Atmospheric Propagation (ITU-R)

ITU-R P-series atmospheric propagation models for computing attenuation on Earth-to-space radio paths. Based on the ITU-Rpy library.

Quick Start

Compute the total atmospheric attenuation for a ground station in Madrid receiving at 14.25 GHz from a satellite at 30° elevation:

import lox_space as lox

losses = lox.EnvironmentalLosses(
    lat=40.4 * lox.deg,
    lon=-3.7 * lox.deg,
    frequency=14.25 * lox.GHz,
    elevation=30.0 * lox.deg,
    probability=0.01,       # exceeded 0.01% of the year
    diameter=1.2 * lox.m,   # antenna diameter
)

print(f"Rain:          {losses.rain}")
print(f"Gaseous:       {losses.gaseous}")
print(f"Cloud:         {losses.cloud}")
print(f"Scintillation: {losses.scintillation}")
print(f"Total:         {losses.atmospheric}")

The same computation is also available as a free-standing function:

losses = lox.atmospheric_attenuation_slant_path(
    lat=40.4 * lox.deg, lon=-3.7 * lox.deg,
    frequency=14.25 * lox.GHz, elevation=30.0 * lox.deg,
    probability=0.01, diameter=1.2 * lox.m,
)

For link budgets with known loss values, use EnvironmentalLosses.from_values or EnvironmentalLosses.none:

losses = lox.EnvironmentalLosses.from_values(rain=2.0 * lox.dB, gaseous=0.5 * lox.dB)
losses = lox.EnvironmentalLosses.none()

The result plugs directly into LinkStats.calculate for link budget analysis.

Individual Models

Each ITU-R recommendation is also available as a standalone function.

Rain Attenuation (P.618)

a_rain = lox.rain_attenuation(
    lat=40.4 * lox.deg,
    lon=-3.7 * lox.deg,
    frequency=14.25 * lox.GHz,
    elevation=30.0 * lox.deg,
    probability=0.01,
)

Gaseous Attenuation (P.676)

a_oxygen, a_water = lox.gaseous_attenuation_slant_path(
    frequency=14.25 * lox.GHz,
    elevation=30.0 * lox.deg,
    pressure=1013.25 * lox.hPa,
    rho=7.5,                      # water vapour density (g/m³)
    temperature=288.15 * lox.K,
)

Cloud Attenuation (P.840)

a_cloud = lox.cloud_attenuation(
    lat=40.4 * lox.deg,
    lon=-3.7 * lox.deg,
    elevation=30.0 * lox.deg,
    frequency=14.25 * lox.GHz,
    probability=1.0,
)

Scintillation (P.618)

a_scint = lox.scintillation_attenuation(
    frequency=14.25 * lox.GHz,
    elevation=30.0 * lox.deg,
    probability=0.01,
    diameter=1.2 * lox.m,
    lat=40.4 * lox.deg,
    lon=-3.7 * lox.deg,
)

Specific Rain Attenuation (P.838)

gamma_r = lox.rain_specific_attenuation(
    rain_rate=25.0,               # mm/h
    frequency=14.25 * lox.GHz,
    elevation=30.0 * lox.deg,
)

Geophysical Data Lookups

Topographic Altitude (P.1511)

alt = lox.topographic_altitude(lat=27.99 * lox.deg, lon=86.93 * lox.deg)
print(f"Altitude: {alt.to_kilometers():.1f} km")

Surface Temperature (P.1510)

t = lox.surface_mean_temperature(lat=0.0 * lox.deg, lon=0.0 * lox.deg)
print(f"Temperature: {t.to_kelvin():.1f} K")

Rainfall Rate (P.837)

r = lox.rainfall_rate(lat=40.4 * lox.deg, lon=-3.7 * lox.deg, probability=0.01)
print(f"Rainfall rate: {r:.1f} mm/h")

Rain Height (P.839)

h = lox.rain_height(lat=40.4 * lox.deg, lon=-3.7 * lox.deg)
print(f"Rain height: {h.to_kilometers():.1f} km")

Link Budget Integration

EnvironmentalLosses can be passed directly to LinkStats.calculate:

losses = lox.EnvironmentalLosses(
    lat=40.4 * lox.deg,
    lon=-3.7 * lox.deg,
    frequency=29.0 * lox.GHz,
    elevation=30.0 * lox.deg,
    probability=0.01,
    diameter=0.6 * lox.m,
)

stats = lox.LinkStats.calculate(
    tx_system=tx,
    rx_system=rx,
    channel=channel,
    range=1000.0 * lox.km,
    tx_angle=0.0 * lox.rad,
    rx_angle=0.0 * lox.rad,
    losses=losses,
)

Data Files

Grid-based models (P.1511, P.1510, P.836, P.837, P.839, P.840, P.453) require reference data from the ITU. This data is automatically downloaded from PyPI and converted during the build process. No manual setup is needed.

