1 /* Contributed in the public domain.
2 * Licensed to CS GROUP (CS) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * CS licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.orekit.frames;
18
19 import org.hipparchus.CalculusFieldElement;
20 import org.hipparchus.geometry.euclidean.threed.FieldRotation;
21 import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
22 import org.hipparchus.geometry.euclidean.threed.Rotation;
23 import org.hipparchus.geometry.euclidean.threed.RotationConvention;
24 import org.hipparchus.geometry.euclidean.threed.Vector3D;
25 import org.orekit.annotation.DefaultDataContext;
26 import org.orekit.data.DataContext;
27 import org.orekit.time.AbsoluteDate;
28 import org.orekit.time.FieldAbsoluteDate;
29 import org.orekit.time.TimeScalarFunction;
30 import org.orekit.time.TimeScales;
31 import org.orekit.utils.IERSConventions;
32
33 /**
34 * An inertial frame aligned with the ecliptic.
35 * <p>
36 * The IAU defines the ecliptic as "the plane perpendicular to the mean heliocentric
37 * orbital angular momentum vector of the Earth-Moon barycentre in the BCRS (IAU 2006
38 * Resolution B1)." The +z axis is aligned with the angular momentum vector, and the +x
39 * axis is aligned with +x axis of {@link Frames#getMOD(IERSConventions) MOD}.
40 * </p>
41 *
42 * <p>
43 * This implementation agrees with the JPL 406 ephemerides to within 0.5 arc seconds.
44 * </p>
45 *
46 * @since 7.0
47 */
48 public class EclipticProvider implements TransformProvider {
49
50 /** the obliquity of the ecliptic, in radians as a function of time. */
51 private final TimeScalarFunction obliquity;
52
53 /**
54 * Create a transform provider from MOD to an ecliptically aligned frame.
55 *
56 * <p>This constructor uses the {@link DataContext#getDefault() default data context}.
57 *
58 * @param conventions IERS conventions
59 * @see #EclipticProvider(IERSConventions, TimeScales)
60 */
61 @DefaultDataContext
62 public EclipticProvider(final IERSConventions conventions) {
63 this(conventions, DataContext.getDefault().getTimeScales());
64 }
65
66 /**
67 * Create a transform provider from MOD to an ecliptically aligned frame.
68 * @param conventions IERS conventions
69 * @param timeScales to use in computing the transformation.
70 * @since 10.1
71 */
72 public EclipticProvider(final IERSConventions conventions,
73 final TimeScales timeScales) {
74 this.obliquity = conventions.getMeanObliquityFunction(timeScales);
75 }
76
77 @Override
78 public Transform getTransform(final AbsoluteDate date) {
79 //mean obliquity of date
80 final double epsA = obliquity.value(date);
81 return new Transform(date, new Rotation(Vector3D.MINUS_I, epsA, RotationConvention.VECTOR_OPERATOR));
82 }
83
84 @Override
85 public <T extends CalculusFieldElement<T>> FieldTransform<T> getTransform(final FieldAbsoluteDate<T> date) {
86 //mean obliquity of date
87 final T epsA = obliquity.value(date);
88 return new FieldTransform<>(date, new FieldRotation<>(FieldVector3D.getMinusI(date.getField()),
89 epsA,
90 RotationConvention.VECTOR_OPERATOR));
91 }
92
93 }