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    * (the "License"); you may not use this file except in compliance with
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    *
    *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
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   * See the License for the specific language governing permissions and
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  package org.orekit.propagation.analytical.tle;
  
  
  /** Constants necessary to TLE propagation.
   *
   * This constants are used in the WGS-72 model, compliant with NORAD implementations.
   *
   * @author Fabien Maussion
   */
  public class TLEConstants {
  
      /** Constant 1.0 / 3.0. */
      public static final double ONE_THIRD = 1.0 / 3.0;
  
      /** Constant 2.0 / 3.0. */
      public static final double TWO_THIRD = 2.0 / 3.0;
  
      /** Earth radius in km. */
      public static final double EARTH_RADIUS = 6378.135;
  
      /** Equatorial radius rescaled (1.0). */
      public static final double NORMALIZED_EQUATORIAL_RADIUS = 1.0;
  
      /** Time units per julian day. */
      public static final double MINUTES_PER_DAY = 1440.0;
  
      // Potential perturbation coefficients
      /** XKE. */
      public static final double XKE    = 0.0743669161331734132; // mu = 3.986008e+14;
      /** XJ3. */
      public static final double XJ3    = -2.53881e-6;
      /** XJ2. */
      public static final double XJ2    = 1.082616e-3;
      /** XJ4. */
      public static final double XJ4    = -1.65597e-6;
      /** CK2. */
      public static final double CK2    = 0.5 * XJ2 * NORMALIZED_EQUATORIAL_RADIUS * NORMALIZED_EQUATORIAL_RADIUS;
      /** CK4. */
      public static final double CK4    = -0.375 * XJ4 * NORMALIZED_EQUATORIAL_RADIUS * NORMALIZED_EQUATORIAL_RADIUS *
                                          NORMALIZED_EQUATORIAL_RADIUS * NORMALIZED_EQUATORIAL_RADIUS;
      /** S. */
      public static final double S      = NORMALIZED_EQUATORIAL_RADIUS * (1. + 78. / EARTH_RADIUS);
      /** QOMS2T. */
      public static final double QOMS2T = 1.880279159015270643865e-9;
      /** A3OVK2. */
      public static final double A3OVK2 = -XJ3 / CK2 * NORMALIZED_EQUATORIAL_RADIUS * NORMALIZED_EQUATORIAL_RADIUS *
                                          NORMALIZED_EQUATORIAL_RADIUS;
  
      // Deep SDP4 constants
      /** ZNS. */
      public static final double ZNS      = 1.19459E-5;
      /** ZES. */
      public static final double ZES      = 0.01675;
      /** ZNL. */
      public static final double ZNL      = 1.5835218E-4;
      /** ZEL. */
      public static final double ZEL      = 0.05490;
      /** THDT. */
      public static final double THDT     = 4.3752691E-3;
      /** C1SS. */
      public static final double C1SS     =  2.9864797E-6;
      /** C1L. */
      public static final double C1L      = 4.7968065E-7;
  
      /** ROOT22. */
      public static final double ROOT22   = 1.7891679E-6;
      /** ROOT32. */
      public static final double ROOT32   = 3.7393792E-7;
      /** ROOT44. */
      public static final double ROOT44   = 7.3636953E-9;
      /** ROOT52. */
      public static final double ROOT52   = 1.1428639E-7;
      /** ROOT54. */
      public static final double ROOT54   = 2.1765803E-9;
  
      /** Q22. */
      public static final double Q22      =  1.7891679E-6;
      /** Q31. */
      public static final double Q31      =  2.1460748E-6;
      /** Q33. */
      public static final double Q33      =  2.2123015E-7;
  
      /** C_FASX2. */
     public static final double C_FASX2  =  0.99139134268488593;
     /** S_FASX2. */
     public static final double S_FASX2  =  0.13093206501640101;
     /** C_2FASX4. */
     public static final double C_2FASX4 =  0.87051638752972937;
     /** S_2FASX4. */
     public static final double S_2FASX4 = -0.49213943048915526;
     /** C_3FASX6. */
     public static final double C_3FASX6 =  0.43258117585763334;
     /** S_3FASX6. */
     public static final double S_3FASX6 =  0.90159499016666422;
 
     /** C_G22. */
     public static final double C_G22    =  0.87051638752972937;
     /** S_G22. */
     public static final double S_G22    = -0.49213943048915526;
     /** C_G32. */
     public static final double C_G32    =  0.57972190187001149;
     /** S_G32. */
     public static final double S_G32    =  0.81481440616389245;
     /** C_G44. */
     public static final double C_G44    = -0.22866241528815548;
     /** S_G44. */
     public static final double S_G44    =  0.97350577801807991;
     /** C_G52. */
     public static final double C_G52    =  0.49684831179884198;
     /** S_G52. */
     public static final double S_G52    =  0.86783740128127729;
     /** C_G54. */
     public static final double C_G54    = -0.29695209575316894;
     /** S_G54. */
     public static final double S_G54    = -0.95489237761529999;
 
     /** Earth gravity coefficient in m³/s². */
     public static final double MU = XKE * XKE * EARTH_RADIUS * EARTH_RADIUS * EARTH_RADIUS * (1000 * 1000 * 1000) / (60 * 60);
 
     /** Private constructor for a utility class.
      */
     private TLEConstants() {
         // nothin to do
     }
 
 }