org.orekit.estimation.measurements

Class Range

java.lang.Object

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

org.orekit.estimation.measurements.Range

All Implemented Interfaces:

Comparable<ComparableMeasurement>, ComparableMeasurement, ObservedMeasurement<Range>, TimeStamped

public class Range
extends AbstractMeasurement<Range>

Class modeling a range measurement from a ground station.

For one-way measurements, a signal is emitted by the satellite and received by the ground station. 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, the measurement is considered to be a signal emitted from a ground station, reflected on spacecraft, and received on the same ground station. Its value is the elapsed time between emission and reception multiplied by c/2 where c is the speed of light.

The motion of both the station and the spacecraft during the signal flight time are taken into account. The date of the measurement corresponds to the reception on ground of the emitted or reflected signal.

The clock offsets of both the ground station and the satellite are taken into account. These offsets correspond to the values that must be subtracted from station (resp. satellite) reading of time to compute the real physical date. 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 receiving ground station 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 (Δtg - Δts) ⨉ c is added, where Δtg (resp. Δts) is the clock offset for the receiving ground station (resp. emitting satellite). A similar effect exists in two-way measurements but it is computed as (Δtg - Δtg) ⨉ c / 2 as the same ground station clock is used for initial emission and final reception and therefore it evaluates to zero.

Since:

8.0

Author:

Thierry Ceolin, Luc Maisonobe, Maxime Journot

Constructor Summary

Constructors

Constructor and Description
Range(GroundStation station, boolean twoWay, AbsoluteDate date, double range, double sigma, double baseWeight, ObservableSatellite satellite) Simple constructor.

Method Summary

Modifier and Type	Method and Description
GroundStation	getStation() Get the ground station from which measurement is performed.
boolean	isTwoWay() Check if the instance represents a two-way measurement.
protected EstimatedMeasurement<Range>	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

Range

public Range(GroundStation station,
             boolean twoWay,
             AbsoluteDate date,
             double range,
             double sigma,
             double baseWeight,
             ObservableSatellite satellite)

Simple constructor.

Parameters:

station - ground station from which measurement is performed

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

satellite - satellite related to this measurement

Since:

9.3

Method Detail

getStation

public GroundStation getStation()

Get the ground station from which measurement is performed.

Returns:

ground station from which measurement is performed

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<Range> 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<Range>

Parameters:

iteration - iteration number

evaluation - evaluation number

states - orbital states at measurement date

Returns:

theoretical value

See Also:

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