Package org.orekit.propagation.analytical.tle

Class FieldTLEPropagator<T extends CalculusFieldElement<T>>

java.lang.Object

org.orekit.propagation.FieldAbstractPropagator<T>

org.orekit.propagation.analytical.FieldAbstractAnalyticalPropagator<T>

org.orekit.propagation.analytical.tle.FieldTLEPropagator<T>

Type Parameters:

T - type of the field elements

All Implemented Interfaces:

FieldPropagator<T>, FieldPVCoordinatesProvider<T>, ParameterDriversProvider

Direct Known Subclasses:

FieldDeepSDP4, FieldSGP4

public abstract class FieldTLEPropagator<T extends CalculusFieldElement<T>>
extends FieldAbstractAnalyticalPropagator<T>

This class provides elements to propagate TLE's.

The models used are SGP4 and SDP4, initially proposed by NORAD as the unique convenient propagator for TLE's. Inputs and outputs of this propagator are only suited for NORAD two lines elements sets, since it uses estimations and mean values appropriate for TLE's only.

Deep- or near- space propagator is selected internally according to NORAD recommendations so that the user has not to worry about the used computation methods. One instance is created for each TLE (this instance can only be get using selectExtrapolator(FieldTLE, CalculusFieldElement[]) method, and can compute position and velocity coordinates at any time. Maximum accuracy is guaranteed in a 24h range period before and after the provided TLE epoch (of course this accuracy is not really measurable nor predictable: according to CelesTrak, the precision is close to one kilometer and error won't probably rise above 2 km).

This implementation is largely inspired from the paper and source code Revisiting Spacetrack Report #3 and is fully compliant with its results and tests cases.

Since:

11.0

Author:

Felix R. Hoots, Ronald L. Roehrich, December 1980 (original fortran), David A. Vallado, Paul Crawford, Richard Hujsak, T.S. Kelso (C++ translation and improvements), Fabien Maussion (java translation), Thomas Paulet (field translation)

See Also:

• FieldTLE

Field Summary

Fields

Modifier and Type	Field	Description
protected T	a	final semi major axis.
protected T	a0dp	original recovered semi major axis.
protected T	beta0	sqrt (1 - e2).
protected T	beta02	1 - e2.
protected T	c1	C1 from SPTRCK #3.
protected T	c2	C2 from SPTRCK #3.
protected T	c4	C4 from SPTRCK #3.
protected T	coef	coef for SGP C3 computation.
protected T	coef1	coef for SGP C5 computation.
protected T	cosi0	cosinus original inclination.
protected T	e	final eccentricity.
protected T	e0sq	original eccentricity squared.
protected T	eeta	original eccentricity * eta.
protected T	eta	eta from SPTRCK #3.
protected T	etasq	eta squared.
protected T	i	final inclination.
protected T	omega	final perigee argument.
protected T	omgdot	common parameter for perigee argument (omega) computation.
protected T	perige	perigee, expressed in KM and ALTITUDE.
protected T	s4	s* new value for the contant s.
protected T	sini0	sinus original inclination.
protected T	t2cof	3/2 * C1.
protected T	theta2	cos io squared.
protected FieldTLE<T>	tle	Initial state.
protected T	tsi	tsi from SPTRCK #3.
protected final TimeScale	utc	UTC time scale.
protected T	xl	L from SPTRCK #3.
protected T	xmdot	common parameter for mean anomaly (M) computation.
protected T	xn0dp	original recovered mean motion.
protected T	xnodcf	common parameter for raan (OMEGA) computation.
protected T	xnode	final RAAN.
protected T	xnodot	common parameter for raan (OMEGA) computation.

Fields inherited from interface org.orekit.propagation.FieldPropagator

DEFAULT_MASS

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	FieldTLEPropagator(FieldTLE<T> initialTLE, AttitudeProvider attitudeProvider, T mass, Frame teme, T[] parameters)	Protected constructor for derived classes.
protected	FieldTLEPropagator(FieldTLE<T> initialTLE, AttitudeProvider attitudeProvider, T mass, T[] parameters)	Protected constructor for derived classes.

