now I want to define a satellite and a ground area, and obtain the time period of the satellite’s sub satellite point trajectory in the ground area. How do I write the specific code?
I already below source code has some mistakes, could you give me the specific code.
source code：
import java.io.File;
import java.util.Locale;
import org.hipparchus.geometry.euclidean.threed.Vector3D;
import org.hipparchus.geometry.spherical.twod.SphericalPolygonsSet;
import org.hipparchus.ode.events.Action;
import org.hipparchus.util.FastMath;
import org.orekit.bodies.BodyShape;
import org.orekit.bodies.GeodeticPoint;
import org.orekit.bodies.OneAxisEllipsoid;
import org.orekit.data.DataContext;
import org.orekit.data.DataProvidersManager;
import org.orekit.data.DirectoryCrawler;
import org.orekit.errors.OrekitException;
import org.orekit.frames.Frame;
import org.orekit.frames.FramesFactory;
import org.orekit.models.earth.tessellation.EllipsoidTessellator;
import org.orekit.orbits.KeplerianOrbit;
import org.orekit.orbits.Orbit;
import org.orekit.propagation.Propagator;
import org.orekit.propagation.SpacecraftState;
import org.orekit.propagation.analytical.KeplerianPropagator;
import org.orekit.propagation.events.GeographicZoneDetector;
import org.orekit.time.AbsoluteDate;
import org.orekit.time.TimeScalesFactory;
import org.orekit.utils.Constants;
import org.orekit.utils.IERSConventions;
import org.orekit.utils.PVCoordinates;
/** Orekit tutorial for special event detection.
- This tutorial shows how to easily check for visibility between a satellite and a ground station.
- @author Pascal Parraud
/
public class RectangularRegionOnEarth {/* Private constructor for utility class. /
private RectangularRegionOnEarth() {
// empty
}/* Program entry point.- @param args program arguments (unused here)
*/
public static void main(final String args) {
try {
// configure Orekit
final File home = new File(System.getProperty(“user.home”));
final File orekitData = new File(home, “orekit-data”);
if (!orekitData.exists()) {
System.err.format(Locale.US, “Failed to find %s folder%n”,
orekitData.getAbsolutePath());
System.err.format(Locale.US, “You need to download %s from %s, unzip it in %s and rename it ‘orekit-data’ for this tutorial to work%n”,
“orekit-data-master.zip”, “https://gitlab.orekit.org/orekit/orekit-data/-/archive/master/orekit-data-master.zip”,
home.getAbsolutePath());
System.exit(1);
}
final DataProvidersManager manager = DataContext.getDefault().getDataProvidersManager();
manager.addProvider(new DirectoryCrawler(orekitData));
- @param args program arguments (unused here)
// Initial state definition : date, orbit
final AbsoluteDate initialDate = new AbsoluteDate(2023, 10, 26, 8, 00, 00.000, TimeScalesFactory.getUTC());
final double mu = 3.986004415e+14; // gravitation coefficient
final Frame inertialFrame = FramesFactory.getEME2000(); // inertial frame for orbit definition
final Vector3D position = new Vector3D(-7518565.475, 4279265.668, 4816446.308);
final Vector3D velocity = new Vector3D(-5463.904, -5533.9672, 50.719);
final PVCoordinates pvCoordinates = new PVCoordinates(position, velocity);
final Orbit initialOrbit = new KeplerianOrbit(pvCoordinates, inertialFrame, initialDate, mu);
// Propagator : consider a simple Keplerian motion
final Propagator kepler = new KeplerianPropagator(initialOrbit);
// Earth and frame
final Frame earthFrame = FramesFactory.getITRF(IERSConventions.IERS_2010, true);
final BodyShape earth = new OneAxisEllipsoid(Constants.WGS84_EARTH_EQUATORIAL_RADIUS,
Constants.WGS84_EARTH_FLATTENING,
earthFrame);
//创建一个地面区域
GeodeticPoint point1 = new GeodeticPoint(Math.toRadians(0), Math.toRadians(30), 0.0);
GeodeticPoint point2 = new GeodeticPoint(Math.toRadians(30), Math.toRadians(30), 0.0);
GeodeticPoint point3 = new GeodeticPoint(Math.toRadians(30), Math.toRadians(0), 0.0);
GeodeticPoint point4 = new GeodeticPoint(Math.toRadians(0), Math.toRadians(0), 0.0);
// 创建表示地面区域的SphericalPolygonsSet
SphericalPolygonsSet region = EllipsoidTessellator.buildSimpleZone(1.0e-10, point1, point2, point3, point4);
// Event definition
final double maxcheck = 60;
final double threshold = 0.001;
final double elevation = FastMath.toRadians(0.0);
final GeographicZoneDetector zoneDetector = new GeographicZoneDetector(maxcheck, threshold, earth, region, elevation)
.withHandler((s, detector, increasing) -> {
if (increasing) {
System.out.println("Visibility begins at " + s.getDate());
} else {
System.out.println("Visibility ends at " + s.getDate());
System.out.println();
}
return Action.CONTINUE; // Continue processing the event
});
// Add event to be detected
kepler.addEventDetector(zoneDetector);
// Propagate from the initial date to the first raising or for the fixed duration
final SpacecraftState finalState = kepler.propagate(initialDate.shiftedBy(360000.));
System.out.println(" Final state : " + finalState.getDate().durationFrom(initialDate));
} catch (OrekitException oe) {
System.err.println(oe.getLocalizedMessage());
}
}
}
Cheers,
Yang