Issue #615: Added addAdditionalEquations() in AbstractPropagatorBuilder.

src/main/java/org/orekit/propagation/conversion/AbstractPropagatorBuilder.java

@@ -16,16 +16,20 @@
  */
 package org.orekit.propagation.conversion;
 
+import java.util.ArrayList;
 import java.util.List;
 
 import org.hipparchus.exception.LocalizedCoreFormats;
 import org.hipparchus.util.FastMath;
+import org.orekit.errors.OrekitException;
+import org.orekit.errors.OrekitMessages;
 import org.orekit.errors.OrekitIllegalArgumentException;
 import org.orekit.forces.gravity.NewtonianAttraction;
 import org.orekit.frames.Frame;
 import org.orekit.orbits.Orbit;
 import org.orekit.orbits.OrbitType;
 import org.orekit.orbits.PositionAngle;
+import org.orekit.propagation.integration.AdditionalEquations;
 import org.orekit.time.AbsoluteDate;
 import org.orekit.utils.ParameterDriver;
 import org.orekit.utils.ParameterDriversList;
@@ -70,6 +74,9 @@ public abstract class AbstractPropagatorBuilder implements PropagatorBuilder {
     /** Position scale to use for the orbital drivers. */
     private final double positionScale;
 
+    /** Additional equations. */
+    protected List<AdditionalEquations> additionalEquations;
+
     /** Build a new instance.
      * <p>
      * The template orbit is used as a model to {@link
@@ -110,6 +117,8 @@ public abstract class AbstractPropagatorBuilder implements PropagatorBuilder {
             driver.setSelected(true);
         }
 
+        this.additionalEquations  = new ArrayList<AdditionalEquations>();
+
         if (addDriverForCentralAttraction) {
             final ParameterDriver muDriver = new ParameterDriver(NewtonianAttraction.CENTRAL_ATTRACTION_COEFFICIENT,
                                                                  mu, MU_SCALE, 0, Double.POSITIVE_INFINITY);
@@ -293,4 +302,15 @@ public abstract class AbstractPropagatorBuilder implements PropagatorBuilder {
         // Change the initial orbit date in the builder
         this.initialOrbitDate = newOrbit.getDate();
     }
+
+    /** Add a set of user-specified equations to be integrated along with the orbit propagation.
+     * @param additional additional equations
+     * @author Shiva Iyer
+     * @since 10.1
+     */
+    public void addAdditionalEquations(final AdditionalEquations additional) {
+
+        additionalEquations.add(additional);
+
+    }
 }

src/main/java/org/orekit/propagation/conversion/DSSTPropagatorBuilder.java

@@ -34,6 +34,7 @@ import org.orekit.orbits.PositionAngle;
 import org.orekit.propagation.PropagationType;
 import org.orekit.propagation.Propagator;
 import org.orekit.propagation.SpacecraftState;
+import org.orekit.propagation.integration.AdditionalEquations;
 import org.orekit.propagation.semianalytical.dsst.DSSTPropagator;
 import org.orekit.propagation.semianalytical.dsst.forces.DSSTForceModel;
 import org.orekit.propagation.semianalytical.dsst.forces.DSSTNewtonianAttraction;
@@ -213,6 +214,11 @@ public class DSSTPropagatorBuilder extends AbstractPropagatorBuilder implements
 
         propagator.setInitialState(state, stateType);
 
+	// Add additional equations to the propagator
+	for (AdditionalEquations equation: additionalEquations) {
+	    propagator.addAdditionalEquations(equation);
+	}
+
         return propagator;
     }
 

src/main/java/org/orekit/propagation/conversion/NumericalPropagatorBuilder.java

@@ -33,6 +33,7 @@ import org.orekit.orbits.Orbit;
 import org.orekit.orbits.PositionAngle;
 import org.orekit.propagation.Propagator;
 import org.orekit.propagation.SpacecraftState;
+import org.orekit.propagation.integration.AdditionalEquations;
 import org.orekit.propagation.numerical.NumericalPropagator;
 import org.orekit.utils.ParameterDriver;
 import org.orekit.utils.ParameterDriversList;
@@ -206,6 +207,11 @@ public class NumericalPropagatorBuilder extends AbstractPropagatorBuilder implem
 
         propagator.resetInitialState(state);
 
