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org.orekit.propagation.analytical

Class EcksteinHechlerPropagator

• All Implemented Interfaces:
Propagator, PVCoordinatesProvider

public class EcksteinHechlerPropagator
extends AbstractAnalyticalPropagator
This class propagates a SpacecraftState using the analytical Eckstein-Hechler model.

The Eckstein-Hechler model is suited for near circular orbits (e < 0.1, with poor accuracy between 0.005 and 0.1) and inclination neither equatorial (direct or retrograde) nor critical (direct or retrograde).

Note that before version 7.0, there was a large inconsistency in the generated orbits, and it was fixed as of version 7.0 of Orekit, with a visible side effect. The problems is that if the circular parameters produced by the Eckstein-Hechler model are used to build an orbit considered to be osculating, the velocity deduced from this orbit was inconsistent with the position evolution! The reason is that the model includes non-Keplerian effects but it does not include a corresponding circular/Cartesian conversion. As a consequence, all subsequent computation involving velocity were wrong. This includes attitude modes like yaw compensation and Doppler effect. As this effect was considered serious enough and as accurate velocities were considered important, the propagator now generates Cartesian orbits which are built in a special way to ensure consistency throughout propagation. A side effect is that if circular parameters are rebuilt by user from these propagated Cartesian orbit, the circular parameters will generally not match the initial orbit (differences in semi-major axis can exceed 120 m). The position however will match to sub-micrometer level, and this position will be identical to the positions that were generated by previous versions (in other words, the internals of the models have not been changed, only the output parameters have been changed). The correctness of the initialization has been assessed and is good, as it allows the subsequent orbit to remain close to a numerical reference orbit.

If users need a more definitive initialization of an Eckstein-Hechler propagator, they should consider using a propagator converter to initialize their Eckstein-Hechler propagator using a complete sample instead of just a single initial orbit.

Author:
Guylaine Prat
See Also:
Orbit

• Fields inherited from interface org.orekit.propagation.Propagator

DEFAULT_LAW, DEFAULT_MASS, EPHEMERIS_GENERATION_MODE, MASTER_MODE, SLAVE_MODE
• Constructor Summary

Constructors
Constructor and Description
EcksteinHechlerPropagator(Orbit initialOrbit, AttitudeProvider attitudeProv, double referenceRadius, double mu, double c20, double c30, double c40, double c50, double c60)
Build a propagator from orbit, attitude provider and potential.
EcksteinHechlerPropagator(Orbit initialOrbit, AttitudeProvider attitudeProv, double mass, double referenceRadius, double mu, double c20, double c30, double c40, double c50, double c60)
Build a propagator from orbit, attitude provider, mass and potential.
EcksteinHechlerPropagator(Orbit initialOrbit, AttitudeProvider attitudeProv, double mass, double referenceRadius, double mu, double c20, double c30, double c40, double c50, double c60, PropagationType initialType)
Build a propagator from orbit, attitude provider, mass and potential.
EcksteinHechlerPropagator(Orbit initialOrbit, AttitudeProvider attitudeProv, double mass, UnnormalizedSphericalHarmonicsProvider provider)
Build a propagator from orbit, attitude provider, mass and potential provider.
EcksteinHechlerPropagator(Orbit initialOrbit, AttitudeProvider attitudeProv, double mass, UnnormalizedSphericalHarmonicsProvider provider, PropagationType initialType)
Build a propagator from orbit, attitude provider, mass and potential provider.
EcksteinHechlerPropagator(Orbit initialOrbit, AttitudeProvider attitude, double mass, UnnormalizedSphericalHarmonicsProvider provider, UnnormalizedSphericalHarmonicsProvider.UnnormalizedSphericalHarmonics harmonics)
Private helper constructor.
EcksteinHechlerPropagator(Orbit initialOrbit, AttitudeProvider attitude, double mass, UnnormalizedSphericalHarmonicsProvider provider, UnnormalizedSphericalHarmonicsProvider.UnnormalizedSphericalHarmonics harmonics, PropagationType initialType)
Private helper constructor.
EcksteinHechlerPropagator(Orbit initialOrbit, AttitudeProvider attitudeProv, UnnormalizedSphericalHarmonicsProvider provider)
Build a propagator from orbit, attitude provider and potential provider.
EcksteinHechlerPropagator(Orbit initialOrbit, double referenceRadius, double mu, double c20, double c30, double c40, double c50, double c60)
Build a propagator from orbit and potential.
EcksteinHechlerPropagator(Orbit initialOrbit, double mass, double referenceRadius, double mu, double c20, double c30, double c40, double c50, double c60)
Build a propagator from orbit, mass and potential.
EcksteinHechlerPropagator(Orbit initialOrbit, double mass, UnnormalizedSphericalHarmonicsProvider provider)
Build a propagator from orbit, mass and potential provider.
EcksteinHechlerPropagator(Orbit initialOrbit, UnnormalizedSphericalHarmonicsProvider provider)
Build a propagator from orbit and potential provider.
EcksteinHechlerPropagator(Orbit initialOrbit, UnnormalizedSphericalHarmonicsProvider provider, PropagationType initialType)
Build a propagator from orbit and potential provider.
• Method Summary

