$).

Return type:

float

class opengnc.environment.density.HarrisPriester(lag_deg: float = 30.0)

Bases: object

Harris-Priester Diurnal Bulge Model.

Equation: $rho = rho_{min} + (rho_{max} - rho_{min}) cos^n(frac{psi}{2})$

Parameters:

lag_deg (float, optional) – Solar lag angle (degrees). Default 30.0.

get_density(r_eci: ndarray, jd: float) → float

Calculate Harris-Priester interpolated density.

Parameters:

• r_eci (np.ndarray) – ECI position vector (m).

• jd (float) – Julian Date (UT1).

Returns:

Density ($kg/m^3$).

Return type:

float

class opengnc.environment.density.JB2008(space_weather: Any | None = None)

Bases: object

Simplified Jacchia-Bowman 2008 (JB2008) Atmosphere Model.

A high-accuracy model based on Jacchia’s diffusion equations, driven by solar indices (F10.7, S10, M10, etc).

Parameters:

space_weather (Optional[Any], optional) – SpaceWeather model for fetching real-time indices.

get_density(r_eci: ndarray, jd: float) → float

Calculate density using solar-scaled thermospheric approximation.

Parameters:

• r_eci (np.ndarray) – ECI position vector (m).

• jd (float) – Julian Date (UT1).

Returns:

Atmospheric density ($kg/m^3$).

Return type:

float

class opengnc.environment.density.NRLMSISE00

Bases: object

NRLMSISE-00 high-fidelity atmospheric density model.

The standard empirical model of the Earth’s atmosphere from ground to space. Accounts for solar activity, geomagnetic storms, and seasonal variations.

Notes

Requires the pymsis package.

get_density(r_eci: ndarray, date: datetime) → float

Get total mass density using NRLMSISE-00.

Parameters:

• r_eci (np.ndarray) – ECI position vector (m).

• date (datetime) – Current UTC time.

Returns:

Atmospheric density ($kg/m^3$).

Return type:

float

opengnc.environment.mag_field module

Earth magnetic field models (IGRF, WMM, Tilted Dipole).

opengnc.environment.mag_field.igrf_field(lat: float, lon: float, alt: float, time: datetime | float) → ndarray

Get the International Geomagnetic Reference Field (IGRF) vector.

Parameters:

• lat (float) – Geodetic latitude (deg).

• lon (float) – Geodetic longitude (deg).

• alt (float) – Altitude above the WGS84 ellipsoid (km).

• time (datetime.datetime or float) – Time for IGRF calculation. Decimal year preferred for float.

Returns:

Magnetic field vector $[B_{North}, B_{East}, B_{Down}]$ (nT).

Return type:

np.ndarray

Raises:

ImportError – If ppigrf dependency is not installed.

opengnc.environment.mag_field.tilted_dipole_field(r_ecef: ndarray) → ndarray

Tilted Dipole Geomagnetic Approximation.

A simplified model useful for fast orbit propagation. Approximates Earth’s field as a dipole tilted relative to the geographic poles.

Equation: $mathbf{B} = frac{mu_0}{4pi} frac{1}{r^3} [3(mathbf{m} cdot hat{mathbf{r}})hat{mathbf{r}} - mathbf{m}]$

Parameters:

r_ecef (np.ndarray) – Position vector in ECEF frame (m).

Returns:

Magnetic field vector in ECEF frame (T).

Return type:

np.ndarray

opengnc.environment.mag_field.wmm_field(lat: float, lon: float, alt: float, date: datetime | float) → ndarray

Get the World Magnetic Model (WMM) field vector.

Proxied via IGRF in this implementation for GNC simulation balance.

Parameters:

• lat (float) – Geodetic latitude (deg).

• lon (float) – Geodetic longitude (deg).

• alt (float) – Altitude (km).

• date (datetime.datetime or float) – Date for model calculation.

Returns:

Magnetic field vector $[B_{North}, B_{East}, B_{Down}]$ (nT).

