Package org.orekit.time

Class SatelliteClockScale

java.lang.Object

org.orekit.time.SatelliteClockScale

All Implemented Interfaces:

TimeScale

public class SatelliteClockScale
extends Object
implements TimeScale

Scale for on-board clock.

Since:

11.0

Author:

Luc Maisonobe

Constructor Summary

Constructors

Constructor	Description
SatelliteClockScale(String name, AbsoluteDate epoch, TimeScale epochScale, double countAtEpoch, double drift)	Create a linear model for satellite clock.

Method Summary

Modifier and Type	Method	Description
double	countAtDate(AbsoluteDate date)	Compute clock count corresponding to some date.
AbsoluteDate	dateAtCount(double count)	Compute date corresponding to some clock count.
String	getName()	Get the name time scale.
TimeOffset	offsetFromTAI(AbsoluteDate date)	Get the offset to convert locations from TAIScale to instance.
<T extends CalculusFieldElement<T>> T	offsetFromTAI(FieldAbsoluteDate<T> date)	Get the offset to convert locations from TAIScale to instance.
TimeOffset	offsetToTAI(DateComponents date, TimeComponents time)	Get the offset to convert locations from instance to TAIScale.
String	toString()

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.orekit.time.TimeScale

getLeap, getLeap, insideLeap, insideLeap, minuteDuration, minuteDuration

Constructor Details

SatelliteClockScale

public SatelliteClockScale(String name,
 AbsoluteDate epoch,
 TimeScale epochScale,
 double countAtEpoch,
 double drift)

Create a linear model for satellite clock.

Beware that we specify the model using its drift with respect to flow of time. For a perfect clock without any drift, the clock count would be one tick every SI second. A clock that is fast, say for example it generates 1000001 ticks every 1000000 SI second, would have a rate of 1.000001 tick per SI second and hence a drift of 1.0e-6 tick per SI second. In this constructor we use the drift (1.0e-6 in the previous example) rather than the rate (1.000001 in the previous example) to specify the clock. The rationale is that for clocks that are intended to be used for representing absolute time, the drift is expected to be small (much smaller that 1.0e-6 for a good clock), so using drift is numerically more stable than using rate and risking catastrophic cancellation when subtracting 1.0 in the internal computation.

Despite what is explained in the previous paragraph, this class can handle spacecraft clocks that are not intended to be synchronized with SI seconds, for example clocks that ticks at 10 Hz. In such cases the drift would need to be set at 10.0 - 1.0 = 9.0, which is not intuitive. For these clocks, the methods countAtDate(AbsoluteDate) and dateAtCount(double) and perhaps offsetFromTAI(AbsoluteDate) are still useful, whereas offsetToTAI(DateComponents, TimeComponents) is probably not really meaningful.

Parameters:

name - of the scale

epoch - reference epoch

epochScale - time scale in which the epoch was defined

countAtEpoch - clock count at epoch

drift - clock drift rate (i.e. clock count change per SI second minus 1.0)

Method Details

offsetFromTAI

public TimeOffset offsetFromTAI(AbsoluteDate date)

Get the offset to convert locations from TAIScale to instance.

Specified by:

offsetFromTAI in interface TimeScale

Parameters:

date - conversion date

Returns:

offset in seconds to add to a location in TAIScale time scale to get a location in instance time scale

See Also:

• TimeScale.offsetToTAI(DateComponents, TimeComponents)

offsetToTAI

public TimeOffset offsetToTAI(DateComponents date,
 TimeComponents time)

Get the offset to convert locations from instance to TAIScale.

Specified by:

offsetToTAI in interface TimeScale

Parameters:

date - date location in the time scale

time - time location in the time scale

Returns:

offset in seconds to add to a location in instance time scale to get a location in TAIScale time scale

See Also:

• TimeScale.offsetFromTAI(AbsoluteDate)

dateAtCount

public AbsoluteDate dateAtCount(double count)

Compute date corresponding to some clock count.

Parameters:

count - clock count

Returns:

date at count

countAtDate

public double countAtDate(AbsoluteDate date)

Compute clock count corresponding to some date.

Parameters:

date - date

Returns:

clock count at date

offsetFromTAI

public <T extends CalculusFieldElement<T>> T offsetFromTAI(FieldAbsoluteDate<T> date)

Get the offset to convert locations from TAIScale to instance.

Specified by:

offsetFromTAI in interface TimeScale

Type Parameters:

T - type of the filed elements

Parameters:

date - conversion date

Returns:

offset in seconds to add to a location in TAIScale time scale to get a location in instance time scale

See Also:

• TimeScale.offsetToTAI(DateComponents, TimeComponents)

getName

public String getName()

Get the name time scale.

Specified by:

getName in interface TimeScale

Returns:

name of the time scale

toString

public String toString()

Overrides:

toString in class Object