Library

Documentation for AstroForceModels.jl.

AstroForceModels.AbstractSatelliteDragModel — Type

Abstract satellite drag model to help compute drag forces.

AstroForceModels.AbstractSatelliteSRPModel — Type

Abstract satellite drag model to help compute drag forces.

AstroForceModels.CannonballFixedDrag — Type

Cannonball Fixed Drag Model struct Contains information to compute the ballistic coefficient of a cannonball drag model with a fixed ballistic coefficient.

Fields

radius::Number: The radius of the spacecraft.
mass::Number: The mass of the spacecraft.
drag_coeff::Number: The drag coefficient of the spacecraft.
ballistic_coeff::Number: The fixed ballistic coefficient to use.

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AstroForceModels.CannonballFixedDrag — Method

CannonballFixedDrag(radius::Number, mass::Number, drag_coeff::Number)

Constructor for a fixed cannonball ballistic coefficient drag model.

The ballistic coefficient is computed with the following equation:

            BC = CD * area/mass

where area is the 2D projection of a sphere

            area = π * r^2

Arguments

radius::Number: The radius of the spacecraft.
mass::Number: The mass of the spacecraft.
drag_coeff::Number: The drag coefficient of the spacecraft.

Returns

drag_model::CannonballFixedDrag: A fixed ballistic coefficient drag model.

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AstroForceModels.CannonballFixedDrag — Method

CannonballFixedDrag(ballistic_coeff::Number)

Constructor for a fixed ballistic coefficient drag model.

Arguments

ballistic_coeff::Number: The fixed ballistic coefficient to use.

Returns

drag_model::CannonballFixedDrag: A fixed ballistic coefficient drag model.

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AstroForceModels.CannonballFixedSRP — Type

Cannonball Fixed SRP Model struct Contains information to compute the reflectivity coefficient of a cannonball drag model with a fixed reflectivity coefficient.

Fields

radius::Number: The radius of the spacecraft.
mass::Number: The mass of the spacecraft.
reflectivity_coeff::Number: The reflectivity coefficient of the spacecraft.
reflectivity_ballistic_coeff::Number: The fixed ballistic coefficient to use.

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AstroForceModels.CannonballFixedSRP — Method

CannonballFixedSRP(radius::Number, mass::Number, drag_coeff::Number)

Constructor for a fixed cannonball ballistic coefficient SRP model.

The ballistic coefficient is computed with the following equation:

            RC = CD * area/mass

where area is the 2D projection of a sphere

            area = π * r^2

Arguments

radius::Number: The radius of the spacecraft.
mass::Number: The mass of the spacecraft.
reflectivity_coeff::Number: The reflectivity coefficient of the spacecraft.

Returns

srp_model::CannonballFixedSRP`: A fixed ballistic coefficient SRP model.

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AstroForceModels.CannonballFixedSRP — Method

CannonballFixedSRP(ballistic_coeff::Number)

Constructor for a fixed ballistic coefficient SRP model.

Arguments

ballistic_coeff::Number: The fixed ballistic coefficient to use.

Returns

srp_model::CannonballFixedDrag: A fixed ballistic coefficient SRP model.

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AstroForceModels.CelestialBody — Type

Creates a CelestialBody Object from a name Available: {Sun, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto,

Fields: -CelestialBody{T<:Number}: PlanetBody Object with Fields: - name::String: Name of Object - central_body::String: Name of Central Body Being Orbited - jpl_code::Int: NAIF ID Code - μ::T: Graviational Parameter [km/s] - Req::T: Equatorial Radius [km]

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AstroForceModels.DragAstroModel — Type

Drag Astro Model struct Contains information to compute the acceleration of a drag force on a spacecraft.

Fields

satellite_drag_model::AbstractSatelliteDragModel: The satellite drag model for computing the ballistic coefficient.
atmosphere_model::Symbol: The atmospheric model for computing the density.
eop_data::EopIau1980: Earth orientation parameters to help compute the density with the atmospheric model.

