/** * Compute mean state from osculating state. * * <p>Compute in a DSST sense the mean state corresponding to the input osculating state. * * <p>The computing is done through a fixed-point iteration process. * * @param osculating initial osculating state * @return mean state * @throws OrekitException if the underlying computation of short periodic variation fails */ private Orbit computeMeanOrbit(final SpacecraftState osculating) throws OrekitException { // rough initialization of the mean parameters EquinoctialOrbit meanOrbit = new EquinoctialOrbit(osculating.getOrbit()); // threshold for each parameter final double epsilon = 1.0e-13; final double thresholdA = epsilon * (1 + FastMath.abs(meanOrbit.getA())); final double thresholdE = epsilon * (1 + meanOrbit.getE()); final double thresholdAngles = epsilon * FastMath.PI; int i = 0; while (i++ < 200) { final SpacecraftState meanState = new SpacecraftState(meanOrbit, osculating.getAttitude(), osculating.getMass()); // recompute the osculating parameters from the current mean parameters final EquinoctialOrbit rebuilt = (EquinoctialOrbit) computeOsculatingOrbit(meanState); // adapted parameters residuals final double deltaA = osculating.getA() - rebuilt.getA(); final double deltaEx = osculating.getEquinoctialEx() - rebuilt.getEquinoctialEx(); final double deltaEy = osculating.getEquinoctialEy() - rebuilt.getEquinoctialEy(); final double deltaHx = osculating.getHx() - rebuilt.getHx(); final double deltaHy = osculating.getHy() - rebuilt.getHy(); final double deltaLm = MathUtils.normalizeAngle(osculating.getLM() - rebuilt.getLM(), 0.0); // check convergence if ((FastMath.abs(deltaA) < thresholdA) && (FastMath.abs(deltaEx) < thresholdE) && (FastMath.abs(deltaEy) < thresholdE) && (FastMath.abs(deltaLm) < thresholdAngles)) { return meanOrbit; } // update mean parameters meanOrbit = new EquinoctialOrbit( meanOrbit.getA() + deltaA, meanOrbit.getEquinoctialEx() + deltaEx, meanOrbit.getEquinoctialEy() + deltaEy, meanOrbit.getHx() + deltaHx, meanOrbit.getHy() + deltaHy, meanOrbit.getLM() + deltaLm, PositionAngle.MEAN, meanOrbit.getFrame(), meanOrbit.getDate(), meanOrbit.getMu()); } throw new PropagationException(OrekitMessages.UNABLE_TO_COMPUTE_DSST_MEAN_PARAMETERS, i); }
private void checkCartesianToEllipsoidic( double ae, double f, double x, double y, double z, double longitude, double latitude, double altitude) throws OrekitException { AbsoluteDate date = AbsoluteDate.J2000_EPOCH; Frame frame = FramesFactory.getITRF(IERSConventions.IERS_2010, true); OneAxisEllipsoid model = new OneAxisEllipsoid(ae, f, frame); GeodeticPoint gp = model.transform(new Vector3D(x, y, z), frame, date); Assert.assertEquals(longitude, MathUtils.normalizeAngle(gp.getLongitude(), longitude), 1.0e-10); Assert.assertEquals(latitude, gp.getLatitude(), 1.0e-10); Assert.assertEquals(altitude, gp.getAltitude(), 1.0e-10 * FastMath.abs(ae)); Vector3D rebuiltNadir = Vector3D.crossProduct(gp.getSouth(), gp.getWest()); Assert.assertEquals(0, rebuiltNadir.subtract(gp.getNadir()).getNorm(), 1.0e-15); }