1   /* Copyright 2002-2023 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  /** Galileo system time scale.
22   * <p>By convention, TGST = UTC + 13s at Galileo epoch (1999-08-22T00:00:00Z).</p>
23   * <p>This is intended to be accessed thanks to {@link TimeScales},
24   * so there is no public constructor.</p>
25   * <p>
26   * Galileo System Time and GPS time are very close scales. Without any errors, they
27   * should be identical. The offset between these two scales is the GGTO, it depends
28   * on the clocks used to realize the time scales. It is of the order of a few
29   * tens nanoseconds. This class does not implement this offset, so it is virtually
30   * identical to the {@link GPSScale GPS scale}.
31   * </p>
32   * @author Luc Maisonobe
33   * @see AbsoluteDate
34   */
35  public class GalileoScale implements TimeScale {
36  
37      /** Serializable UID. */
38      private static final long serialVersionUID = 20131209L;
39  
40      /** Offset from TAI. */
41      private static final double OFFSET = -19;
42  
43      /** Package private constructor for the factory.
44       */
45      GalileoScale() {
46      }
47  
48      /** {@inheritDoc} */
49      @Override
50      public double offsetFromTAI(final AbsoluteDate date) {
51          return OFFSET;
52      }
53  
54      /** {@inheritDoc} */
55      @Override
56      public <T extends CalculusFieldElement<T>> T offsetFromTAI(final FieldAbsoluteDate<T> date) {
57          return date.getField().getZero().add(OFFSET);
58      }
59  
60      /** {@inheritDoc} */
61      @Override
62      public double offsetToTAI(final DateComponents date, final TimeComponents time) {
63          return -OFFSET;
64      }
65  
66      /** {@inheritDoc} */
67      public String getName() {
68          return "GST";
69      }
70  
71      /** {@inheritDoc} */
72      public String toString() {
73          return getName();
74      }
75  
76  }