Return type:

np.ndarray

opengnc.environment.moon module

Simplified Lunar Ephemeris Model for position calculation.

class opengnc.environment.moon.Moon

Bases: object

Lunar Ephemeris Model (Vallado 3.5).

Provides the Moon’s position vector in the Earth-Centered Inertial (ECI) frame.

Calculation (Fundamental Arguments): $L$ = Mean longitude, $M’$ = Moon mean anomaly, $M$ = Sun mean anomaly, $D$ = Mean elongation, $u$ = Mean latitude.

Parameters:

None

calculate_moon_eci(jd: float) → ndarray

Calculate Moon vector in ECI.

Parameters:

jd (float) – Julian Date (UT1).

Returns:

Moon position vector $[x, y, z]$ (m).

Return type:

np.ndarray

opengnc.environment.multibody_dynamics module

Circular Restricted Three-Body Problem (CR3BP) dynamics.

class opengnc.environment.multibody_dynamics.CR3BP(mu: float)

Bases: object

Circular Restricted Three-Body Problem Dynamics.

Models the motion of a negligible mass under the influence of two massive bodies (primaries) in a circular orbit about their barycenter.

Parameters:

mu (float) – Mass parameter $mu = m_2 / (m_1 + m_2)$.

calculate_jacobi_constant(state: ndarray) → float

Calculate the Jacobi constant (Integral of motion).

$C = (x^2 + y^2) + 2frac{1-mu}{r_1} + 2frac{mu}{r_2} - (vx^2 + vy^2 + vz^2)$

Parameters:

state (np.ndarray) – Current state.

Returns:

Jacobi constant value.

Return type:

float

get_dynamics(t: float, state: ndarray) → ndarray

Calculate state derivatives in the rotating frame.

Parameters:

• t (float) – Time (normalized).

• state (np.ndarray) – Current state $[x, y, z, vx, vy, vz]$.

Returns:

Derivative vector $[dot{x}, dot{y}, dot{z}, dot{vx}, dot{vy}, dot{vz}]$.

Return type:

np.ndarray

opengnc.environment.radiation module

Radiation environment models for TID and SEU rates estimation.

class opengnc.environment.radiation.RadiationModel

Bases: object

Parametric Space Radiation Environment Models.

Estimates Total Ionizing Dose (TID) and Single Event Upset (SEU) rates for spacecraft electronic components in Low Earth Orbit (LEO).

estimate_seu_rate(altitude_km: float, device_cross_section: float = 1e-12) → float

Estimate Single Event Upset (SEU) rate from proton flux.

Parameters:

• altitude_km (float) – Orbit altitude (km).

• device_cross_section (float, optional) – Device sensitive area ($cm^2/bit$). Default 1e-12.

Returns:

Estimated SEUs per bit-day.

Return type:

float

estimate_tid(altitude_km: float, inclination_deg: float, duration_days: float) → float

Estimate cumulative Total Ionizing Dose (TID).

Uses a parametric fit for LEO orbits assuming 2.5 mm Aluminum shielding.

Parameters:

• altitude_km (float) – Orbit altitude (km).

• inclination_deg (float) – Orbit inclination (deg).

• duration_days (float) – Mission duration (days).

Returns:

Estimated TID in kRad(Si).

Return type:

float

opengnc.environment.solar module

Solar position models based on Julian Date.

class opengnc.environment.solar.Sun

Bases: object

Solar Position Model (Astronomical Almanac).

Provides the Sun’s position vector in the Earth-Centered Inertial (ECI) frame (J2000).

Calculation: $lambda_{ecl} = q + 1.915 sin(g) + 0.020 sin(2g)$ where $q$ is mean longitude and $g$ is mean anomaly.

Parameters:

None

calculate_sun_eci(jd: float) → ndarray

Calculate Sun vector in ECI J2000.

Parameters:

jd (float) – Julian Date (UT1).

Returns:

Sun position $[x, y, z]$ (m).

Return type:

np.ndarray

opengnc.environment.space_weather module

Space weather index management (F10.7, Ap, Kp) for disturbance models.

class opengnc.environment.space_weather.SpaceWeather(f107: float = 150.0, f107_avg: float = 150.0, ap: float = 15.0)

Bases: object

Solar and Geomagnetic Activity Indices Manager.