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AstroForceModels.GravityHarmonicsAstroModel — Type

Gravitational Harmonics Astro Model struct Contains information to compute the acceleration of a Gravitational Harmonics Model acting on a spacecraft.

Fields

gravity_model::AbstractGravityModel: The gravitational potential model and coefficient data.
eop_data::Union{EopIau1980,EopIau2000A}: The data compute the Earth's orientation.
order::Int: The maximum order to compute the graviational potential to, a value of -1 compute the maximum order of the supplied model. (Default=-1)
degree::Int: The maximum degree to compute the graviational potential to, a value of -1 compute the maximum degree of the supplied model. (Default=-1)

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AstroForceModels.KeplerianGravityAstroModel — Type

Gravitational Keplerian Astro Model struct Contains information to compute the acceleration of a Gravitational Harmonics Model acting on a spacecraft.

Fields

μ::Number: The gravitational potential constant of the central body.

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AstroForceModels.RelativityModel — Type

Relativity Astro Model struct Contains information to compute the acceleration of relativity acting on a spacecraft.

Fields

central_body::ThirdBodyModel: The data to compute the central body's graviational parameter.
sun_body::ThirdBodyModel: The data to compute the Sun's position, velocity, and graviational parameter.
eop_data::Union{EopIau1980,EopIau2000A}: Earth Orientation Parameter data.
c::Number: The speed of light [km/s].
γ::Number: Post-Newtonian Parameterization parameter. γ=1 in General Relativity.
β::Number: Post-Newtonian Parameterization parameter. β=1 in General Relativity.
schwartzchild_effect::Bool: Include the Schwartzchild relativity effect.
lense_thirring_effect::Bool: Include the Lense Thirring relativity effect.
de_Sitter_effect::Bool: Include the De Sitter relativity effect.

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AstroForceModels.SRPAstroModel — Type

SRP Astro Model struct Contains information to compute the acceleration of a SRP a spacecraft.

Fields

satellite_srp_model::AbstractSatelliteDragModel: The satellite srp model for computing the ballistic coefficient.
sun_data::ThirdBodyModel: The data to compute the Sun's position.

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AstroForceModels.StateDragModel — Type

State Drag Model struct Empty struct used for when the simulation state includes the ballistic coefficient.

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AstroForceModels.StateSRPModel — Type

State SRP Model struct Empty struct used for when the simulation state includes the reflectivity ballistic coefficient.

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AstroForceModels.ThirdBodyModel — Type

Third Body Model Astro Model struct Contains information to compute the acceleration of a third body force acting on a spacecraft.

Fields

body::CelestialBody: Celestial body acting on the craft.
ephem_type::AbstractEphemerisType: Ephemeris type used to compute body's position. Options are currently Vallado().

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AstroForceModels.ThirdBodyModel — Method

Convenience to compute the ephemeris position of a CelestialBody in a ThirdBodyModel Wraps get_position().

Arguments

time::Number: Current time of the simulation in seconds.

Returns

body_position: SVector{3}: The 3-dimensional third body position in the J2000 frame.

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AstroForceModels.acceleration — Method

acceleration(u::AbstractArray, p::ComponentVector, t::Number, drag_model::DragAstroModel)

Computes the drag acceleration acting on a spacecraft given a drag model and current state and parameters of an object.

Arguments

u::AbstractArray: Current State of the simulation.
p::ComponentVector: Current parameters of the simulation.
t::Number: Current time of the simulation.
drag_model::DragAstroModel: Drag model struct containing the relevant information to compute the acceleration.

Returns

acceleration: SVector{3}: The 3-dimensional drag acceleration acting on the spacecraft.

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AstroForceModels.acceleration — Method

acceleration(u::AbstractArray, p::ComponentVector, t::Number, grav_model::GravityHarmonicsAstroModel)

Computes the gravitational acceleration acting on a spacecraft given a gravity model and current state and parameters of an object.