All Methods
Modifier and Type Method and Description
protected double getMass(AbsoluteDate date)
Get the mass.
CartesianOrbit propagateOrbit(AbsoluteDate date)
Extrapolate an orbit up to a specific target date.
void resetInitialState(SpacecraftState state)
Reset the propagator initial state.
void resetInitialState(SpacecraftState state, PropagationType stateType)
Reset the propagator initial state.
protected void resetIntermediateState(SpacecraftState state, boolean forward)
Reset an intermediate state.
• Methods inherited from class org.orekit.propagation.analytical.AbstractAnalyticalPropagator

acceptStep, addEventDetector, basicPropagate, clearEventsDetectors, getEventsDetectors, getGeneratedEphemeris, getPvProvider, propagate
• Methods inherited from class org.orekit.propagation.AbstractPropagator

addAdditionalStateProvider, getAdditionalStateProviders, getAttitudeProvider, getFixedStepSize, getFrame, getInitialState, getManagedAdditionalStates, getMode, getPVCoordinates, getStartDate, getStepHandler, initializePropagation, isAdditionalStateManaged, propagate, setAttitudeProvider, setEphemerisMode, setEphemerisMode, setMasterMode, setMasterMode, setSlaveMode, setStartDate, stateChanged, updateAdditionalStates
• Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
• Methods inherited from interface org.orekit.propagation.Propagator

getDefaultLaw
• Constructor Detail

• EcksteinHechlerPropagator

@DefaultDataContext
public EcksteinHechlerPropagator(Orbit initialOrbit,
double referenceRadius,
double mu,
double c20,
double c30,
double c40,
double c50,
double c60)
Build a propagator from orbit and potential.

Mass and attitude provider are set to unspecified non-null arbitrary values.

The Cn,0 coefficients are the denormalized zonal coefficients, they are related to both the normalized coefficients Cn,0 and the Jn one as follows:

Cn,0 = [(2-δ0,m)(2n+1)(n-m)!/(n+m)!]½ Cn,0

Cn,0 = -Jn

This constructor uses the default data context.

Using this constructor, an initial osculating orbit is considered.

Parameters:
initialOrbit - initial orbit
referenceRadius - reference radius of the Earth for the potential model (m)
mu - central attraction coefficient (m³/s²)
c20 - un-normalized zonal coefficient (about -1.08e-3 for Earth)
c30 - un-normalized zonal coefficient (about +2.53e-6 for Earth)
c40 - un-normalized zonal coefficient (about +1.62e-6 for Earth)
c50 - un-normalized zonal coefficient (about +2.28e-7 for Earth)
c60 - un-normalized zonal coefficient (about -5.41e-7 for Earth)
See Also:
Constants, EcksteinHechlerPropagator(Orbit, AttitudeProvider, double, double, double, double, double, double, double, double)
• EcksteinHechlerPropagator

@DefaultDataContext
public EcksteinHechlerPropagator(Orbit initialOrbit,
double mass,
double referenceRadius,
double mu,
double c20,
double c30,
double c40,
double c50,
double c60)
Build a propagator from orbit, mass and potential.

Attitude law is set to an unspecified non-null arbitrary value.

The Cn,0 coefficients are the denormalized zonal coefficients, they are related to both the normalized coefficients Cn,0 and the Jn one as follows:

Cn,0 = [(2-δ0,m)(2n+1)(n-m)!/(n+m)!]½ Cn,0

Cn,0 = -Jn

This constructor uses the default data context.

Using this constructor, an initial osculating orbit is considered.