Implemented Recommendations

Recommendation	Description
P.453-13	Radio refractive index
P.618-14	Earth-space propagation (rain, scintillation, XPD)
P.676-13	Gaseous attenuation (O₂ + H₂O)
P.835-6	Reference standard atmospheres
P.836-6	Water vapour surface density
P.837-7	Rainfall rate
P.838-3	Specific rain attenuation
P.839-4	Rain height
P.840-9	Cloud and fog attenuation
P.1510-1	Surface temperature
P.1511-2	Topographic altitude

atmospheric_attenuation_slant_path `builtin`

atmospheric_attenuation_slant_path(
    lat: Angle,
    lon: Angle,
    frequency: Frequency,
    elevation: Angle,
    probability: float,
    diameter: Distance,
    polarisation_tilt: Angle | None = None,
) -> EnvironmentalLosses

Computes atmospheric attenuation on a slant path, returning individual contributions as an EnvironmentalLosses object.

Parameters:

lat
(Angle) –

Latitude.
lon
(Angle) –

Longitude.
frequency
(Frequency) –

Frequency.
elevation
(Angle) –

Elevation angle.
probability
(float) –

Exceedance probability (% of average year).
diameter
(Distance) –

Physical antenna diameter.
polarisation_tilt
(Angle | None, default: None ) –

Polarisation tilt angle (default 45° for circular).

Returns:

EnvironmentalLosses –

EnvironmentalLosses with rain, gaseous, cloud, scintillation, and
EnvironmentalLosses –

depolarization fields populated.

rain_attenuation `builtin`

rain_attenuation(
    lat: Angle,
    lon: Angle,
    frequency: Frequency,
    elevation: Angle,
    probability: float,
    polarisation_tilt: Angle | None = None,
) -> Decibel

Computes rain attenuation exceeded for a given probability (P.618-13).

Parameters:

lat
(Angle) –

Latitude.
lon
(Angle) –

Longitude.
frequency
(Frequency) –

Frequency.
elevation
(Angle) –

Elevation angle.
probability
(float) –

Exceedance probability (% of average year).
polarisation_tilt
(Angle | None, default: None ) –

Polarisation tilt angle (default 45° for circular).

Returns:

Decibel –

Rain attenuation.

gaseous_attenuation_slant_path `builtin`

gaseous_attenuation_slant_path(
    frequency: Frequency,
    elevation: Angle,
    pressure: Pressure,
    rho: float,
    temperature: Temperature,
) -> tuple[Decibel, Decibel]

Computes gaseous attenuation on a slant path (P.676-12 approximate method).

Parameters:

frequency
(Frequency) –

Frequency.
elevation
(Angle) –

Elevation angle.
pressure
(Pressure) –

Surface pressure.
rho
(float) –

Surface water vapour density in g/m³.
temperature
(Temperature) –

Surface temperature.

Returns:

tuple[Decibel, Decibel] –

Tuple of (oxygen attenuation, water vapour attenuation).

cloud_attenuation `builtin`

cloud_attenuation(
    lat: Angle, lon: Angle, elevation: Angle, frequency: Frequency, probability: float
) -> Decibel

Computes cloud attenuation on a slant path (P.840-8).

Parameters:

lat
(Angle) –

Latitude.
lon
(Angle) –

Longitude.
elevation
(Angle) –

Elevation angle.
frequency
(Frequency) –

Frequency.
probability
(float) –

Exceedance probability (% of average year).

Returns:

Decibel –

Cloud attenuation.

scintillation_attenuation `builtin`

scintillation_attenuation(
    frequency: Frequency,
    elevation: Angle,
    probability: float,
    diameter: Distance,
    eta: float = 0.5,
    lat: Angle | None = None,
    lon: Angle | None = None,
) -> Decibel

Computes tropospheric scintillation fade depth exceeded for a given probability (P.618-13).

