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Finder for sub-satellite point eclipse related events #26

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9e384b2
Finder for sub-satellite point eclipse related events
Oct 6, 2020
8a6508d
The inertial frame is extracted from SpacecraftState.
Oct 7, 2020
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71 changes: 61 additions & 10 deletions src/main/java/org/orekit/propagation/events/EclipseDetector.java
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Original file line number Diff line number Diff line change
Expand Up @@ -19,7 +19,10 @@
import org.hipparchus.geometry.euclidean.threed.Vector3D;
import org.hipparchus.ode.events.Action;
import org.hipparchus.util.FastMath;
import org.orekit.bodies.GeodeticPoint;
import org.orekit.bodies.OneAxisEllipsoid;
import org.orekit.frames.Frame;
import org.orekit.frames.FramesFactory;
import org.orekit.propagation.SpacecraftState;
import org.orekit.propagation.events.handlers.EventHandler;
import org.orekit.propagation.events.handlers.StopOnIncreasing;
Expand Down Expand Up @@ -61,6 +64,9 @@ public class EclipseDetector extends AbstractDetector<EclipseDetector> {

/** Umbra, if true, or penumbra, if false, detection flag. */
private final boolean totalEclipse;

/** Sub-satellite point, if true, or Spacecraft, if false, detection flag. */
private final boolean subSatellitePoint;

/** Build a new eclipse detector.
* <p>The new instance is a total eclipse (umbra) detector with default
Expand All @@ -75,7 +81,7 @@ public EclipseDetector(final PVCoordinatesProvider occulted, final double occul
final OneAxisEllipsoid occulting) {
this(DEFAULT_MAXCHECK, DEFAULT_THRESHOLD, DEFAULT_MAX_ITER,
new StopOnIncreasing<EclipseDetector>(),
occulted, occultedRadius, occulting, true);
occulted, occultedRadius, occulting, true, false);
}

/** Private constructor with full parameters.
Expand All @@ -92,29 +98,32 @@ public EclipseDetector(final PVCoordinatesProvider occulted, final double occul
* @param occultedRadius the radius of the body to be occulted in meters
* @param occulting the occulting body
* @param totalEclipse umbra (true) or penumbra (false) detection flag
* @param subSatellitePoint Sub-satellite point (true) or Spacecraft (false) flag
* @since 10.0
*/
private EclipseDetector(final double maxCheck, final double threshold,
final int maxIter, final EventHandler<? super EclipseDetector> handler,
final PVCoordinatesProvider occulted, final double occultedRadius,
final OneAxisEllipsoid occulting, final boolean totalEclipse) {
final OneAxisEllipsoid occulting, final boolean totalEclipse, final boolean subSatellitePoint) {
super(maxCheck, threshold, maxIter, handler);
this.occulted = occulted;
this.occultedRadius = FastMath.abs(occultedRadius);
this.occulting = occulting;
this.totalEclipse = totalEclipse;
this.subSatellitePoint = subSatellitePoint;

}

/** {@inheritDoc} */
@Override
protected EclipseDetector create(final double newMaxCheck, final double newThreshold,
final int nawMaxIter, final EventHandler<? super EclipseDetector> newHandler) {
return new EclipseDetector(newMaxCheck, newThreshold, nawMaxIter, newHandler,
occulted, occultedRadius, occulting, totalEclipse);
occulted, occultedRadius, occulting, totalEclipse, subSatellitePoint);
}

/**
* Setup the detector to full umbra detection.
* Setup the detector to full umbra detection for the satellite.
* <p>
* This will override a penumbra/umbra flag if it has been configured previously.
* </p>
Expand All @@ -124,21 +133,47 @@ protected EclipseDetector create(final double newMaxCheck, final double newThres
*/
public EclipseDetector withUmbra() {
return new EclipseDetector(getMaxCheckInterval(), getThreshold(), getMaxIterationCount(), getHandler(),
occulted, occultedRadius, occulting, true);
occulted, occultedRadius, occulting, true, false);
}

/**
* Setup the detector to penumbra detection.
* Setup the detector to full umbra detection for the sub-satellite point.
* <p>
* This will override a penumbra/umbra flag if it has been configured previously.
* </p>
* @return a new detector with updated configuration (the instance is not changed)
* @see #withUmbra()
* @see #withPenumbra()
* @since 6.1
*/
public EclipseDetector UmbraWithSSP() {
return new EclipseDetector(getMaxCheckInterval(), getThreshold(), getMaxIterationCount(), getHandler(),
occulted, occultedRadius, occulting, true, true);
}

/**
* Setup the detector to penumbra detection for the satellite.
* <p>
* This will override a penumbra/umbra flag if it has been configured previously.
* </p>
* @return a new detector with updated configuration (the instance is not changed)
* @see #penumbraWithSSP()
*/
public EclipseDetector withPenumbra() {
return new EclipseDetector(getMaxCheckInterval(), getThreshold(), getMaxIterationCount(), getHandler(),
occulted, occultedRadius, occulting, false);
occulted, occultedRadius, occulting, false, false);
}

/**
* Setup the detector to penumbra detection for the sub-satellite point.
* <p>
* This will override a penumbra/umbra flag if it has been configured previously.
* </p>
* @return a new detector with updated configuration (the instance is not changed)
* @see #UmbraWithSSP()
*/
public EclipseDetector penumbraWithSSP() {
return new EclipseDetector(getMaxCheckInterval(), getThreshold(), getMaxIterationCount(), getHandler(),
occulted, occultedRadius, occulting, false, true);
}

/** Getter for the occulting body.
Expand Down Expand Up @@ -169,6 +204,14 @@ public double getOccultedRadius() {
public boolean getTotalEclipse() {
return totalEclipse;
}

/** Get the sub-satellite point flag.
* @return the sub-satellite point flag (true for sub-satellite point,
* false for satellite)
*/
public boolean getSubSatellitePoint() {
return subSatellitePoint;
}

/** Compute the value of the switching function.
* This function becomes negative when entering the region of shadow
Expand All @@ -178,7 +221,15 @@ public boolean getTotalEclipse() {
*/
public double g(final SpacecraftState s) {
final Vector3D pted = occulted.getPVCoordinates(s.getDate(), occulting.getBodyFrame()).getPosition();
final Vector3D psat = s.getPVCoordinates(occulting.getBodyFrame()).getPosition();
Vector3D psat = null;
if (subSatellitePoint) {
Frame inertialFrame = FramesFactory.getEME2000();
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The inertial frame should be extracted from SpacecraftState rather than hard-coded to EME2000.
Otherwise, the s.getPVCoordinates().getPosition() in the following line will be inconsistent.

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I fixed it.

GeodeticPoint gp = getOcculting().transform(s.getPVCoordinates().getPosition(), inertialFrame, s.getDate());
GeodeticPoint gpSSP = new GeodeticPoint(gp.getLatitude(), gp.getLongitude(), 1);
psat = getOcculting().transform(gpSSP);
} else {
psat = s.getPVCoordinates(occulting.getBodyFrame()).getPosition();
}
final Vector3D plimb = occulting.pointOnLimb(psat, pted);
final Vector3D ps = psat.subtract(pted);
final Vector3D pi = psat.subtract(plimb);
Expand Down