Method Summary

Modifier and Type	Method	Description
Frame	getFrame()	Get the frame in which the orbit is propagated.
protected T	getMass(FieldAbsoluteDate<T> date)	Get the mass.
static double	getMU()	Get the Earth gravity coefficient used for TLE propagation.
List<ParameterDriver>	getParametersDrivers()	Get the drivers for parameters.
FieldPVCoordinates<T>	getPVCoordinates(FieldAbsoluteDate<T> date, T[] parameters)	Get the extrapolated position and velocity from an initial TLE.
FieldTLE<T>	getTLE()	Get the underlying TLE.
FieldOrbit<T>	propagateOrbit(FieldAbsoluteDate<T> date, T[] parameters)	Propagate an orbit up to a specific target date.
void	resetInitialState(FieldSpacecraftState<T> state)	Reset the propagator initial state.
protected void	resetIntermediateState(FieldSpacecraftState<T> state, boolean forward)	Reset an intermediate state.
static <T extends CalculusFieldElement<T>> FieldTLEPropagator<T>	selectExtrapolator(FieldTLE<T> tle, AttitudeProvider attitudeProvider, T mass, Frame teme, T[] parameters)	Selects the extrapolator to use with the selected TLE.
static <T extends CalculusFieldElement<T>> FieldTLEPropagator<T>	selectExtrapolator(FieldTLE<T> tle, AttitudeProvider attitudeProvider, T mass, T[] parameters)	Selects the extrapolator to use with the selected TLE.
static <T extends CalculusFieldElement<T>> FieldTLEPropagator<T>	selectExtrapolator(FieldTLE<T> tle, Frame teme, T[] parameters)	Selects the extrapolator to use with the selected TLE.
static <T extends CalculusFieldElement<T>> FieldTLEPropagator<T>	selectExtrapolator(FieldTLE<T> tle, T[] parameters)	Selects the extrapolator to use with the selected TLE.
protected abstract void	sxpInitialize(T[] parameters)	Initialization proper to each propagator (SGP or SDP).
protected abstract void	sxpPropagate(T t, T[] parameters)	Propagation proper to each propagator (SGP or SDP).

Methods inherited from class org.orekit.propagation.analytical.FieldAbstractAnalyticalPropagator

acceptStep, addEventDetector, basicPropagate, clearEventsDetectors, getEphemerisGenerator, getEventDetectors, propagate

Methods inherited from class org.orekit.propagation.FieldAbstractPropagator

addAdditionalDataProvider, getAdditionalDataProviders, getAttitudeProvider, getField, getInitialState, getManagedAdditionalData, getMultiplexer, getStartDate, initializeAdditionalData, initializePropagation, isAdditionalDataManaged, propagate, removeAdditionalDataProvider, setAttitudeProvider, setStartDate, stateChanged, updateAdditionalData, updateUnmanagedData

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.FieldPropagator

clearStepHandlers, getPosition, getPVCoordinates, getVelocity, setStepHandler, setStepHandler

Methods inherited from interface org.orekit.utils.ParameterDriversProvider

getNbParametersDriversValue, getParameterDriver, getParameters, getParameters, getParameters, getParameters, getParametersAllValues, getParametersAllValues, isSupported

Field Details

tle

protected FieldTLE<T extends CalculusFieldElement<T>> tle

Initial state.

utc

protected final TimeScale utc

UTC time scale.

xnode

protected T extends CalculusFieldElement<T> xnode

final RAAN.

a

protected T extends CalculusFieldElement<T> a

final semi major axis.

e

protected T extends CalculusFieldElement<T> e

final eccentricity.

i

protected T extends CalculusFieldElement<T> i

final inclination.

omega

protected T extends CalculusFieldElement<T> omega

final perigee argument.

xl

protected T extends CalculusFieldElement<T> xl

L from SPTRCK #3.

a0dp

protected T extends CalculusFieldElement<T> a0dp

original recovered semi major axis.

xn0dp

protected T extends CalculusFieldElement<T> xn0dp

original recovered mean motion.

cosi0

protected T extends CalculusFieldElement<T> cosi0

cosinus original inclination.

theta2

protected T extends CalculusFieldElement<T> theta2

cos io squared.

sini0

protected T extends CalculusFieldElement<T> sini0

sinus original inclination.

xmdot

protected T extends CalculusFieldElement<T> xmdot

common parameter for mean anomaly (M) computation.