Parameters:
initialOrbit - initial orbit
mass - spacecraft mass
referenceRadius - reference radius of the Earth for the potential model (m)
mu - central attraction coefficient (m³/s²)
c20 - un-normalized zonal coefficient (about -1.08e-3 for Earth)
c30 - un-normalized zonal coefficient (about +2.53e-6 for Earth)
c40 - un-normalized zonal coefficient (about +1.62e-6 for Earth)
c50 - un-normalized zonal coefficient (about +2.28e-7 for Earth)
c60 - un-normalized zonal coefficient (about -5.41e-7 for Earth)
See Also:
EcksteinHechlerPropagator(Orbit, AttitudeProvider, double, double, double, double, double, double, double, double)
• EcksteinHechlerPropagator

public EcksteinHechlerPropagator(Orbit initialOrbit,
AttitudeProvider attitudeProv,
UnnormalizedSphericalHarmonicsProvider provider)
Build a propagator from orbit, attitude provider and potential provider.

Mass is set to an unspecified non-null arbitrary value.

Using this constructor, an initial osculating orbit is considered.

Parameters:
initialOrbit - initial orbit
attitudeProv - attitude provider
provider - for un-normalized zonal coefficients
• EcksteinHechlerPropagator

public EcksteinHechlerPropagator(Orbit initialOrbit,
AttitudeProvider attitudeProv,
double referenceRadius,
double mu,
double c20,
double c30,
double c40,
double c50,
double c60)
Build a propagator from orbit, attitude provider and potential.

Mass is set to an unspecified non-null arbitrary value.

The Cn,0 coefficients are the denormalized zonal coefficients, they are related to both the normalized coefficients Cn,0 and the Jn one as follows:

Cn,0 = [(2-δ0,m)(2n+1)(n-m)!/(n+m)!]½ Cn,0

Cn,0 = -Jn

Using this constructor, an initial osculating orbit is considered.

Parameters:
initialOrbit - initial orbit
attitudeProv - attitude provider
referenceRadius - reference radius of the Earth for the potential model (m)
mu - central attraction coefficient (m³/s²)
c20 - un-normalized zonal coefficient (about -1.08e-3 for Earth)
c30 - un-normalized zonal coefficient (about +2.53e-6 for Earth)
c40 - un-normalized zonal coefficient (about +1.62e-6 for Earth)
c50 - un-normalized zonal coefficient (about +2.28e-7 for Earth)
c60 - un-normalized zonal coefficient (about -5.41e-7 for Earth)
• EcksteinHechlerPropagator

public EcksteinHechlerPropagator(Orbit initialOrbit,
AttitudeProvider attitudeProv,
double mass,
UnnormalizedSphericalHarmonicsProvider provider)
Build a propagator from orbit, attitude provider, mass and potential provider.

Using this constructor, an initial osculating orbit is considered.

Parameters:
initialOrbit - initial orbit
attitudeProv - attitude provider
mass - spacecraft mass
provider - for un-normalized zonal coefficients
See Also:
EcksteinHechlerPropagator(Orbit, AttitudeProvider, double, UnnormalizedSphericalHarmonicsProvider, PropagationType)
• EcksteinHechlerPropagator

public EcksteinHechlerPropagator(Orbit initialOrbit,
AttitudeProvider attitudeProv,
double mass,
double referenceRadius,
double mu,
double c20,
double c30,
double c40,
double c50,
double c60)
Build a propagator from orbit, attitude provider, mass and potential.

The Cn,0 coefficients are the denormalized zonal coefficients, they are related to both the normalized coefficients Cn,0 and the Jn one as follows:

Cn,0 = [(2-δ0,m)(2n+1)(n-m)!/(n+m)!]½ Cn,0

Cn,0 = -Jn

Using this constructor, an initial osculating orbit is considered.

Parameters:
initialOrbit - initial orbit
attitudeProv - attitude provider
mass - spacecraft mass
referenceRadius - reference radius of the Earth for the potential model (m)
mu - central attraction coefficient (m³/s²)
c20 - un-normalized zonal coefficient (about -1.08e-3 for Earth)
c30 - un-normalized zonal coefficient (about +2.53e-6 for Earth)
c40 - un-normalized zonal coefficient (about +1.62e-6 for Earth)
c50 - un-normalized zonal coefficient (about +2.28e-7 for Earth)
c60 - un-normalized zonal coefficient (about -5.41e-7 for Earth)
See Also:
EcksteinHechlerPropagator(Orbit, AttitudeProvider, double, double, double, double, double, double, double, double, PropagationType)
• EcksteinHechlerPropagator

@DefaultDataContext
public EcksteinHechlerPropagator(Orbit initialOrbit,
UnnormalizedSphericalHarmonicsProvider provider,
PropagationType initialType)
Build a propagator from orbit and potential provider.

Mass and attitude provider are set to unspecified non-null arbitrary values.

This constructor uses the default data context.

Using this constructor, it is possible to define the initial orbit as a mean Eckstein-Hechler orbit or an osculating one.

