1   /* Copyright 2002-2024 CS GROUP
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.time;
18  
19  import org.hipparchus.CalculusFieldElement;
20  
21  /** Terrestrial Time as defined by IAU(1991) recommendation IV.
22   * <p>Coordinate time at the surface of the Earth. IT is the
23   * successor of Ephemeris Time TE.</p>
24   * <p>By convention, TT = TAI + 32.184 s.</p>
25   * <p>This is intended to be accessed thanks to {@link TimeScales},
26   * so there is no public constructor.</p>
27   * @author Luc Maisonobe
28   * @see AbsoluteDate
29   */
30  public class TTScale implements TimeScale {
31  
32      /** Serializable UID. */
33      private static final long serialVersionUID = 20131209L;
34  
35      /** Offset from TAI. */
36      private static final double OFFSET = 32.184;
37  
38      /** Package private constructor for the factory.
39       */
40      TTScale() {
41      }
42  
43      /** {@inheritDoc} */
44      @Override
45      public double offsetFromTAI(final AbsoluteDate date) {
46          return OFFSET;
47      }
48  
49      /** {@inheritDoc} */
50      @Override
51      public <T extends CalculusFieldElement<T>> T offsetFromTAI(final FieldAbsoluteDate<T> date) {
52          return date.getField().getZero().add(OFFSET);
53      }
54  
55      /** {@inheritDoc} */
56      @Override
57      public double offsetToTAI(final DateComponents date, final TimeComponents time) {
58          return -OFFSET;
59      }
60  
61      /** {@inheritDoc} */
62      public String getName() {
63          return "TT";
64      }
65  
66      /** {@inheritDoc} */
67      public String toString() {
68          return getName();
69      }
70  
71  }