private double[] derivativesErrors(
PVCoordinatesProvider provider, AbsoluteDate date, Frame frame, OneAxisEllipsoid model)
throws OrekitException {
List<TimeStampedPVCoordinates> pvList = new ArrayList<TimeStampedPVCoordinates>();
List<TimeStampedPVCoordinates> groundPVList = new ArrayList<TimeStampedPVCoordinates>();
for (double dt = -0.25; dt <= 0.25; dt += 0.125) {
TimeStampedPVCoordinates shiftedPV = provider.getPVCoordinates(date.shiftedBy(dt), frame);
Vector3D p = model.projectToGround(shiftedPV.getPosition(), shiftedPV.getDate(), frame);
pvList.add(shiftedPV);
groundPVList.add(
new TimeStampedPVCoordinates(shiftedPV.getDate(), p, Vector3D.ZERO, Vector3D.ZERO));
}
TimeStampedPVCoordinates computed =
model.projectToGround(
TimeStampedPVCoordinates.interpolate(date, CartesianDerivativesFilter.USE_P, pvList),
frame);
TimeStampedPVCoordinates reference =
TimeStampedPVCoordinates.interpolate(date, CartesianDerivativesFilter.USE_P, groundPVList);
TimeStampedPVCoordinates pv0 = provider.getPVCoordinates(date, frame);
Vector3D p0 = pv0.getPosition();
Vector3D v0 = pv0.getVelocity();
Vector3D a0 = pv0.getAcceleration();
return new double[] {
Vector3D.distance(computed.getPosition(), reference.getPosition()) / p0.getNorm(),
Vector3D.distance(computed.getVelocity(), reference.getVelocity()) / v0.getNorm(),
Vector3D.distance(computed.getAcceleration(), reference.getAcceleration()) / a0.getNorm(),
};
}
@Test
public void testGroundToGroundIssue181() throws OrekitException {
Frame itrf = FramesFactory.getITRF(IERSConventions.IERS_2010, true);
Frame eme2000 = FramesFactory.getEME2000();
OneAxisEllipsoid model =
new OneAxisEllipsoid(
Constants.WGS84_EARTH_EQUATORIAL_RADIUS, Constants.WGS84_EARTH_FLATTENING, itrf);
TimeStampedPVCoordinates initPV =
new TimeStampedPVCoordinates(
AbsoluteDate.J2000_EPOCH.shiftedBy(584.),
new Vector3D(3220103., 69623., 6449822.),
new Vector3D(6414.7, -2006., -3180.),
Vector3D.ZERO);
TimeStampedPVCoordinates body =
itrf.getTransformTo(eme2000, initPV.getDate()).transformPVCoordinates(initPV);
TimeStampedPVCoordinates ground1 = model.projectToGround(body, itrf);
TimeStampedPVCoordinates ground2 = model.projectToGround(ground1, itrf);
Assert.assertEquals(
0.0, Vector3D.distance(ground1.getPosition(), ground2.getPosition()), 1.0e-12);
Assert.assertEquals(
0.0, Vector3D.distance(ground1.getVelocity(), ground2.getVelocity()), 1.0e-12);
Assert.assertEquals(
0.0, Vector3D.distance(ground1.getAcceleration(), ground2.getAcceleration()), 1.0e-12);
}
/**
* Set the orbit from Cartesian parameters.
*
* <p>The acceleration provided in {@code pvCoordinates} is accessible using {@link
* #getPVCoordinates()} and {@link #getPVCoordinates(Frame)}. All other methods use {@code mu} and
* the position to compute the acceleration, including {@link #shiftedBy(double)} and {@link
* #getPVCoordinates(AbsoluteDate, Frame)}.
*
* @param pvCoordinates the position and velocity in the inertial frame
* @param frame the frame in which the {@link TimeStampedPVCoordinates} are defined (<em>must</em>
* be a {@link Frame#isPseudoInertial pseudo-inertial frame})
* @param mu central attraction coefficient (m^3/s^2)
* @exception IllegalArgumentException if frame is not a {@link Frame#isPseudoInertial
* pseudo-inertial frame}
*/
protected Orbit(final TimeStampedPVCoordinates pvCoordinates, final Frame frame, final double mu)
throws IllegalArgumentException {
ensurePseudoInertialFrame(frame);
this.date = pvCoordinates.getDate();
this.mu = mu;
if (pvCoordinates.getAcceleration().getNormSq() == 0) {
// the acceleration was not provided,
// compute it from Newtonian attraction
final double r2 = pvCoordinates.getPosition().getNormSq();
final double r3 = r2 * FastMath.sqrt(r2);
this.pvCoordinates =
new TimeStampedPVCoordinates(
pvCoordinates.getDate(),
pvCoordinates.getPosition(),
pvCoordinates.getVelocity(),
new Vector3D(-mu / r3, pvCoordinates.getPosition()));
} else {
this.pvCoordinates = pvCoordinates;
}
this.frame = frame;
}
@Test
public void testGroundProjectionPosition() throws OrekitException {
OneAxisEllipsoid model =
new OneAxisEllipsoid(
Constants.WGS84_EARTH_EQUATORIAL_RADIUS,
Constants.WGS84_EARTH_FLATTENING,
FramesFactory.getITRF(IERSConventions.IERS_2010, true));
TimeStampedPVCoordinates initPV =
new TimeStampedPVCoordinates(
AbsoluteDate.J2000_EPOCH.shiftedBy(584.),
new Vector3D(3220103., 69623., 6449822.),
new Vector3D(6414.7, -2006., -3180.),
Vector3D.ZERO);
Frame eme2000 = FramesFactory.getEME2000();
Orbit orbit = new EquinoctialOrbit(initPV, eme2000, Constants.EIGEN5C_EARTH_MU);
for (double dt = 0; dt < 3600.0; dt += 60.0) {
TimeStampedPVCoordinates pv = orbit.getPVCoordinates(orbit.getDate().shiftedBy(dt), eme2000);
TimeStampedPVCoordinates groundPV = model.projectToGround(pv, eme2000);
Vector3D groundP = model.projectToGround(pv.getPosition(), pv.getDate(), eme2000);
// check methods projectToGround and transform are consistent with each other
Assert.assertEquals(
model.transform(pv.getPosition(), eme2000, pv.getDate()).getLatitude(),
model.transform(groundPV.getPosition(), eme2000, pv.getDate()).getLatitude(),
1.0e-10);
Assert.assertEquals(
model.transform(pv.getPosition(), eme2000, pv.getDate()).getLongitude(),
model.transform(groundPV.getPosition(), eme2000, pv.getDate()).getLongitude(),
1.0e-10);
Assert.assertEquals(
0.0, Vector3D.distance(groundP, groundPV.getPosition()), 1.0e-15 * groundP.getNorm());
}
}