1   /* Copyright 2002-2013 CS Systèmes d'Information
2    * Licensed to CS Systèmes d'Information (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.propagation.sampling;
18  
19  import org.orekit.errors.OrekitException;
20  import org.orekit.errors.PropagationException;
21  import org.orekit.propagation.SpacecraftState;
22  import org.orekit.time.AbsoluteDate;
23  
24  /** This interface is a space-dynamics aware step interpolator.
25   *
26   * <p>It mirrors the <code>StepInterpolator</code> interface from <a
27   * href="http://commons.apache.org/math/"> commons-math</a> but
28   * provides a space-dynamics interface to the methods.</p>
29   * @author Luc Maisonobe
30   */
31  public interface OrekitStepInterpolator {
32  
33      /** Get the current grid date.
34       * @return current grid date
35       */
36      AbsoluteDate getCurrentDate();
37  
38      /** Get the previous grid date.
39       * @return previous grid date
40       */
41      AbsoluteDate getPreviousDate();
42  
43      /** Get the interpolated date.
44       * <p>If {@link #setInterpolatedDate(AbsoluteDate) setInterpolatedDate}
45       * has not been called, the date returned is the same as  {@link
46       * #getCurrentDate() getCurrentDate}.</p>
47       * @return interpolated date
48       * @see #setInterpolatedDate(AbsoluteDate)
49       * @see #getInterpolatedState()
50       */
51      AbsoluteDate getInterpolatedDate();
52  
53      /** Set the interpolated date.
54       * <p>It is possible to set the interpolation date outside of the current
55       * step range, but accuracy will decrease as date is farther.</p>
56       * @param date interpolated date to set
57       * @exception PropagationException if underlying interpolator cannot handle
58       * the date
59       * @see #getInterpolatedDate()
60       * @see #getInterpolatedState()
61       */
62      void setInterpolatedDate(final AbsoluteDate date)
63          throws PropagationException;
64  
65      /** Get the interpolated state.
66       * @return interpolated state at the current interpolation date
67       * @exception OrekitException if state cannot be interpolated or converted
68       * @see #getInterpolatedDate()
69       * @see #setInterpolatedDate(AbsoluteDate)
70       */
71      SpacecraftState getInterpolatedState() throws OrekitException;
72  
73      /** Check is integration direction is forward in date.
74       * @return true if integration is forward in date
75       */
76      boolean isForward();
77  
78  }