omgdot

protected T extends CalculusFieldElement<T> omgdot

common parameter for perigee argument (omega) computation.

xnodot

protected T extends CalculusFieldElement<T> xnodot

common parameter for raan (OMEGA) computation.

e0sq

protected T extends CalculusFieldElement<T> e0sq

original eccentricity squared.

beta02

protected T extends CalculusFieldElement<T> beta02

1 - e2.

beta0

protected T extends CalculusFieldElement<T> beta0

sqrt (1 - e2).

perige

protected T extends CalculusFieldElement<T> perige

perigee, expressed in KM and ALTITUDE.

etasq

protected T extends CalculusFieldElement<T> etasq

eta squared.

eeta

protected T extends CalculusFieldElement<T> eeta

original eccentricity * eta.

s4

protected T extends CalculusFieldElement<T> s4

s* new value for the contant s.

tsi

protected T extends CalculusFieldElement<T> tsi

tsi from SPTRCK #3.

eta

protected T extends CalculusFieldElement<T> eta

eta from SPTRCK #3.

coef

protected T extends CalculusFieldElement<T> coef

coef for SGP C3 computation.

coef1

protected T extends CalculusFieldElement<T> coef1

coef for SGP C5 computation.

c1

protected T extends CalculusFieldElement<T> c1

C1 from SPTRCK #3.

c2

protected T extends CalculusFieldElement<T> c2

C2 from SPTRCK #3.

c4

protected T extends CalculusFieldElement<T> c4

C4 from SPTRCK #3.

xnodcf

protected T extends CalculusFieldElement<T> xnodcf

common parameter for raan (OMEGA) computation.

t2cof

protected T extends CalculusFieldElement<T> t2cof

3/2 * C1.

Constructor Details

FieldTLEPropagator

@DefaultDataContext
protected FieldTLEPropagator(FieldTLE<T> initialTLE,
 AttitudeProvider attitudeProvider,
 T mass,
 T[] parameters)

Protected constructor for derived classes.

This constructor uses the default data context.

Parameters:

initialTLE - the unique TLE to propagate

attitudeProvider - provider for attitude computation

mass - spacecraft mass (kg)

parameters - SGP4 and SDP4 model parameters

See Also:

• FieldTLEPropagator(FieldTLE, AttitudeProvider, CalculusFieldElement, Frame, CalculusFieldElement[])

FieldTLEPropagator

protected FieldTLEPropagator(FieldTLE<T> initialTLE,
 AttitudeProvider attitudeProvider,
 T mass,
 Frame teme,
 T[] parameters)

Protected constructor for derived classes.

Parameters:

initialTLE - the unique TLE to propagate

attitudeProvider - provider for attitude computation

mass - spacecraft mass (kg)

teme - the TEME frame to use for propagation.

parameters - SGP4 and SDP4 model parameters

Method Details

selectExtrapolator

@DefaultDataContext
public static <T extends CalculusFieldElement<T>>
FieldTLEPropagator<T> selectExtrapolator(FieldTLE<T> tle,
 T[] parameters)

Selects the extrapolator to use with the selected TLE.

This method uses the default data context.

Type Parameters:

T - elements type

Parameters:

tle - the TLE to propagate.

parameters - SGP4 and SDP4 model parameters

Returns:

the correct propagator.

See Also:

• selectExtrapolator(FieldTLE, Frame, CalculusFieldElement[])

selectExtrapolator

public static <T extends CalculusFieldElement<T>>
FieldTLEPropagator<T> selectExtrapolator(FieldTLE<T> tle,
 Frame teme,
 T[] parameters)

Selects the extrapolator to use with the selected TLE.

This method uses the default data context.

Type Parameters:

T - elements type

Parameters:

tle - the TLE to propagate.

teme - TEME frame.

parameters - SGP4 and SDP4 model parameters

Returns:

the correct propagator.

selectExtrapolator

@DefaultDataContext
public static <T extends CalculusFieldElement<T>>
FieldTLEPropagator<T> selectExtrapolator(FieldTLE<T> tle,
 AttitudeProvider attitudeProvider,
 T mass,
 T[] parameters)

Selects the extrapolator to use with the selected TLE.

