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17 package org.orekit.estimation.measurements.generation;
18
19 import org.hipparchus.linear.MatrixUtils;
20 import org.hipparchus.linear.RealMatrix;
21 import org.hipparchus.random.CorrelatedRandomVectorGenerator;
22 import org.hipparchus.random.GaussianRandomGenerator;
23 import org.hipparchus.random.RandomGenerator;
24 import org.hipparchus.random.Well19937a;
25 import org.hipparchus.util.FastMath;
26 import org.junit.jupiter.api.Assertions;
27 import org.junit.jupiter.api.BeforeEach;
28 import org.junit.jupiter.api.Test;
29 import org.orekit.estimation.Context;
30 import org.orekit.estimation.EstimationTestUtils;
31 import org.orekit.estimation.Force;
32 import org.orekit.estimation.measurements.BistaticRange;
33 import org.orekit.estimation.measurements.EstimatedMeasurementBase;
34 import org.orekit.estimation.measurements.GroundStation;
35 import org.orekit.estimation.measurements.ObservableSatellite;
36 import org.orekit.estimation.measurements.modifiers.Bias;
37 import org.orekit.orbits.OrbitType;
38 import org.orekit.orbits.PositionAngleType;
39 import org.orekit.propagation.Propagator;
40 import org.orekit.propagation.SpacecraftState;
41 import org.orekit.propagation.conversion.NumericalPropagatorBuilder;
42 import org.orekit.propagation.events.BooleanDetector;
43 import org.orekit.propagation.events.ElevationDetector;
44 import org.orekit.time.AbsoluteDate;
45 import org.orekit.time.FixedStepSelector;
46 import org.orekit.time.TimeScalesFactory;
47
48 import java.util.SortedSet;
49
50 public class BistaticRangeBuilderTest {
51
52 private static final double SIGMA = 10.0;
53 private static final double BIAS = 3.0;
54
55 private MeasurementBuilder<BistaticRange> getBuilder(final RandomGenerator random,
56 final GroundStation emitter,
57 final GroundStation receiver,
58 final ObservableSatellite satellite) {
59 final RealMatrix covariance = MatrixUtils.createRealDiagonalMatrix(new double[] { SIGMA * SIGMA });
60 MeasurementBuilder<BistaticRange> brb =
61 new BistaticRangeBuilder(random == null ? null : new CorrelatedRandomVectorGenerator(covariance,
62 1.0e-10,
63 new GaussianRandomGenerator(random)),
64 emitter, receiver, SIGMA, 1.0, satellite);
65 brb.addModifier(new Bias<>(new String[] { "bias" },
66 new double[] { BIAS },
67 new double[] { 1.0 },
68 new double[] { Double.NEGATIVE_INFINITY },
69 new double[] { Double.POSITIVE_INFINITY }));
70 return brb;
71 }
72
73 @Test
74 public void testForward() {
75 doTest(0xf50c0ce7c8c1dab2L, 0.0, 1.2, 3.2 * SIGMA);
76 }
77
78 @Test
79 public void testBackward() {
80 doTest(0x453a681440d01832L, 0.0, -1.2, 2.9 * SIGMA);
81 }
82
83 private Propagator buildPropagator() {
84 return EstimationTestUtils.createPropagator(context.initialOrbit, propagatorBuilder);
85 }
86
87 private void doTest(long seed, double startPeriod, double endPeriod, double tolerance) {
88 Generator generator = new Generator();
89 final double step = 60.0;
90 final GroundStation emitter = context.BRRstations.getFirst();
91 final GroundStation receiver = context.BRRstations.getSecond();
92 generator.addPropagator(buildPropagator());
93 generator.addPropagator(buildPropagator());
94 ObservableSatellite satellite = generator.addPropagator(buildPropagator());
95 generator.addPropagator(buildPropagator());
96 generator.addScheduler(new EventBasedScheduler<>(getBuilder(new Well19937a(seed), emitter, receiver, satellite),
97 new FixedStepSelector(step, TimeScalesFactory.getUTC()),
98 generator.getPropagator(satellite),
99 BooleanDetector.andCombine(EstimationTestUtils.getElevationDetector(emitter.getBaseFrame(),
100 FastMath.toRadians(5.0)),
101 EstimationTestUtils.getElevationDetector(receiver.getBaseFrame(),
102 FastMath.toRadians(5.0))),
103 SignSemantic.FEASIBLE_MEASUREMENT_WHEN_POSITIVE));
104 final GatheringSubscriber gatherer = new GatheringSubscriber();
105 generator.addSubscriber(gatherer);
106 final double period = context.initialOrbit.getKeplerianPeriod();
107 AbsoluteDate t0 = context.initialOrbit.getDate().shiftedBy(startPeriod * period);
108 AbsoluteDate t1 = context.initialOrbit.getDate().shiftedBy(endPeriod * period);
109 generator.generate(t0, t1);
110 SortedSet<EstimatedMeasurementBase<?>> measurements = gatherer.getGeneratedMeasurements();
111 Propagator propagator = buildPropagator();
112 double maxError = 0;
113 AbsoluteDate previous = null;
114 AbsoluteDate tInf = t0.isBefore(t1) ? t0 : t1;
115 AbsoluteDate tSup = t0.isBefore(t1) ? t1 : t0;
116 for (EstimatedMeasurementBase<?> measurement : measurements) {
117 AbsoluteDate date = measurement.getDate();
118 double[] m = measurement.getObservedValue();
119 Assertions.assertTrue(date.compareTo(tInf) >= 0);
120 Assertions.assertTrue(date.compareTo(tSup) <= 0);
121 if (previous != null) {
122 if (t0.isBefore(t1)) {
123
124 Assertions.assertTrue(date.durationFrom(previous) >= 0.999999 * step);
125 } else {
126
127 Assertions.assertTrue(previous.durationFrom(date) >= 0.999999 * step);
128 }
129 }
130 previous = date;
131 SpacecraftState state = propagator.propagate(date);
132 double[] e = measurement.
133 getObservedMeasurement().
134 estimateWithoutDerivatives(new SpacecraftState[] { state }).
135 getEstimatedValue();
136 for (int i = 0; i < m.length; ++i) {
137 maxError = FastMath.max(maxError, FastMath.abs(e[i] - m[i]));
138 }
139 }
140 Assertions.assertEquals(0.0, maxError, tolerance);
141 }
142
143 @BeforeEach
144 public void setUp() {
145 context = EstimationTestUtils.eccentricContext("regular-data:potential:tides");
146
147 propagatorBuilder = context.createBuilder(OrbitType.KEPLERIAN, PositionAngleType.TRUE, true,
148 1.0e-6, 300.0, 0.001, Force.POTENTIAL,
149 Force.THIRD_BODY_SUN, Force.THIRD_BODY_MOON);
150 }
151
152 Context context;
153 NumericalPropagatorBuilder propagatorBuilder;
154
155 }