1   /* Copyright 2022-2025 Luc Maisonobe
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.propagation.analytical.gnss;
18  
19  import org.hipparchus.analysis.differentiation.Gradient;
20  import org.orekit.propagation.FieldSpacecraftState;
21  import org.orekit.propagation.analytical.AbstractAnalyticalGradientConverter;
22  import org.orekit.utils.ParameterDriver;
23  
24  import java.util.List;
25  
26  /** Converter for GNSS propagator.
27   * @author Luc Maisonobe
28   * @since 13.0
29   */
30  class GnssGradientConverter extends AbstractAnalyticalGradientConverter {
31  
32      /** Fixed dimension of the state. */
33      public static final int FREE_STATE_PARAMETERS = 6;
34  
35      /** Orbit propagator. */
36      private final GNSSPropagator propagator;
37  
38      /** Simple constructor.
39       * @param propagator orbit propagator used to access initial orbit
40       */
41      GnssGradientConverter(final GNSSPropagator propagator) {
42          super(propagator, FREE_STATE_PARAMETERS);
43          this.propagator = propagator;
44      }
45  
46      /** {@inheritDoc} */
47      @Override
48      public FieldGnssPropagator<Gradient> getPropagator() {
49  
50          // prepare initial state with proper derivatives
51          final FieldSpacecraftState<Gradient> state = getState(this);
52  
53          // build propagator handling gradient
54          return new FieldGnssPropagator<>(state,
55                                           propagator.getOrbitalElements().toField(state.getDate().getField()),
56                                           propagator.getECEF(), propagator.getAttitudeProvider(),
57                                           state.getMass());
58  
59      }
60  
61      /** {@inheritDoc} */
62      @Override
63      public List<ParameterDriver> getParametersDrivers() {
64          return propagator.getOrbitalElements().getParametersDrivers();
65      }
66  
67  }