@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);
}
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 testEphemerisDatesBackward() throws OrekitException {
// setup
TimeScale tai = TimeScalesFactory.getTAI();
AbsoluteDate initialDate = new AbsoluteDate("2015-07-05", tai);
AbsoluteDate startDate = new AbsoluteDate("2015-07-03", tai).shiftedBy(-0.1);
AbsoluteDate endDate = new AbsoluteDate("2015-07-04", tai);
Frame eci = FramesFactory.getGCRF();
KeplerianOrbit orbit =
new KeplerianOrbit(
600e3 + Constants.WGS84_EARTH_EQUATORIAL_RADIUS,
0,
0,
0,
0,
0,
PositionAngle.TRUE,
eci,
initialDate,
mu);
double[][] tol = NumericalPropagator.tolerances(1, orbit, OrbitType.CARTESIAN);
Propagator prop =
new NumericalPropagator(new DormandPrince853Integrator(0.1, 500, tol[0], tol[1]));
prop.resetInitialState(new SpacecraftState(new CartesianOrbit(orbit)));
// action
prop.setEphemerisMode();
prop.propagate(endDate, startDate);
BoundedPropagator ephemeris = prop.getGeneratedEphemeris();
// verify
TimeStampedPVCoordinates actualPV = ephemeris.getPVCoordinates(startDate, eci);
TimeStampedPVCoordinates expectedPV = orbit.getPVCoordinates(startDate, eci);
MatcherAssert.assertThat(
actualPV.getPosition(), OrekitMatchers.vectorCloseTo(expectedPV.getPosition(), 1.0));
MatcherAssert.assertThat(
actualPV.getVelocity(), OrekitMatchers.vectorCloseTo(expectedPV.getVelocity(), 1.0));
MatcherAssert.assertThat(
ephemeris.getMinDate().durationFrom(startDate), OrekitMatchers.closeTo(0, 0));
MatcherAssert.assertThat(
ephemeris.getMaxDate().durationFrom(endDate), OrekitMatchers.closeTo(0, 0));
// test date
AbsoluteDate date = endDate.shiftedBy(-0.11);
Assert.assertEquals(ephemeris.propagate(date).getDate().durationFrom(date), 0, 0);
}
/**
* 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 testGroundProjectionTaylor() 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);
Orbit orbit = new EquinoctialOrbit(initPV, eme2000, Constants.EIGEN5C_EARTH_MU);
TimeStampedPVCoordinates pv0 = orbit.getPVCoordinates(orbit.getDate(), model.getBodyFrame());
PVCoordinatesProvider groundTaylor =
model.projectToGround(pv0, model.getBodyFrame()).toTaylorProvider(model.getBodyFrame());
TimeStampedPVCoordinates g0 =
groundTaylor.getPVCoordinates(orbit.getDate(), model.getBodyFrame());
Vector3D zenith = pv0.getPosition().subtract(g0.getPosition()).normalize();
Vector3D acrossTrack = Vector3D.crossProduct(zenith, g0.getVelocity()).normalize();
Vector3D alongTrack = Vector3D.crossProduct(acrossTrack, zenith).normalize();
for (double dt = -1; dt < 1; dt += 0.01) {
AbsoluteDate date = orbit.getDate().shiftedBy(dt);
Vector3D taylorP = groundTaylor.getPVCoordinates(date, model.getBodyFrame()).getPosition();
Vector3D refP =
model.projectToGround(
orbit.getPVCoordinates(date, model.getBodyFrame()).getPosition(),
date,
model.getBodyFrame());
Vector3D delta = taylorP.subtract(refP);
Assert.assertEquals(0.0, Vector3D.dotProduct(delta, alongTrack), 0.0015);
Assert.assertEquals(0.0, Vector3D.dotProduct(delta, acrossTrack), 0.0007);
Assert.assertEquals(0.0, Vector3D.dotProduct(delta, zenith), 0.00002);
}
}