1   /* Copyright 2022 Bryan Cazabonne
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    * Bryan Cazabonne 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.propagation.semianalytical.dsst.forces;
18  
19  import org.hipparchus.CalculusFieldElement;
20  
21  /**
22   * Semi-analytical J2-squared model.
23   * <p>
24   * This interface is implemented by models providing J2-squared
25   * second-order terms in equinoctial elements. These terms are
26   * used in the computation of the closed-form J2-squared perturbation
27   * in semi-analytical satellite theory.
28   * </p>
29   * @see ZeisModel
30   * @author Bryan Cazabonne
31   * @since 12.0
32   */
33  public interface J2SquaredModel {
34  
35      /**
36       * Compute the J2-squared second-order terms in equinoctial elements.
37       * @param context model context
38       * @return the J2-squared second-order terms in equinoctial elements.
39       *         Order must follow: [A, K, H, Q, P, M]
40       */
41      double[] computeMeanEquinoctialSecondOrderTerms(DSSTJ2SquaredClosedFormContext context);
42  
43      /**
44       * Compute the J2-squared second-order terms in equinoctial elements.
45       * @param context model context
46       * @param <T> type of the elements
47       * @return the J2-squared second-order terms in equinoctial elements.
48       *         Order must follow: [A, K, H, Q, P, M]
49       */
50      <T extends CalculusFieldElement<T>> T[] computeMeanEquinoctialSecondOrderTerms(FieldDSSTJ2SquaredClosedFormContext<T> context);
51  
52  }