Arguments

u::AbstractArray: Current State of the simulation.
p::ComponentVector: Current parameters of the simulation.
t::Number: Current time of the simulation.
gravity_model::GravityHarmonicsAstroModel: Gravity model struct containing the relevant information to compute the acceleration.

Returns

acceleration: SVector{3}: The 3-dimensional gravity acceleration acting on the spacecraft.

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AstroForceModels.acceleration — Method

acceleration(u::AbstractArray, p::ComponentVector, t::Number, grav_model::KeplerianGravityAstroModel)

Computes the gravitational acceleration acting on a spacecraft given a gravity model and current state and parameters of an object.

Arguments

u::AbstractArray: Current State of the simulation.
p::ComponentVector: Current parameters of the simulation.
t::Number: Current time of the simulation.
gravity_model::KeplerianGravityAstroModel: Gravity model struct containing the relevant information to compute the acceleration.

Returns

acceleration: SVector{3}: The 3-dimensional gravity acceleration acting on the spacecraft.

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AstroForceModels.acceleration — Method

acceleration(u::AbstractArray, p::ComponentVector, t::Number, srp_model::SRPAstroModel)

Computes the srp acceleration acting on a spacecraft given a srp model and current state and parameters of an object.

Arguments

u::AbstractArray: Current State of the simulation.
p::ComponentVector: Current parameters of the simulation.
t::Number: Current time of the simulation.
srp_model::SRPAstroModel: SRP model struct containing the relevant information to compute the acceleration.

Returns

acceleration: SVector{3}: The 3-dimensional srp acceleration acting on the spacecraft.

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AstroForceModels.acceleration — Method

acceleration(u::AbstractArray, p::ComponentVector, t::Number, third_body_model::ThirdBodyModel)

Computes the drag acceleration acting on a spacecraft given a drag model and current state and parameters of an object.

Arguments

u::AbstractArray: Current State of the simulation.
p::ComponentVector: Current parameters of the simulation.
t::Number: Current time of the simulation.
third_body_model::ThirdBodyModel: Third body model struct containing the relevant information to compute the acceleration.

Returns

acceleration: SVector{3}: The 3-dimensional srp acceleration acting on the spacecraft.

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AstroForceModels.acceleration — Method

acceleration(u::AbstractArray, p::ComponentVector, t::Number, relativity_model::RelativityModel)

Computes the srp acceleration acting on a spacecraft given a srp model and current state and parameters of an object.

Arguments

u::AbstractArray: Current State of the simulation.
p::ComponentVector: Current parameters of the simulation.
t::Number: Current time of the simulation.
relativity_model::RelativityModel: Relativity model struct containing the relevant information to compute the acceleration.

Returns

acceleration: SVector{3}: The 3-dimensional relativity acceleration acting on the spacecraft.

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AstroForceModels.ballistic_coefficient — Method

ballistic_coefficient( u::AbstractArray, p::ComponentVector, t::Number, model::CannonballFixedDrag)

Returns the ballistic coefficient for a drag model given the model and current state of the simulation.

Arguments

- `u::AbstractArray`: The current state of the simulation.
- `p::ComponentVector`: The parameters of the simulation.
- `t::Number`: The current time of the simulation.
- `model::CannonballFixedDrag`: Drag model for the spacecraft.

Returns

-`ballistic_coeff::Number`: The current ballistic coefficient of the spacecraft.

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AstroForceModels.ballistic_coefficient — Method

ballistic_coefficient( u::AbstractArray, p::ComponentVector, t::Number, model::StateDragModel)

Returns the ballistic coefficient for a drag model given the model and current state of the simulation.

Arguments

- `u::AbstractArray`: The current state of the simulation.
- `p::ComponentVector`: The parameters of the simulation.
- `t::Number`: The current time of the simulation.
- `model::StateDragModel`: The drag model for the spacecraft.

Returns

-`ballistic_coeff::Number`: The current ballistic coefficient of the spacecraft.

