PlotDetection(viewer, detections, 'ECEF') ĭetectableInput = isDetectable(tracker,time, covcon) % Show 10-sigma covariance ellipses for better visibility % Reset scenario, seed, and globe display The utility function isDetectable calculates which tracks are detectable at each simulation step.Īdditionally, a utility function deleteBadTracks is used to delete divergent tracks faster.
This is important for not penalizing tracks that are propagated outside of the radar surveillance areas. Setting the property HasDetectableTrackIDsInput to true allows the tracker to accept an input that indicates whether a tracked object is detectable in the surveillance region. Call the detect method on the tracking scenario to obtain all the detections in the scene.Ī multi-object tracker trackerJPDA is used to create new tracks, associate detections to existing tracks, estimate their state, and delete divergent tracks. The sensor models use the ground truth to generate synthetic detections. Simulate synthetic detections and track space debris After several orbit periods, all space debris pass through the surveillance beams of the radars. The trajectories are plotted in ECEF coordinates, and therefore the entire trajectory rotates towards the west due to Earth rotation. Most of the generated debris objects are on orbits with high inclination angles close to 80 deg. On the virtual globe, you can see the space debris represented by white dots with individual trailing trajectories shown by white lines. You use trackingGlobeViewer to visualize all the elements defined in the tracking scenario: individual debris objects and their trajectories, radar fans, radar detections, and tracks. Station4.Sensors = radar4 Visualize the ground truth with trackingGlobeViewer % Create fan-shaped monostatic radars to monitor space debris objects Having four dispersed radars allows for the re-detection of space debris to correct their position estimates and also acquiring new debris detections. A pair of stations are located in the Pacific ocean and in the Atlantic ocean, whereas a second pair of surveillance stations are located near the poles. The fans cut through the orbits of debris objects to maximize the number of object detections. In this example, we define four antipodal stations with fan-shaped radar beams looking into space. 'Velocity',data(i).InitialVelocity) %#ok end Model space surveillance radars % integration step 10sec 'Position',data(i).InitialPosition. = oe2rv(range(i),ecc(i),inc(i),lan(i),w(i),nu(i)) ĭata(i).InitialVelocity = v %#ok end % Create platforms and assign them trajectories using the keplerorbit motion model for i=1:numDebrisĭebris(i).Trajectory =. % Convert to initial position and velocity for i = 1:numDebris Then convert these orbital elements to position and velocity vectors by using the supporting function oe2rv. This is done by obtaining the traditional orbital elements (semi-major axis, eccentricity, inclination, longitude of the ascending node, argument of periapsis, and true anomaly angles) of these objects from random distributions. The function keplerorbit provided below uses a 4th order Runge-Kutta numerical integration of this equation to propagate the position and velocity in time.įirst, we create initial positions and velocities for the space debris objects. Where μ is the standard gravitational parameter of the Earth, r → is the ECEF debris object position vector, r is the norm of the position vector, and Ω →is the Earth rotation vector. The ECEF debris object acceleration vector isĪ → = - μ r 3 r → - 2 Ω → × d d t r → - Ω → × ( Ω → × r → ), Since the equation of motion is expressed in ECEF frame which is a non-inertial reference frame, the Coriolis and centripetal forces are accounted for. Higher order effects in Earth gravitational field and environmental disturbances are not accounted for. Trajectories of space objects rotating around the Earth can be approximated with a Keplerian model, which assumes that Earth is a point-mass body and the objects orbiting around the earth have negligible masses. The helperMotionTrajectory class used in this example defines debris object trajectories using a custom motion model function. Platform positions and velocities are defined using Cartesian coordinates in this frame. The Y axis completes the right-handed system. The X axis points towards the intersection of the equator and the Greenwich meridian. The origin of this frame is at the center of the Earth and the Z axis points toward the north pole. You use the Earth-Centered-Earth-Fixed (ECEF) reference frame. Scene = trackingScenario( 'IsEarthCentered',true, 'InitialAdvance', 'UpdateInterval'.
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