+	// Add additional equations to the propagator
+	for (AdditionalEquations equation: additionalEquations) {
+	    propagator.addAdditionalEquations(equation);
+	}
+
         return propagator;
     }
 

src/test/java/org/orekit/propagation/conversion/DSSTPropagatorBuilderTest.java

@@ -29,6 +29,8 @@ import org.junit.Before;
 import org.junit.Test;
 import org.orekit.Utils;
 import org.orekit.bodies.CelestialBodyFactory;
+import org.orekit.errors.OrekitException;
+import org.orekit.errors.OrekitMessages;
 import org.orekit.frames.Frame;
 import org.orekit.frames.FramesFactory;
 import org.orekit.orbits.EquinoctialOrbit;
@@ -37,6 +39,7 @@ import org.orekit.orbits.OrbitType;
 import org.orekit.orbits.PositionAngle;
 import org.orekit.propagation.PropagationType;
 import org.orekit.propagation.SpacecraftState;
+import org.orekit.propagation.integration.AdditionalEquations;
 import org.orekit.propagation.numerical.NumericalPropagator;
 import org.orekit.propagation.semianalytical.dsst.DSSTPropagator;
 import org.orekit.propagation.semianalytical.dsst.forces.DSSTForceModel;
@@ -201,6 +204,53 @@ public class DSSTPropagatorBuilderTest {
         assertTrue(hasNewtonianAttraction(builder.getAllForceModels()));
     }
 
+    @Test
+    public void testAdditionalEquations() {
+        // Integrator builder
+        final ODEIntegratorBuilder dp54Builder = new DormandPrince54IntegratorBuilder(minStep, maxStep, dP);
+        // Propagator builder
+        final DSSTPropagatorBuilder builder = new DSSTPropagatorBuilder(orbit,
+                                                                  dp54Builder,
+                                                                  1.0,
+                                                                  PropagationType.MEAN,
+                                                                  PropagationType.MEAN);
+        builder.addForceModel(moon);
+        builder.addForceModel(sun);
+
+	// Add additional equations
+        builder.addAdditionalEquations(new AdditionalEquations() {
+
+            public String getName() {
+                return "linear";
+            }
+
+            public double[] computeDerivatives(SpacecraftState s, double[] pDot) {
+                pDot[0] = 1.0;
+                return new double[7];
+            }
+        });
+
+	builder.addAdditionalEquations(new AdditionalEquations() {
+
+	    public String getName() {
+		return "linear";
+	    }
+
+	    public double[] computeDerivatives(SpacecraftState s, double[] pDot) {
+		pDot[0] = 1.0;
+		return new double[7];
+	    }
+	});
+
+        try {
+	    // Build the propagator
+	    builder.buildPropagator(builder.getSelectedNormalizedParameters());
+            Assert.fail("an exception should have been thrown");
+        } catch (OrekitException oe) {
+            Assert.assertEquals(oe.getSpecifier(), OrekitMessages.ADDITIONAL_STATE_NAME_ALREADY_IN_USE);
+        }
+    }
+
     @Before
     public void setUp() throws IOException, ParseException {
         

src/test/java/org/orekit/propagation/conversion/NumericalConverterTest.java

@@ -49,6 +49,7 @@ import org.orekit.orbits.Orbit;
 import org.orekit.orbits.OrbitType;
 import org.orekit.orbits.PositionAngle;
 import org.orekit.propagation.SpacecraftState;
+import org.orekit.propagation.integration.AdditionalEquations;
 import org.orekit.propagation.numerical.NumericalPropagator;
 import org.orekit.time.AbsoluteDate;
 import org.orekit.time.TimeScalesFactory;
@@ -210,6 +211,52 @@ public class NumericalConverterTest {
         checkFit(teBuilder);
     }
 
+    @Test
+    public void testAdditionalEquations() {
+        // Integrator builder
+        final ODEIntegratorBuilder dp54Builder = new DormandPrince54IntegratorBuilder(minStep, maxStep, dP);
+        // Propagator builder
+        final NumericalPropagatorBuilder builder =
+                        new NumericalPropagatorBuilder(OrbitType.CIRCULAR.convertType(orbit),
+                                                       dp54Builder,
+                                                       PositionAngle.TRUE, 1.0);
+        builder.addForceModel(drag);
+        builder.addForceModel(gravity);
+
+	// Add additional equations
+        builder.addAdditionalEquations(new AdditionalEquations() {
+
+            public String getName() {
+                return "linear";
+            }
+
+            public double[] computeDerivatives(SpacecraftState s, double[] pDot) {
+                pDot[0] = 1.0;
+                return new double[7];
+            }
+        });
+
+	builder.addAdditionalEquations(new AdditionalEquations() {
+
+	    public String getName() {
+		return "linear";
+	    }
+
+	    public double[] computeDerivatives(SpacecraftState s, double[] pDot) {
+		pDot[0] = 1.0;
+		return new double[7];
+	    }
+	});
+
+        try {
+	    // Build the numerical propagator
+	    builder.buildPropagator(builder.getSelectedNormalizedParameters());
+            Assert.fail("an exception should have been thrown");
+        } catch (OrekitException oe) {
+            Assert.assertEquals(oe.getSpecifier(), OrekitMessages.ADDITIONAL_STATE_NAME_ALREADY_IN_USE);
+        }
+    }
+
     protected void checkFit(final Orbit orbit, final double duration,
                             final double stepSize, final double threshold,
                             final double expectedRMS,