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AstroForceModels.build_dynamics_model — Method

build_dynamics_model(u::AbstractArray, p::ComponentVector, t::Number, models::AbstractArray{AbstractAstroForceModel})

Convenience funcction to compute the overall acceleration acting on the spacecraft.

Arguments

u::AbstractArray: Current State of the simulation.
p::ComponentVector: Current parameters of the simulation.
t::Number: Current time of the simulation.
models::AbstractArray{AbstractAstroForceModel}: Array of acceleration models acting on the spacecraft

Returns

acceleration: SVector{3}: The 3-dimensional drag acceleration acting on the spacecraft.

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AstroForceModels.compute_density — Function

compute_density(JD::Number, u::AbstractArray, eop_data::EopIau1980, AtmosphereType::AtmosphericModelType)

Computes the atmospheric density at a point given the date, position, eop_data, and atmosphere type

Arguments

JD::Number: The current time of the simulation in Julian days.
u::AbstractArray: The current state of the simulation.
eop_data::EopIau1980: The earth orientation parameters.
AtmosphereType::AtmosphericModelType: The type of atmospheric model used to compute the density. Available options are Jacchia-Bowman 2008 (JB2008), Jacchia-Roberts 1971 (JR1971), NRL MSIS 2000 (MSIS2000), Exponential (ExpAtmo), and None (None)

Returns

rho::Number: The density of the atmosphere at the provided time and point [kg/m^3].

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AstroForceModels.de_Sitter_acceleration — Method

de_Sitter_acceleration(
    u::AbstractArray,
    r_sun::AbstractArray,
    v_sun::AbstractArray,
    μ_Sun::Number;
    c::Number=SPEED_OF_LIGHT,
    γ::Number=1.0,
)

Computes the relativity acceleration acting on a spacecraft given a relativity model and current state and parameters of an object.

Arguments

u::AbstractArray: Current State of the simulation.
r_sun::AbstractArray: The position of the sun in the Earth inertial frame.
v_sun::AbstractArray: The velocity of the sun in the Earth inertial frame.
μ_Sun::Number: Gravitation Parameter of the Sun. [km^3/s^2]
c::Number: Speed of Light [km/s]
γ::Number: Post-Newtonian Parameterization parameter. γ=1 in General Relativity.

Returns

de_Sitter_acceleration: SVector{3}: The 3-dimensional de Sitter acceleration acting on the spacecraft.

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AstroForceModels.drag_accel — Method

drag_accel(u::AbstractArray, rho::Number, BC::Number, ω_vec::AbstractArray, t::Number, [DragModel]) -> SVector{3}{Number}

Compute the Acceleration Atmospheric Drag

The atmosphere is treated as a solid revolving with the Earth and the apparent velocity of the satellite is computed using the transport theorem

            𝐯_app = 𝐯 - 𝛚 x 𝐫

The acceleration from drag is then computed with a cannonball model as

            𝐚 = 1/2 * ρ * BC * |𝐯_app|₂^2 * v̂

Note

Currently only fixed cannonball state based ballistic coefficients are supported, custom models can be created for higher fidelity.

Arguments

u::AbstractArray: The current state of the spacecraft in the central body's inertial frame.
rho::Number: Atmospheric density at (t, u) [kg/m^3].
BC::Number: The ballistic coefficient of the satellite – (area/mass) * drag coefficient [kg/m^2].
ω_vec::AbstractArray: The angular velocity vector of Earth. Typically approximated as [0.0; 0.0; ω_Earth]
t::Number: Current time of the simulation.

Returns

SVector{3}{Number}: Inertial acceleration from drag

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AstroForceModels.get_position — Method

Computes the position of the celestial body using Vallado's ephemeris

Arguments

ephem_type::Symbol: Ephemeris type used to compute body's position.
body::CelestialBody: Celestial body acting on the craft.
time::Number: Current time of the simulation in seconds.

Returns

body_position: SVector{3}: The 3-dimensional third body position in the J2000 frame.