This method uses the default data context.

Type Parameters:

T - elements type

Parameters:

tle - the TLE to propagate.

attitudeProvider - provider for attitude computation

mass - spacecraft mass (kg)

parameters - SGP4 and SDP4 model parameters

Returns:

the correct propagator.

See Also:

• selectExtrapolator(FieldTLE, AttitudeProvider, CalculusFieldElement, Frame, CalculusFieldElement[])

selectExtrapolator

public static <T extends CalculusFieldElement<T>>
FieldTLEPropagator<T> selectExtrapolator(FieldTLE<T> tle,
 AttitudeProvider attitudeProvider,
 T mass,
 Frame teme,
 T[] parameters)

Selects the extrapolator to use with the selected TLE.

Type Parameters:

T - elements type

Parameters:

tle - the TLE to propagate.

attitudeProvider - provider for attitude computation

mass - spacecraft mass (kg)

teme - the TEME frame to use for propagation.

parameters - SGP4 and SDP4 model parameters

Returns:

the correct propagator.

getMU

public static double getMU()

Get the Earth gravity coefficient used for TLE propagation.

Returns:

the Earth gravity coefficient.

getPVCoordinates

public FieldPVCoordinates<T> getPVCoordinates(FieldAbsoluteDate<T> date,
 T[] parameters)

Get the extrapolated position and velocity from an initial TLE.

Parameters:

date - the final date

parameters - values of the model

Returns:

the final PVCoordinates

getParametersDrivers

public List<ParameterDriver> getParametersDrivers()

Get the drivers for parameters.

Returns:

drivers for parameters

sxpInitialize

protected abstract void sxpInitialize(T[] parameters)

Initialization proper to each propagator (SGP or SDP).

Parameters:

parameters - model parameters

sxpPropagate

protected abstract void sxpPropagate(T t,
 T[] parameters)

Propagation proper to each propagator (SGP or SDP).

Parameters:

t - the offset from initial epoch (min)

parameters - model parameters

resetInitialState

public void resetInitialState(FieldSpacecraftState<T> state)

Reset the propagator initial state.

For TLE propagator, calling this method is only recommended for covariance propagation when the new state differs from the previous one by only adding the additional state containing the derivatives.

Specified by:

resetInitialState in interface FieldPropagator<T extends CalculusFieldElement<T>>

Overrides:

resetInitialState in class FieldAbstractPropagator<T extends CalculusFieldElement<T>>

Parameters:

state - new initial state to consider

resetIntermediateState

protected void resetIntermediateState(FieldSpacecraftState<T> state,
 boolean forward)

Reset an intermediate state.

Specified by:

resetIntermediateState in class FieldAbstractAnalyticalPropagator<T extends CalculusFieldElement<T>>

Parameters:

state - new intermediate state to consider

forward - if true, the intermediate state is valid for propagations after itself

getMass

protected T getMass(FieldAbsoluteDate<T> date)

Get the mass.

Specified by:

getMass in class FieldAbstractAnalyticalPropagator<T extends CalculusFieldElement<T>>

Parameters:

date - target date for the orbit

Returns:

mass mass

propagateOrbit

public FieldOrbit<T> propagateOrbit(FieldAbsoluteDate<T> date,
 T[] parameters)

Propagate an orbit up to a specific target date.

Specified by:

propagateOrbit in class FieldAbstractAnalyticalPropagator<T extends CalculusFieldElement<T>>

Parameters:

date - target date for the orbit

parameters - model parameters

Returns:

propagated orbit

getTLE

public FieldTLE<T> getTLE()

Get the underlying TLE. If there has been calls to #resetInitialState or #resetIntermediateState, it will not be the same as given to the constructor.

Returns:

underlying TLE

getFrame

public Frame getFrame()

Get the frame in which the orbit is propagated.

The propagation frame is the definition frame of the initial state, so this method should be called after this state has been set, otherwise it may return null.

Specified by:

getFrame in interface FieldPropagator<T extends CalculusFieldElement<T>>

Overrides:

getFrame in class FieldAbstractPropagator<T extends CalculusFieldElement<T>>

Returns:

frame in which the orbit is propagated

See Also:

• FieldPropagator.resetInitialState(FieldSpacecraftState)