Coordinates F10.7 (solar flux) and Ap/Kp (geomagnetic) indices used by thermospheric and radiation models.

Parameters:

• f107 (float, optional) – Daily solar flux index at 10.7cm (sfu). Default 150.0.

• f107_avg (float, optional) – 81-day centered mean solar flux (sfu). Default 150.0.

• ap (float, optional) – Planetary equivalent amplitude index (geomagnetic). Default 15.0.

get_indices(date: Any | None = None) → dict[str, float]

Retrieve indices for a given epoch.

Parameters:

date (Optional[Any], optional) – Target epoch. Currently returns static values.

Returns:

Indices dictionary.

Return type:

Dict[str, float]

set_solar_flux(f107: float, f107_avg: float | None = None) → None

Update local solar flux parameters.

Parameters:

• f107 (float) – Daily solar flux (sfu).

• f107_avg (Optional[float], optional) – Average solar flux. Defaults to f107 if None.

opengnc.environment.thermal module

Spacecraft thermal environment flux models (Solar, Albedo, Earth IR).

class opengnc.environment.thermal.ThermalEnvironment(albedo_coeff: float = 0.3, earth_ir: float = 230.0)

Bases: object

Spacecraft External Thermal Environment Models.

Calculates heat fluxes from direct solar radiation, planetary albedo, and outgoing longwave radiation (Earth IR).

Parameters:

• albedo_coeff (float, optional) – Planetary mean spherical albedo [0, 1]. Default 0.3.

• earth_ir (float, optional) – Mean outgoing longwave radiation (W/m^2). Default 230.0.

get_albedo_flux(r_sat: ndarray, r_sun: ndarray) → float

Calculate planet-reflected solar flux (Albedo).

Uses a Lambertian reflection model.

Parameters:

• r_sat (np.ndarray) – Satellite ECI position (m).

• r_sun (np.ndarray) – Sun ECI position (m).

Returns:

Albedo flux on a nadir-facing surface ($W/m^2$).

Return type:

float

get_earth_ir_flux() → float

Get standard Earth IR flux.

Returns:

Planetary IR flux ($W/m^2$).

Return type:

float

get_solar_flux(distance_au: float = 1.0) → float

Calculate direct solar flux.

Equation: $F_{sun} = S / d^2$

Parameters:

distance_au (float, optional) – Sun-spacecraft distance (AU). Default 1.0.

Returns:

Solar flux ($W/m^2$).

Return type:

float

opengnc.environment.wind module

Atmospheric wind and earth co-rotation modeling.

class opengnc.environment.wind.AtmosphereCoRotation(omega_e: float = 7.2921151467e-05)

Bases: object

Atmospheric Wind Model (Strict Co-Rotation).

Assumes that the atmosphere rotates perfectly in sync with the planet’s Earth-Centered Earth-Fixed (ECEF) frame.

Parameters:

omega_e (float, optional) – Planetary angular rate (rad/s). Default Earth WGS84 rate.

get_relative_velocity(r_eci: ndarray, v_eci: ndarray, jd: float) → ndarray

Calculate spacecraft velocity relative to the atmosphere (Airspeed).

Equation: $mathbf{v}_{rel} = mathbf{v}_{sc} - mathbf{v}_w$

Parameters:

• r_eci (np.ndarray) – ECI position (m).

• v_eci (np.ndarray) – ECI spacecraft velocity (m/s).

• jd (float) – Julian Date.

Returns:

Relative velocity vector (m/s).

Return type:

np.ndarray

get_wind_velocity(r_eci: ndarray, jd: float) → ndarray

Calculate local wind velocity vector in ECI.

Equation: $mathbf{v}_w = boldsymbol{omega}_E times mathbf{r}_{eci}$

Parameters:

• r_eci (np.ndarray) – ECI position vector (m).

• jd (float) – Julian Date.

Returns:

Wind velocity vector (m/s).

Return type:

np.ndarray

Module contents