Parameters:

frequency
(Frequency) –

Frequency.
elevation
(Angle) –

Elevation angle.
probability
(float) –

Exceedance probability (% of average year).
diameter
(Distance) –

Physical antenna diameter.
eta
(float, default: 0.5 ) –

Antenna efficiency (default 0.5).
lat
(Angle | None, default: None ) –

Latitude (for N_wet lookup).
lon
(Angle | None, default: None ) –

Longitude (for N_wet lookup).

Returns:

Decibel –

Scintillation attenuation.

rain_specific_attenuation `builtin`

rain_specific_attenuation(
    rain_rate: float,
    frequency: Frequency,
    elevation: Angle,
    polarisation_tilt: Angle | None = None,
) -> float

Computes the specific attenuation from rain (P.838-3).

Parameters:

rain_rate
(float) –

Rainfall rate in mm/h.
frequency
(Frequency) –

Frequency.
elevation
(Angle) –

Elevation angle.
polarisation_tilt
(Angle | None, default: None ) –

Polarisation tilt angle (default 45° for circular).

Returns:

float –

Specific rain attenuation in dB/km.

topographic_altitude `builtin`

topographic_altitude(lat: Angle, lon: Angle) -> Distance

Returns the topographic altitude at the given location (P.1511-2).

Parameters:

lat
(Angle) –

Latitude.
lon
(Angle) –

Longitude.

Returns:

Distance –

Altitude above mean sea level.

surface_mean_temperature `builtin`

surface_mean_temperature(lat: Angle, lon: Angle) -> Temperature

Returns the annual mean surface temperature at the given location (P.1510-1).

Parameters:

lat
(Angle) –

Latitude.
lon
(Angle) –

Longitude.

Returns:

Temperature –

Temperature.

rainfall_rate `builtin`

rainfall_rate(lat: Angle, lon: Angle, probability: float) -> float

Returns the rainfall rate exceeded for a given probability (P.837-7).

Parameters:

lat
(Angle) –

Latitude.
lon
(Angle) –

Longitude.
probability
(float) –

Exceedance probability (% of average year).

Returns:

float –

Rainfall rate in mm/h.

rain_height `builtin`

rain_height(lat: Angle, lon: Angle) -> Distance

Returns the mean annual rain height at the given location (P.839-4).

Parameters:

lat
(Angle) –

Latitude.
lon
(Angle) –

Longitude.

Returns:

Distance –

Rain height.

Atmospheric Propagation (ITU-R)

Quick Start

Individual Models

Rain Attenuation (P.618)

Gaseous Attenuation (P.676)

Cloud Attenuation (P.840)

Scintillation (P.618)

Specific Rain Attenuation (P.838)

Geophysical Data Lookups

Topographic Altitude (P.1511)

Surface Temperature (P.1510)

Rainfall Rate (P.837)

Rain Height (P.839)

Link Budget Integration

Data Files

Implemented Recommendations

atmospheric_attenuation_slant_path builtin

lat

lon

frequency

elevation

probability

diameter

polarisation_tilt

rain_attenuation builtin

lat

lon

frequency

elevation

probability

polarisation_tilt

gaseous_attenuation_slant_path builtin

frequency

elevation

pressure

rho

temperature

cloud_attenuation builtin

lat

lon

elevation

frequency

probability

scintillation_attenuation builtin

frequency

elevation

probability

diameter

eta

lat

lon

rain_specific_attenuation builtin

rain_rate

frequency

elevation

polarisation_tilt

topographic_altitude builtin

lat

lon

surface_mean_temperature builtin

lat

lon

rainfall_rate builtin

lat

lon

probability

rain_height builtin

lat

lon

atmospheric_attenuation_slant_path `builtin`

`lat`

`lon`

`frequency`

`elevation`

`probability`

`diameter`

`polarisation_tilt`

rain_attenuation `builtin`

`lat`

`lon`

`frequency`

`elevation`

`probability`

`polarisation_tilt`

gaseous_attenuation_slant_path `builtin`

`frequency`

`elevation`

`pressure`

`rho`

`temperature`

cloud_attenuation `builtin`

`lat`

`lon`

`elevation`

`frequency`

`probability`

scintillation_attenuation `builtin`

`frequency`

`elevation`

`probability`

`diameter`

`eta`

`lat`

`lon`

rain_specific_attenuation `builtin`

`rain_rate`

`frequency`

`elevation`

`polarisation_tilt`

topographic_altitude `builtin`

`lat`

`lon`

surface_mean_temperature `builtin`

`lat`

`lon`

rainfall_rate `builtin`

`lat`

`lon`

`probability`

rain_height `builtin`

`lat`

`lon`