org.orekit.estimation.measurements

Class InterSatellitesRange

java.lang.Object

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

org.orekit.estimation.measurements.InterSatellitesRange

All Implemented Interfaces:

Comparable<ComparableMeasurement>, ComparableMeasurement, ObservedMeasurement<InterSatellitesRange>, TimeStamped

public class InterSatellitesRange
extends AbstractMeasurement<InterSatellitesRange>

One-way or two-way range measurements between two satellites.

For one-way measurements, a signal is emitted by a remote satellite and received by local satellite. The measurement value is the elapsed time between emission and reception multiplied by c where c is the speed of light.

For two-way measurements, a signal is emitted by local satellite, reflected on remote satellite, and received back by local satellite. The measurement value is the elapsed time between emission and reception multiplied by c/2 where c is the speed of light.

Since 9.3, this class also uses the clock offsets of both satellites, which manage the value that must be added to each satellite reading of time to compute the real physical date. In this measurement, these offsets have two effects:

• as measurement date is evaluated at reception time, the real physical date of the measurement is the observed date to which the local satellite clock offset is subtracted
• as range is evaluated using the total signal time of flight, for one-way measurements the observed range is the real physical signal time of flight to which (Δtl - Δtr) ⨉ c is added, where Δtl (resp. Δtr) is the clock offset for the local satellite (resp. remote satellite). A similar effect exists in two-way measurements but it is computed as (Δtl - Δtl) ⨉ c / 2 as the local satellite clock is used for both initial emission and final reception and therefore it evaluates to zero.

The motion of both satellites during the signal flight time is taken into account. The date of the measurement corresponds to the reception of the signal by satellite 1.

Since:

9.0

Author:

Luc Maisonobe

Constructor Summary

Constructors

Constructor and Description
InterSatellitesRange(ObservableSatellite local, ObservableSatellite remote, boolean twoWay, AbsoluteDate date, double range, double sigma, double baseWeight) Simple constructor.

Method Summary

Modifier and Type	Method and Description
boolean	isTwoWay() Check if the instance represents a two-way measurement.
protected EstimatedMeasurement<InterSatellitesRange>	theoreticalEvaluation(int iteration, int evaluation, SpacecraftState[] states) Estimate the theoretical value.

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

addModifier, addParameterDriver, estimate, getBaseWeight, getCoordinates, getDate, getDimension, getModifiers, getObservedValue, getParametersDrivers, getSatellites, getTheoreticalStandardDeviation, isEnabled, setEnabled, signalTimeOfFlight, signalTimeOfFlight

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

Constructor Detail

InterSatellitesRange

public InterSatellitesRange(ObservableSatellite local,
                            ObservableSatellite remote,
                            boolean twoWay,
                            AbsoluteDate date,
                            double range,
                            double sigma,
                            double baseWeight)

Simple constructor.

Parameters:

local - satellite which receives the signal and performs the measurement

remote - satellite which simply emits the signal in the one-way case, or reflects the signal in the two-way case

twoWay - flag indicating whether it is a two-way measurement

date - date of the measurement

range - observed value

sigma - theoretical standard deviation

baseWeight - base weight

Since:

9.3

Method Detail

isTwoWay

public boolean isTwoWay()

Check if the instance represents a two-way measurement.

Returns:

true if the instance represents a two-way measurement

theoreticalEvaluation

protected EstimatedMeasurement<InterSatellitesRange> 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<InterSatellitesRange>

Parameters:

iteration - iteration number

evaluation - evaluation number

states - orbital states at measurement date

Returns:

theoretical value

See Also:

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