1   /* Copyright 2002-2026 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.Serial;
20  import java.io.Serializable;
21  
22  /** TAI UTC offset model.
23   * @see UTCTAIOffsetsLoader
24   * @author Luc Maisonobe
25   * @since 7.1
26   */
27  public class OffsetModel implements Serializable {
28  
29      /** Serializable UID. */
30      @Serial
31      private static final long serialVersionUID = 20240721L;
32  
33      /** Date of the offset start. */
34      private final DateComponents start;
35  
36      /** Reference date of the linear model as a modified julian day. */
37      private final int mjdRef;
38  
39      /** Offset at reference date in seconds (TAI minus UTC). */
40      private final TimeOffset offset;
41  
42      /** Offset slope in nanoseconds per UTC second (TAI minus UTC / dUTC). */
43      private final int slope;
44  
45      /** Constructor for a linear offset model.
46       * <p>
47       * These models were used prior to 1972.
48       * </p>
49       * @param start date of the offset start
50       * @param mjdRef reference date of the linear model as a modified julian day
51       * @param offset offset at reference date in seconds (TAI minus UTC)
52       * @param slope offset slope in nanoseconds per UTC second (TAI minus UTC / dUTC)
53       */
54      public OffsetModel(final DateComponents start,
55                         final int mjdRef, final TimeOffset offset, final int slope) {
56          this.start  = start;
57          this.mjdRef = mjdRef;
58          this.offset = offset;
59          this.slope  = slope;
60      }
61  
62      /** Constructor for a constant offset model.
63       * <p>
64       * These models are used since 1972.
65       * </p>
66       * @param start date of the offset start
67       * @param offset offset at reference date in seconds (TAI minus UTC)
68       */
69      public OffsetModel(final DateComponents start, final int offset) {
70          this(start, 41317, new TimeOffset(offset, 0L), 0);
71      }
72  
73      /** Get the date of the offset start.
74       * @return date of the offset start
75       */
76      public DateComponents getStart() {
77          return start;
78      }
79  
80      /** Get the reference date of the linear model as a modified julian day.
81       * @return reference date of the linear model as a modified julian day
82       */
83      public int getMJDRef() {
84          return mjdRef;
85      }
86  
87      /** Offset at reference date in seconds (TAI minus UTC).
88       * @return offset at reference date in seconds (TAI minus UTC)
89       */
90      public TimeOffset getOffset() {
91          return offset;
92      }
93  
94      /** Offset slope in nanoseconds per UTC second (TAI minus UTC / dUTC).
95       * @return offset slope in nanoseconds per UTC second  (TAI minus UTC / dUTC)
96       */
97      public int getSlope() {
98          return slope;
99      }
100 
101 }