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AstroForceModels.get_velocity — Method

Computes the velocity of the celestial body using Vallado's ephemeris

Arguments

ephem_type::Symbol: Ephemeris type used to compute body's position.
body::CelestialBody: Celestial body acting on the craft.
time::Number: Current time of the simulation in seconds.

Returns

body_position: SVector{3}: The 3-dimensional third body position in the J2000 frame.

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AstroForceModels.lense_thirring_acceleration — Method

lense_thirring_acceleration(
    u::AbstractArray,
    μ_body::Number,
    J::AbstractArray;
    c::Number=SPEED_OF_LIGHT,
    γ::Number=1.0,
)

Computes the lense thirring relativity acceleration acting on a spacecraft given a relativity model and current state and parameters of an object.

Arguments

u::AbstractArray: Current State of the simulation.
μ_body::Number: Gravitation Parameter of the central body.
J::AbstractArray: Angular momentum vector per unit mass of the central body. [km^3/s^2]
c::Number: Speed of Light [km/s]
γ::Number: Post-Newtonian Parameterization parameter. γ=1 in General Relativity.

Returns

lense_thirring_acceleration: SVector{3}: The 3-dimensional lense thirring acceleration acting on the spacecraft.

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AstroForceModels.reflectivity_ballistic_coefficient — Method

reflectivityballisticcoefficient( u::AbstractArray, p::ComponentVector, t::Number, model::CannonballFixedSRP)

Returns the ballistic coefficient for a SRP model given the model and current state of the simulation.

Arguments

- `u::AbstractArray`: The current state of the simulation.
- `p::ComponentVector`: The parameters of the simulation.
- `t::Number`: The current time of the simulation.
- `model::CannonballFixedSRP`: SRP model for the spacecraft.

Returns

-`ballistic_coeff::Number`: The current ballistic coefficient of the spacecraft.

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AstroForceModels.reflectivity_ballistic_coefficient — Method

ballistic_coefficient( u::AbstractArray, p::ComponentVector, t::Number, model::StateSRPModel)

Returns the ballistic coefficient for a SRP model given the model and current state of the simulation.

Arguments

- `u::AbstractArray`: The current state of the simulation.
- `p::ComponentVector`: The parameters of the simulation.
- `t::Number`: The current time of the simulation.
- `model::StateSRPModel`: The SRP model for the spacecraft.

Returns

-`ballistic_coeff::Number`: The current ballistic coefficient of the spacecraft.

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AstroForceModels.relativity_accel — Method

relativity_accel(
    u::AbstractArray,
    r_sun::AbstractArray,
    v_sun::AbstractArray,
    μ_body::Number,
    μ_Sun::Number,
    J::AbstractArray;
    c::Number=SPEED_OF_LIGHT / 1E3,
    γ::Number=1.0,
    β::Number=1.0,
    schwartzchild_effect::Bool=true,
    lense_thirring_effect::Bool=true,
    de_Sitter_effect::Bool=true,
)

Computes the relativity acceleration acting on a spacecraft given a relativity model and current state and parameters of an object.

Arguments

u::AbstractArray: Current State of the simulation.
r_sun::AbstractArray: The position of the sun in the Earth inertial frame.
v_sun::AbstractArray: The velocity of the sun in the Earth inertial frame.
μ_body::Number: Gravitation Parameter of the central body.
μ_Sun::Number: Gravitation Parameter of the Sun. [km^3/s^2]
J::AbstractArray: Angular momentum vector per unit mass of the central body. [km^3/s^2]
c::Number: Speed of Light [km/s]
γ::Number: Post-Newtonian Parameterization parameter. γ=1 in General Relativity.
β::Number: Post-Newtonian Parameterization parameter. β=1 in General Relativity.
schwartzchild_effect::Bool: Include the Schwartzchild relativity effect.
lense_thirring_effect::Bool: Include the Lense Thirring relativity effect.
de_Sitter_effect::Bool: Include the De Sitter relativity effect.

