Package org.orekit.estimation.measurements

Class FDOA

java.lang.Object

org.orekit.estimation.measurements.AbstractMeasurement<T>

org.orekit.estimation.measurements.SignalBasedMeasurement<T>

org.orekit.estimation.measurements.FDOA

All Implemented Interfaces:

Comparable<ComparableMeasurement>, ComparableMeasurement, ObservedMeasurement<FDOA>, TimeStamped, ParameterDriversProvider

public class FDOA
extends SignalBasedMeasurement<T>

Class modeling a Frequency Difference of Arrival measurement with a satellite as emitter and two ground stations as receivers.

FDOA measures the difference in signal arrival frequency between the emitter and receivers, corresponding to a difference in range-rate from the two receivers to the emitter.

The date of the measurement corresponds to the reception of the signal by the prime station. The measurement corresponds to the frequency of the signal received at the prime station at the date of the measurement minus the frequency of the signal received at the second station: fdoa = f1 - f2

The motion of the stations and the satellite during the signal flight time are taken into account.

Since:

12.0

Author:

Mark Rutten

Field Summary

Fields

Modifier and Type	Field	Description
static String	MEASUREMENT_TYPE	Type of the measurement.

Constructor Summary

Constructors

Constructor	Description
FDOA(Observer primeObserver, Observer secondObserver, double centreFrequency, AbsoluteDate date, double fdoa, double sigma, double baseWeight, ObservableSatellite satellite)	Constructor with default signal travel time model.
FDOA(Observer primeObserver, Observer secondObserver, double centreFrequency, AbsoluteDate date, double fdoa, double sigma, double baseWeight, SignalTravelTimeModel signalTravelTimeModel, ObservableSatellite satellite)	Constructor.

Method Summary

Modifier and Type	Method	Description
protected Gradient[]	computeDelays(SpacecraftState[] states)	Compute signal delays (always positive).
protected void	fillEstimation(Gradient quantity, Map<String,Integer> paramIndices, EstimatedMeasurement<T> estimated)	Fill estimated measurements with value and derivatives.
double	getCentreFrequency()	Get centre frequency of carrier wave.
Observer	getPrimeObserver()	Get the prime observer, the one that receives the signal first.
GroundStation	getPrimeStation()	Deprecated. as of 14.0, replaced by getPrimeObserver()
Observer	getSecondObserver()	Get the second observer, the one that gives the measurement.
GroundStation	getSecondStation()	Deprecated. as of 14.0, replaced by getSecondObserver()
protected EstimatedMeasurement<FDOA>	theoreticalEvaluation(int iteration, int evaluation, SpacecraftState[] states)	Estimate the theoretical value.
protected EstimatedMeasurementBase<FDOA>	theoreticalEvaluationWithoutDerivatives(int iteration, int evaluation, SpacecraftState[] states)	Estimate the theoretical value without derivatives.

Methods inherited from class org.orekit.estimation.measurements.SignalBasedMeasurement

getSignalTravelTimeModel, isTwoWay

Methods inherited from class org.orekit.estimation.measurements.AbstractMeasurement

addModifier, addParameterDriver, addParametersDrivers, estimate, estimateWithoutDerivatives, getBaseWeight, getCoordinates, getDate, getDimension, getMeasurementQuality, getModifiers, getObservedValue, getParameterIndices, getParametersDrivers, getSatellites, getTheoreticalStandardDeviation, isEnabled, setEnabled, setObservedValue

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.orekit.estimation.measurements.ComparableMeasurement

compareTo

Methods inherited from interface org.orekit.estimation.measurements.ObservedMeasurement

estimateWithoutDerivatives, getMeasurementType

Methods inherited from interface org.orekit.utils.ParameterDriversProvider

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

Methods inherited from interface org.orekit.time.TimeStamped

durationFrom

Field Detail

MEASUREMENT_TYPE

public static final String MEASUREMENT_TYPE

Type of the measurement.

