Hello,
I have noticed an inconsistency in TimeStampedDouble and TimeStampedDoubleAndDerivative. In most other TimeStampedXXX classes, the date is the first argument given, such as in TimeStampedPVCoordinates, TimeStampedAngularCoordinates, and TimeStampedSphericalHarmonics for example.
It might be good to have homogeneous argument order between similar classes. It’s generally easier to use a library when the same types arrive in the same order, and also it looks nicer 
.
I also needed a TimeStampedGeodeticPoint in my project to store a timed ground track of a satellite. It might also be useful for someone else, and could be added to a future version of Orekit.
package org.orekit.bodies;
import org.orekit.time.AbsoluteDate;
import org.orekit.time.TimeStamped;
/**
* Implements a time-stamped {@link GeodeticPoint}.
*/
public class TimeStampedGeodeticPoint extends GeodeticPoint implements TimeStamped {
/// Date at which the {@link GeodeticPoint} is set.
final AbsoluteDate date;
/**
* Build a new instance from geodetic coordinates.
*
* @param date date of the point
* @param latitude geodetic latitude (rad)
* @param longitude geodetic longitude (rad)
* @param altitude altitude above ellipsoid (m)
*/
public TimeStampedGeodeticPoint(final AbsoluteDate date, final double latitude, final double longitude, final double altitude) {
super(latitude, longitude, altitude);
this.date = date;
}
/**
* Build a new instance from a {@link GeodeticPoint}.
*
* @param date date of the point
* @param point geodetic point
*/
public TimeStampedGeodeticPoint(final AbsoluteDate date, final GeodeticPoint point) {
super(point.getLatitude(), point.getLongitude(), point.getAltitude());
this.date = date;
}
@Override
public AbsoluteDate getDate() {
return date;
}
}
!