/* Copyright 2002-2017 CS Systèmes d'Information
 * Licensed to CS Systèmes d'Information (CS) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * CS licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *   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,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
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
 */
interface TLEConstants {

    /** Constant 1.0 / 3.0. */
    double ONE_THIRD = 1.0 / 3.0;

    /** Constant 2.0 / 3.0. */
    double TWO_THIRD = 2.0 / 3.0;

    /** Earth radius in km. */
    double EARTH_RADIUS = 6378.135;

    /** Equatorial radius rescaled (1.0). */
    double NORMALIZED_EQUATORIAL_RADIUS = 1.0;

    /** Time units per julian day. */
    double MINUTES_PER_DAY = 1440.0;

    // CHECKSTYLE: stop JavadocVariable check
    // Potential perturbation coefficients
    double XKE    = 0.0743669161331734132; // mu = 3.986008e+14;
    double XJ3    = -2.53881e-6;
    double XJ2    = 1.082616e-3;
    double XJ4    = -1.65597e-6;
    double CK2    = 0.5 * XJ2 * NORMALIZED_EQUATORIAL_RADIUS * NORMALIZED_EQUATORIAL_RADIUS;
    double CK4    = -0.375 * XJ4 * NORMALIZED_EQUATORIAL_RADIUS * NORMALIZED_EQUATORIAL_RADIUS *
                    NORMALIZED_EQUATORIAL_RADIUS * NORMALIZED_EQUATORIAL_RADIUS;
    double S      = NORMALIZED_EQUATORIAL_RADIUS * (1. + 78. / EARTH_RADIUS);
    double QOMS2T = 1.880279159015270643865e-9;
    double A3OVK2 = -XJ3 / CK2 * NORMALIZED_EQUATORIAL_RADIUS * NORMALIZED_EQUATORIAL_RADIUS *
                    NORMALIZED_EQUATORIAL_RADIUS;
    // CHECKSTYLE: resume JavadocVariable check

    /** Earth gravity coefficient in m³/s². */
    double MU = XKE * XKE * EARTH_RADIUS * EARTH_RADIUS * EARTH_RADIUS * (1000 * 1000 * 1000) / (60 * 60);

}