1   /* Copyright 2002-2025 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 java.io.Serializable;
20  
21  /** TAI UTC offset model.
22   * @see UTCTAIOffsetsLoader
23   * @author Luc Maisonobe
24   * @since 7.1
25   */
26  public class OffsetModel implements Serializable {
27  
28      /** Serializable UID. */
29      private static final long serialVersionUID = 20240721L;
30  
31      /** Date of the offset start. */
32      private final DateComponents start;
33  
34      /** Reference date of the linear model as a modified julian day. */
35      private final int mjdRef;
36  
37      /** Offset at reference date in seconds (TAI minus UTC). */
38      private final TimeOffset offset;
39  
40      /** Offset slope in nanoseconds per UTC second (TAI minus UTC / dUTC). */
41      private final int slope;
42  
43      /** Constructor for a linear offset model.
44       * <p>
45       * These models were used prior to 1972.
46       * </p>
47       * @param start date of the offset start
48       * @param mjdRef reference date of the linear model as a modified julian day
49       * @param offset offset at reference date in seconds (TAI minus UTC)
50       * @param slope offset slope in nanoseconds per UTC second (TAI minus UTC / dUTC)
51       */
52      public OffsetModel(final DateComponents start,
53                         final int mjdRef, final TimeOffset offset, final int slope) {
54          this.start  = start;
55          this.mjdRef = mjdRef;
56          this.offset = offset;
57          this.slope  = slope;
58      }
59  
60      /** Constructor for a constant offset model.
61       * <p>
62       * These models are used since 1972.
63       * </p>
64       * @param start date of the offset start
65       * @param offset offset at reference date in seconds (TAI minus UTC)
66       */
67      public OffsetModel(final DateComponents start, final int offset) {
68          this(start, 41317, new TimeOffset(offset, 0L), 0);
69      }
70  
71      /** Get the date of the offset start.
72       * @return date of the offset start
73       */
74      public DateComponents getStart() {
75          return start;
76      }
77  
78      /** Get the reference date of the linear model as a modified julian day.
79       * @return reference date of the linear model as a modified julian day
80       */
81      public int getMJDRef() {
82          return mjdRef;
83      }
84  
85      /** Offset at reference date in seconds (TAI minus UTC).
86       * @return offset at reference date in seconds (TAI minus UTC)
87       */
88      public TimeOffset getOffset() {
89          return offset;
90      }
91  
92      /** Offset slope in nanoseconds per UTC second (TAI minus UTC / dUTC).
93       * @return offset slope in nanoseconds per UTC second  (TAI minus UTC / dUTC)
94       */
95      public int getSlope() {
96          return slope;
97      }
98  
99  }