TLE Generator from Ephemeris Data

Main.java

// Orekit Libraries
import org.orekit.files.ccsds.*;
import org.orekit.propagation.analytical.tle.TLE;
import org.orekit.propagation.analytical.tle.TLEPropagator;
import org.orekit.propagation.conversion.FiniteDifferencePropagatorConverter;
import org.orekit.propagation.conversion.TLEPropagatorBuilder;
import org.orekit.time.*;
import org.orekit.data.*;
import org.orekit.orbits.*;
import org.orekit.propagation.*;

// Java Libraries
import java.io.*;
import java.util.*;

public class Main {

    public static void main(String[] args) {
        try {
            // CONFIGURATION
            File orekitData = new File("Libraries/orekit-data");
            DataProvidersManager manager = DataProvidersManager.getInstance();
            manager.addProvider(new DirectoryCrawler(orekitData));

            int launchNum = 12, launchYear = 2018; // Made up

            OEMParser parser = new OEMParser();
            parser = parser.withInternationalDesignator(launchYear,launchNum,"UUU");
            OEMFile file = parser.parse("EphemerisData.oem");

            List<OEMFile.EphemeridesBlock> ephemeridesBlockList = file.getEphemeridesBlocks();
            OEMFile.EphemeridesBlock block = ephemeridesBlockList.get(0);
            BoundedPropagator boundedPropagator = block.getPropagator();
            List<SpacecraftState> spacecraftStateList = new ArrayList<>();

            for (AbsoluteDate date = block.getStart(); date.compareTo(block.getStop()) <= 0; date = date.shiftedBy(60)) {
                spacecraftStateList.add(boundedPropagator.propagate(date));
            }
            
            // Data for the template TLE
            KeplerianOrbit kOrbit = new KeplerianOrbit(spacecraftStateList.get(0).getOrbit());
            double pa = kOrbit.getPerigeeArgument();
            System.out.println("Perigee Argument: " + pa);
            double raan = kOrbit.getRightAscensionOfAscendingNode();
            //double raan = Math.toRadians(10.0);
            System.out.println("RAAN: " + Math.toDegrees(raan));
            double inc = spacecraftStateList.get(0).getI();//Math.toRadians(98.17);
            System.out.println("Inc: " + Math.toDegrees(inc));
            double meanMotion = spacecraftStateList.get(0).getKeplerianMeanMotion();
            System.out.println("Mean motion: " + meanMotion);
            AbsoluteDate epoch = spacecraftStateList.get(0).getDate();
            System.out.println("Epoch: " + epoch);
            double eccentricity = spacecraftStateList.get(0).getOrbit().getE();
            double meanMotFirstDeriv = (spacecraftStateList.get(1).getKeplerianMeanMotion() - meanMotion) / 60;
            System.out.println("Mean Motion 1st derivative: " + meanMotFirstDeriv);
            double meanMotSecondDeriv = ((spacecraftStateList.get(2).getKeplerianMeanMotion() -
                    spacecraftStateList.get(1).getKeplerianMeanMotion()) / 60 - meanMotFirstDeriv) / 60;
            System.out.println("Mean Motion 2nd derivative: " + meanMotSecondDeriv);
            double meanAnomaly = kOrbit.getMeanAnomaly();
            System.out.println("Mean Anomaly: " + meanAnomaly);

            System.out.println("Launch number: " + launchNum);
            System.out.println("Launch year: " + launchYear);

            FiniteDifferencePropagatorConverter converter =
                    new FiniteDifferencePropagatorConverter(new TLEPropagatorBuilder(
                            new TLE(99998,'U',launchYear,launchNum,"UUU",
                                    2,1, epoch, meanMotion,
                                    meanMotFirstDeriv,meanMotSecondDeriv,eccentricity,inc,pa,
                                    raan,meanAnomaly,0,0),
                            PositionAngle.MEAN,1.0),0.01,6000000);

            System.out.println("Calculating TLE...");

            TLEPropagator tlePropagator = (TLEPropagator) converter.convert(spacecraftStateList,false,"BSTAR");

            System.out.println(tlePropagator.getTLE());

        } catch (Exception e) {
            System.out.println("Error: " + e);
        }
    }
}

This might help, this guy did exactly that (OEM -> TLE):
http://pictures.ed-morana.com/ISSTransits/predictions/ISSTransitPredictionDetails.html#OptionalData

Hey,
Didi you find a solution for your problem? Is the code above runnable?

Hey,
Didi you find a solution for your problem? Is the code above runnable?

I think I did find a solution but I don't even remember the details of the problem I was having, this was 5 years ago... You can try to run it, but I wouldn't bet on it being correct.