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(),
};
}
/** {@inheritDoc} */
protected TimeStampedPVCoordinates getTargetPV(
final PVCoordinatesProvider pvProv, final AbsoluteDate date, final Frame frame)
throws OrekitException {
// transform from specified reference frame to spacecraft frame
final Transform refToSc =
new Transform(
date,
new Transform(date, pvProv.getPVCoordinates(date, frame).negate()),
new Transform(date, attitudeLaw.getAttitude(pvProv, date, frame).getOrientation()));
// transform from specified reference frame to body frame
final Transform refToBody = frame.getTransformTo(shape.getBodyFrame(), date);
// sample intersection points in current date neighborhood
final Transform scToBody = new Transform(date, refToSc.getInverse(), refToBody);
final double h = 0.1;
final List<TimeStampedPVCoordinates> sample = new ArrayList<TimeStampedPVCoordinates>();
sample.add(losIntersectionWithBody(scToBody.shiftedBy(-h)));
sample.add(losIntersectionWithBody(scToBody));
sample.add(losIntersectionWithBody(scToBody.shiftedBy(+h)));
// use interpolation to compute properly the time-derivatives
final TimeStampedPVCoordinates targetBody =
TimeStampedPVCoordinates.interpolate(date, CartesianDerivativesFilter.USE_P, sample);
// convert back to caller specified frame
return refToBody.getInverse().transformPVCoordinates(targetBody);
}