astronomia/es/elementequinox.js

var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; };

function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

/**
 * @copyright 2013 Sonia Keys
 * @copyright 2016 commenthol
 * @license MIT
 * @module elementequinox
 */
/**
 * Elementequinox: Chapter 24, Reduction of Ecliptical Elements
 * from one Equinox to another one.
 *
 * See package precess for the method EclipticPrecessor.ReduceElements and
 * associated example.  The method is described in this chapter but located
 * in package precess so that it can be a method of EclipticPrecessor.
 */

import base from './base';

/**
 * Elements are the orbital elements of a solar system object which change
 * from one equinox to another.
 *
 * @param {Number} inc  - inclination
 * @param {Number} node - longitude of ascending node (Ω)
 * @param {Number} peri - argument of perihelion (ω)
 */
export var Elements = function Elements(inc, node, peri) {
  _classCallCheck(this, Elements);

  if ((typeof inc === 'undefined' ? 'undefined' : _typeof(inc)) === 'object') {
    node = inc.pode;
    peri = inc.peri;
    inc = inc.inc;
  }
  this.inc = inc || 0;
  this.node = node || 0;
  this.peri = peri || 0;
};

// (24.4) p. 161
var S = 0.0001139788;
var C = 0.9999999935;
/**
 * ReduceB1950ToJ2000 reduces orbital elements of a solar system body from
 * equinox B1950 to J2000.
 *
 * @param {Elements} eFrom
 * @returns {Elements} eTo
 */
export function reduceB1950ToJ2000(eFrom) {
  var W = eFrom.node - 174.298782 * Math.PI / 180;

  var _base$sincos = base.sincos(eFrom.inc),
      si = _base$sincos[0],
      ci = _base$sincos[1];

  var _base$sincos2 = base.sincos(W),
      sW = _base$sincos2[0],
      cW = _base$sincos2[1];

  var A = si * sW;
  var B = C * si * cW - S * ci;
  var eTo = new Elements();
  eTo.inc = Math.asin(Math.hypot(A, B));
  eTo.node = base.pmod(174.997194 * Math.PI / 180 + Math.atan2(A, B), 2 * Math.PI);
  eTo.peri = base.pmod(eFrom.peri + Math.atan2(-S * sW, C * si - S * ci * cW), 2 * Math.PI);
  return eTo;
}

var Lp = 4.50001688 * Math.PI / 180;
var L = 5.19856209 * Math.PI / 180;
var J = 0.00651966 * Math.PI / 180;

/**
 * ReduceB1950ToJ2000 reduces orbital elements of a solar system body from
 * equinox B1950 in the FK4 system to equinox J2000 in the FK5 system.
 *
 * @param {Elements} eFrom
 * @returns {Elements} eTo
 */
export function reduceB1950FK4ToJ2000FK5(eFrom) {
  var W = L + eFrom.node;

  var _base$sincos3 = base.sincos(eFrom.inc),
      si = _base$sincos3[0],
      ci = _base$sincos3[1];

  var _base$sincos4 = base.sincos(J),
      sJ = _base$sincos4[0],
      cJ = _base$sincos4[1];

  var _base$sincos5 = base.sincos(W),
      sW = _base$sincos5[0],
      cW = _base$sincos5[1];

  var eTo = new Elements();
  eTo.inc = Math.acos(ci * cJ - si * sJ * cW);
  eTo.node = base.pmod(Math.atan2(si * sW, ci * sJ + si * cJ * cW) - Lp, 2 * Math.PI);
  eTo.peri = base.pmod(eFrom.peri + Math.atan2(sJ * sW, si * cJ + ci * sJ * cW), 2 * Math.PI);
  return eTo;
}

export default {
  Elements: Elements,
  reduceB1950ToJ2000: reduceB1950ToJ2000,
  reduceB1950FK4ToJ2000FK5: reduceB1950FK4ToJ2000FK5
};