See Also:

Constant Field Values

Constructor Detail

FDOA

public FDOA(Observer primeObserver,
            Observer secondObserver,
            double centreFrequency,
            AbsoluteDate date,
            double fdoa,
            double sigma,
            double baseWeight,
            ObservableSatellite satellite)

Constructor with default signal travel time model.

Parameters:

primeObserver - observer that gives the date of the measurement

secondObserver - observer that gives the measurement

centreFrequency - satellite emitter frequency (Hz)

date - date of the measurement

fdoa - observed value (Hz)

sigma - theoretical standard deviation

baseWeight - base weight

satellite - satellite related to this measurement

FDOA

public FDOA(Observer primeObserver,
            Observer secondObserver,
            double centreFrequency,
            AbsoluteDate date,
            double fdoa,
            double sigma,
            double baseWeight,
            SignalTravelTimeModel signalTravelTimeModel,
            ObservableSatellite satellite)

Constructor.

Parameters:

primeObserver - observer that gives the date of the measurement

secondObserver - observer that gives the measurement

centreFrequency - satellite emitter frequency (Hz)

date - date of the measurement

fdoa - observed value (Hz)

sigma - theoretical standard deviation

baseWeight - base weight

signalTravelTimeModel - signal travel time model

satellite - satellite related to this measurement

Since:

14.0

Method Detail

getCentreFrequency

public double getCentreFrequency()

Get centre frequency of carrier wave.

Returns:

frequency value (Hz)

theoreticalEvaluationWithoutDerivatives

protected EstimatedMeasurementBase<FDOA> theoreticalEvaluationWithoutDerivatives(int iteration,
                                                                                 int evaluation,
                                                                                 SpacecraftState[] states)

Estimate the theoretical value without derivatives. The default implementation uses the computation with derivatives and ought to be overwritten for performance.

The theoretical value does not have any modifiers applied.

Overrides:

theoreticalEvaluationWithoutDerivatives in class AbstractMeasurement<FDOA>

Parameters:

iteration - iteration number

evaluation - evaluation number

states - orbital states at measurement date

Returns:

theoretical value

See Also:

AbstractMeasurement.estimate(int, int, SpacecraftState[])

theoreticalEvaluation

protected EstimatedMeasurement<FDOA> theoreticalEvaluation(int iteration,
                                                           int evaluation,
                                                           SpacecraftState[] states)

Estimate the theoretical value.

The theoretical value does not have any modifiers applied.

Specified by:

theoreticalEvaluation in class AbstractMeasurement<FDOA>

Parameters:

iteration - iteration number

evaluation - evaluation number

states - orbital states at measurement date

Returns:

theoretical value

See Also:

AbstractMeasurement.estimate(int, int, SpacecraftState[])

getPrimeStation

@Deprecated
public GroundStation getPrimeStation()

Deprecated.

as of 14.0, replaced by getPrimeObserver()

Get the prime ground station, the one that receives the signal first.

Returns:

prime ground station

getPrimeObserver

public Observer getPrimeObserver()

Get the prime observer, the one that receives the signal first.

Returns:

prime observer

getSecondStation

@Deprecated
public GroundStation getSecondStation()

Deprecated.

as of 14.0, replaced by getSecondObserver()

Get the second ground station, the one that receives the signal first.

Returns:

second ground station

getSecondObserver

public Observer getSecondObserver()

Get the second observer, the one that gives the measurement.

Returns:

second observer

computeDelays

protected Gradient[] computeDelays(SpacecraftState[] states)

Compute signal delays (always positive).

Parameters:

states - observed states

Returns:

delays (to prime and second sensors)

fillEstimation

protected void fillEstimation(Gradient quantity,
                              Map<String,Integer> paramIndices,
                              EstimatedMeasurement<T> estimated)

Fill estimated measurements with value and derivatives.

Parameters:

quantity - estimated quantity

paramIndices - indices mapping parameter names to derivative indices

estimated - theoretical measurement class