Test case for issue #724

src/test/java/org/orekit/propagation/analytical/tle/TLEFittingIssue.java

+package org.orekit.propagation.analytical.tle;
+
+import java.util.ArrayList;
+
+import org.junit.Test;
+import org.orekit.Utils;
+import org.orekit.frames.Frame;
+import org.orekit.frames.FramesFactory;
+import org.orekit.orbits.CartesianOrbit;
+import org.orekit.orbits.PositionAngle;
+import org.orekit.propagation.SpacecraftState;
+import org.orekit.propagation.analytical.KeplerianPropagator;
+import org.orekit.propagation.conversion.FiniteDifferencePropagatorConverter;
+import org.orekit.propagation.conversion.TLEPropagatorBuilder;
+import org.orekit.time.AbsoluteDate;
+import org.orekit.time.TimeScale;
+import org.orekit.time.TimeScalesFactory;
+import org.orekit.utils.Constants;
+import org.orekit.utils.IERSConventions;
+import org.orekit.utils.PVCoordinates;
+import org.hipparchus.geometry.euclidean.threed.Vector3D;
+import org.hipparchus.util.FastMath;
+
+public class TLEFittingIssue {
+
+    @Test
+    public void test() {
+
+        Utils.setDataRoot("regular-data");
+
+        int satellite_number = 99999;
+        char classification = 'U';
+        int launch_year = 2020;
+        int launch_number = 1;
+        String launch_piece = "a";
+        int ephemeris_type = 0;
+        int element_number = 1;
+        int revolution_number = 1;
+        double mean_motion_first_derivative = 0.0;
+        double mean_motion_second_derivative = 0.0;
+        double b_star_first_guess = 1e-5;
+
+        TimeScale utc = TimeScalesFactory.getUTC();
+        Frame itrf = FramesFactory.getITRF(IERSConventions.IERS_2010, true);
+        Frame gcrf = FramesFactory.getGCRF();
+
+        AbsoluteDate launchDate = new AbsoluteDate(2020, 9, 28, 11, 20, 32.0, utc);
+        AbsoluteDate separationDate = launchDate.shiftedBy(12340.0);
+
+        Frame launchFrame = itrf.getFrozenFrame(gcrf, launchDate, "launchFrame");
+
+        Vector3D pos_init = new Vector3D(6048.107, 3025.385, 1585.042).scalarMultiply(1e3);
+        Vector3D vel_init = new Vector3D(-1.068882, -1.694130, 7.304083).scalarMultiply(1e3);
+        PVCoordinates pvInit = new PVCoordinates(pos_init, vel_init);
+
+        CartesianOrbit initialOrbit = new CartesianOrbit(pvInit, launchFrame, separationDate,
+                Constants.EIGEN5C_EARTH_MU);
+
+        KeplerianPropagator propagator = new KeplerianPropagator(initialOrbit);
+
+        ArrayList<SpacecraftState> states_list = new ArrayList<SpacecraftState>();
+
+        double dt = 60.0;
+        AbsoluteDate date_current = separationDate;
+
+        while (date_current.compareTo(separationDate.shiftedBy(24 * 3600.0)) <= 0) {
+            states_list.add(propagator.propagate(date_current));
+            date_current = date_current.shiftedBy(dt);
+        }
+
+        TLE tle_first_guess = new TLE(satellite_number, classification, launch_year, launch_number, launch_piece,
+                ephemeris_type, element_number, initialOrbit.getDate(), initialOrbit.getKeplerianMeanMotion(),
+                mean_motion_first_derivative, mean_motion_second_derivative, initialOrbit.getE(), initialOrbit.getI(),
+                0.0, 0.0, 0.0, revolution_number, b_star_first_guess);
+
+        double threshold = 1.0;
+        TLEPropagatorBuilder tle_builder = new TLEPropagatorBuilder(tle_first_guess, PositionAngle.MEAN, 1.0);
+        FiniteDifferencePropagatorConverter fitter = new FiniteDifferencePropagatorConverter(tle_builder, threshold,
+                10000);
+        fitter.convert(states_list, false, "BSTAR");
+        TLEPropagator tle_propagator = (TLEPropagator) fitter.getAdaptedPropagator();
+        TLE tle_fitted = tle_propagator.getTLE();
+    }
+}