Returns

acceleration: SVector{3}: The 3-dimensional relativity acceleration acting on the spacecraft.

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AstroForceModels.schwartzchild_acceleration — Method

schwartzchild_acceleration(
    u::AbstractArray, μ_body::Number; c::Number=SPEED_OF_LIGHT, γ::Number=1.0, β::Number=1.0
)

Computes the relativity acceleration acting on a spacecraft given a relativity model and current state and parameters of an object.

Arguments

u::AbstractArray: Current State of the simulation.
μ_body::Number: Gravitation Parameter of the central body.
c::Number: Speed of Light [km/s]
γ::Number: Post-Newtonian Parameterization parameter. γ=1 in General Relativity.
β::Number: Post-Newtonian Parameterization parameter. β=1 in General Relativity.

Returns

schwartzchild_acceleration: SVector{3}: The 3-dimensional schwartzchild acceleration acting on the spacecraft.

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AstroForceModels.shadow_model — Method

shadow_model(sat_pos::AbstractArray, sun_pos::AbstractArray, R_Sun::Number, R_Occulting::Number, t::Number, ShadowModel::ShadowModelType)

Computes the Lighting Factor of the Sun occur from the Umbra and Prenumbra of Earth's Shadow

Arguments

sat_pos::AbstractArray: The current satellite position.
sun_pos::AbstractArray: The current Sun position.
R_Sun::Number: The radius of the Sun.
R_Occulting::Number: The radius of the Occulting Body.
ShadowModel::ShadowModelType: The Earth shadow model to use. Current Options – Cylindrical, Conical, Conical_Simplified, None

Returns

SVector{3}{Number}: Inertial acceleration from the 3rd body

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AstroForceModels.srp_accel — Method

srp_accel(u::AbstractArray, sun_pos::AbstractArray, R_Sun::Number, R_Occulting::Number, Ψ::Number, RC::Number, t::Number; ShadowModel::ShadowModelType)

Compute the Acceleration from Solar Radiaiton Pressure

Radiation from the Sun reflects off the satellite's surface and transfers momentum perturbing the satellite's trajectory. This force can be computed using the a Cannonball model with the following equation

            𝐚 = F * RC * Ψ * (AU/(R_sc_Sun))^2 * R̂_sc_Sun

Note

Currently only Cannonball SRP is supported, to use a higher fidelity drag either use a state varying function or compute the ballistic coefficient further upstream

Arguments

u::AbstractArray: The current state of the spacecraft in the central body's inertial frame.
sun_pos::AbstractArray: The current position of the Sun.
R_Sun::Number: The radius of the Sun.
R_Occulting::Number: The radius of the Earth.
Ψ::Number: Solar Constant at 1 Astronomical Unit.
RC::Number: The solar ballistic coefficient of the satellite – (Area/mass) * Reflectivity Coefficient [kg/m^2].
t::Number: The current time of the Simulation

Optional Arguments

ShadowModel::ShadowModelType: SRP Earth Shadow Model to use. Current Options – :Conical, :Conical_Simplified, :Cylinderical

Returns

SVector{3}{Number}: Inertial acceleration from the 3rd body

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AstroForceModels.third_body_accel — Method

third_body_accel(u::AbstractArray, μ_body::Number, body_pos::AbstractArray, h::Number) -> SVector{3}{Number}

Compute the Acceleration from a 3rd Body Represented as a Point Mass

Since the central body is also being acted upon by the third body, the acceleration of body 𝐁 acting on spacecraft 𝐀 in the orbiting body's 𝐂 is part of the force not acting on the central body

            a = ∇UB(rA) - ∇UB(rC)

Arguments

u::AbstractArray: The current state of the spacecraft in the central body's inertial frame.
μ_body: Gravitation Parameter of the 3rd body.
body_pos::AbstractArray: The current position of the 3rd body in the central body's inertial frame.

Returns

SVector{3}{Number}: Inertial acceleration from the 3rd body

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