Parameters:
initialOrbit - initial orbit
provider - for un-normalized zonal coefficients
initialType - initial orbit type (mean Eckstein-Hechler orbit or osculating orbit)
Since:
10.2
• EcksteinHechlerPropagator

public EcksteinHechlerPropagator(Orbit initialOrbit,
AttitudeProvider attitudeProv,
double mass,
UnnormalizedSphericalHarmonicsProvider provider,
PropagationType initialType)
Build a propagator from orbit, attitude provider, mass and potential provider.

Using this constructor, it is possible to define the initial orbit as a mean Eckstein-Hechler orbit or an osculating one.

Parameters:
initialOrbit - initial orbit
attitudeProv - attitude provider
mass - spacecraft mass
provider - for un-normalized zonal coefficients
initialType - initial orbit type (mean Eckstein-Hechler orbit or osculating orbit)
Since:
10.2
• EcksteinHechlerPropagator

public EcksteinHechlerPropagator(Orbit initialOrbit,
AttitudeProvider attitude,
double mass,
UnnormalizedSphericalHarmonicsProvider provider,
UnnormalizedSphericalHarmonicsProvider.UnnormalizedSphericalHarmonics harmonics,
PropagationType initialType)
Private helper constructor.

Using this constructor, it is possible to define the initial orbit as a mean Eckstein-Hechler orbit or an osculating one.

Parameters:
initialOrbit - initial orbit
attitude - attitude provider
mass - spacecraft mass
provider - for un-normalized zonal coefficients
harmonics - provider.onDate(initialOrbit.getDate())
initialType - initial orbit type (mean Eckstein-Hechler orbit or osculating orbit)
Since:
10.2
• EcksteinHechlerPropagator

public EcksteinHechlerPropagator(Orbit initialOrbit,
AttitudeProvider attitudeProv,
double mass,
double referenceRadius,
double mu,
double c20,
double c30,
double c40,
double c50,
double c60,
PropagationType initialType)
Build a propagator from orbit, attitude provider, mass and potential.

The Cn,0 coefficients are the denormalized zonal coefficients, they are related to both the normalized coefficients Cn,0 and the Jn one as follows:

Cn,0 = [(2-δ0,m)(2n+1)(n-m)!/(n+m)!]½ Cn,0

Cn,0 = -Jn

Using this constructor, it is possible to define the initial orbit as a mean Eckstein-Hechler orbit or an osculating one.

Parameters:
initialOrbit - initial orbit
attitudeProv - attitude provider
mass - spacecraft mass
referenceRadius - reference radius of the Earth for the potential model (m)
mu - central attraction coefficient (m³/s²)
c20 - un-normalized zonal coefficient (about -1.08e-3 for Earth)
c30 - un-normalized zonal coefficient (about +2.53e-6 for Earth)
c40 - un-normalized zonal coefficient (about +1.62e-6 for Earth)
c50 - un-normalized zonal coefficient (about +2.28e-7 for Earth)
c60 - un-normalized zonal coefficient (about -5.41e-7 for Earth)
initialType - initial orbit type (mean Eckstein-Hechler orbit or osculating orbit)
Since:
10.2
• Method Detail

• resetInitialState

public void resetInitialState(SpacecraftState state)
Reset the propagator initial state.

The new initial state to consider must be defined with an osculating orbit.

Specified by:
resetInitialState in interface Propagator
Overrides:
resetInitialState in class AbstractPropagator
Parameters:
state - new initial state to consider
See Also:
resetInitialState(SpacecraftState, PropagationType)
• resetInitialState

public void resetInitialState(SpacecraftState state,
PropagationType stateType)
Reset the propagator initial state.
Parameters:
state - new initial state to consider
stateType - mean Eckstein-Hechler orbit or osculating orbit
Since:
10.2
• resetIntermediateState

protected void resetIntermediateState(SpacecraftState state,
boolean forward)
Reset an intermediate state.
Specified by:
resetIntermediateState in class AbstractAnalyticalPropagator
Parameters:
state - new intermediate state to consider
forward - if true, the intermediate state is valid for propagations after itself
• propagateOrbit

public CartesianOrbit propagateOrbit(AbsoluteDate date)
Extrapolate an orbit up to a specific target date.
Specified by:
propagateOrbit in class AbstractAnalyticalPropagator
Parameters:
date - target date for the orbit
Returns:
extrapolated parameters
• getMass

protected double getMass(AbsoluteDate date)
Get the mass.
Specified by:
getMass in class AbstractAnalyticalPropagator
Parameters:
date - target date for the orbit
Returns:
mass mass
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