Fixed deserialization of TLE caused by the bStarParameterDriver.

Fixes #851

src/main/java/org/orekit/propagation/analytical/tle/TLE.java

@@ -1014,4 +1014,46 @@ public class TLE implements TimeStamped, Serializable {
         return Collections.singletonList(bStarParameterDriver);
     }
 
+    /** Replace the instance with a data transfer object for serialization.
+     * @return data transfer object that will be serialized
+     */
+    private Object writeReplace() {
+        return new DataTransferObject(line1, line2, utc);
+    }
+
+    /** Internal class used only for serialization. */
+    private static class DataTransferObject implements Serializable {
+
+        /** Serializable UID. */
+        private static final long serialVersionUID = -1596648022319057689L;
+
+        /** First line. */
+        private String line1;
+
+        /** Second line. */
+        private String line2;
+
+        /** The UTC scale. */
+        private final TimeScale utc;
+
+        /** Simple constructor.
+         * @param line1 the first element (69 char String)
+         * @param line2 the second element (69 char String)
+         * @param utc the UTC time scale
+         */
+        DataTransferObject(final String line1, final String line2, final TimeScale utc) {
+            this.line1 = line1;
+            this.line2 = line2;
+            this.utc   = utc;
+        }
+
+        /** Replace the deserialized data transfer object with a {@link TLE}.
+         * @return replacement {@link TLE}
+         */
+        private Object readResolve() {
+            return new TLE(line1, line2, utc);
+        }
+
+    }
+
 }

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

@@ -18,9 +18,13 @@ package org.orekit.propagation.analytical.tle;
 
 
 import java.io.BufferedReader;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
 import java.text.ParseException;
 
 import org.hipparchus.geometry.euclidean.threed.Vector3D;
@@ -28,7 +32,9 @@ import org.hipparchus.util.CombinatoricsUtils;
 import org.hipparchus.util.FastMath;
 import org.junit.Assert;
 import org.junit.Before;
+import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
 import org.orekit.Utils;
 import org.orekit.errors.OrekitException;
 import org.orekit.errors.OrekitMessages;
@@ -48,6 +54,9 @@ import org.orekit.utils.TimeStampedPVCoordinates;
 
 public class TLETest {
 
+    @Rule
+    public TemporaryFolder tempFolder = new TemporaryFolder();
+
     private TLE geoTLE;
 
     private TLE leoTLE;
@@ -648,6 +657,36 @@ public class TLETest {
         Assert.assertEquals(tleISS.getLine2(), rebuilt.getLine2());
     }
 
+    @Test
+    public void testIssue851() throws IOException, ClassNotFoundException {
+
+        // Initialize TLE
+        final TLE tleISS = new TLE("1 25544U 98067A   21035.14486477  .00001026  00000-0  26816-4 0  9998",
+                                   "2 25544  51.6455 280.7636 0002243 335.6496 186.1723 15.48938788267977");
+        String filename = tempFolder.newFile("file.ser").toString();
+
+        // Serialization 
+        FileOutputStream fileSer = new FileOutputStream(filename);
+        ObjectOutputStream outSer = new ObjectOutputStream(fileSer);
+        outSer.writeObject(tleISS);
+        outSer.close();
+        fileSer.close();
+
+        // Deserialization
+        TLE rebuilt = null;
+        FileInputStream file = new FileInputStream(filename);
+        ObjectInputStream in = new ObjectInputStream(file);
+        rebuilt = (TLE) in.readObject();
+        in.close();
+        file.close();
+
+        // Verify
+        Assert.assertEquals(tleISS.getLine1(), rebuilt.getLine1());
+        Assert.assertEquals(tleISS.getLine2(), rebuilt.getLine2());
+        Assert.assertEquals(tleISS.getBStar(), rebuilt.getBStar(), 1.0e-15);
+
+    }
+
     @Before
     public void setUp() {
         Utils.setDataRoot("regular-data");