Orbis.Atmosphere (Orbis v0.8.0)

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Atmospheric density via the NRLMSISE-00 empirical model.

NRLMSISE-00 computes total mass density and temperature from the surface to the lower exosphere (~1000 km). It is the standard model used for satellite drag prediction.

Quick example

position = %{latitude: 0.0, longitude: 0.0, altitude_km: 400.0}
{:ok, result} = Orbis.Atmosphere.density(position, ~U[2024-06-20 12:00:00Z])
result.density    # kg/m^3 (e.g., ~3e-12 at ISS altitude)
result.temperature # K

Solar/geomagnetic indices

The model depends on space weather conditions. You can supply these via the :f107, :f107a, and :ap options. If omitted, moderate defaults are used (F10.7 = F10.7A = 150.0, Ap = 4.0).

For operational use, fetch current indices from NOAA/SWPC.

Summary

Functions

density(position, datetime, opts \\ [])

Compute atmospheric density and temperature at a given position and time.

Functions

density(position, datetime, opts \\ [])

Compute atmospheric density and temperature at a given position and time.

Parameters

  • position - geodetic position as %{latitude: deg, longitude: deg, altitude_km: km}
  • datetime - observation time as DateTime or {{y,m,d},{h,m,s}} tuple
  • opts - keyword list of optional space weather indices:
    • :f107 - daily 10.7 cm solar radio flux (default 150.0)
    • :f107a - 81-day average of F10.7 (default 150.0)
    • :ap - daily geomagnetic Ap index (default 4.0)

Returns

{:ok, %{density: kg_per_m3, temperature: kelvin}} or {:error, reason}.

Examples

# ISS altitude with default solar activity
pos = %{latitude: 28.5, longitude: -80.6, altitude_km: 408.0}
{:ok, result} = Orbis.Atmosphere.density(pos, ~U[2024-06-20 12:00:00Z])

# With explicit solar indices
{:ok, result} = Orbis.Atmosphere.density(pos, ~U[2024-06-20 12:00:00Z],
  f107: 180.0, f107a: 160.0, ap: 15.0)