TLE2ToCZML/node_modules/satellite.js/lib/propagation/initl.js

/*!
 * satellite-js v5.0.0
 * (c) 2013 Shashwat Kandadai and UCSC
 * https://github.com/shashwatak/satellite-js
 * License: MIT
 */

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports["default"] = initl;
var _constants = require("../constants");
var _gstime = _interopRequireDefault(require("./gstime"));
function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { "default": obj }; }
/*-----------------------------------------------------------------------------
 *
 *                           procedure initl
 *
 *  this procedure initializes the sgp4 propagator. all the initialization is
 *    consolidated here instead of having multiple loops inside other routines.
 *
 *  author        : david vallado                  719-573-2600   28 jun 2005
 *
 *  inputs        :
 *    ecco        - eccentricity                           0.0 - 1.0
 *    epoch       - epoch time in days from jan 0, 1950. 0 hr
 *    inclo       - inclination of satellite
 *    no          - mean motion of satellite
 *    satn        - satellite number
 *
 *  outputs       :
 *    ainv        - 1.0 / a
 *    ao          - semi major axis
 *    con41       -
 *    con42       - 1.0 - 5.0 cos(i)
 *    cosio       - cosine of inclination
 *    cosio2      - cosio squared
 *    eccsq       - eccentricity squared
 *    method      - flag for deep space                    'd', 'n'
 *    omeosq      - 1.0 - ecco * ecco
 *    posq        - semi-parameter squared
 *    rp          - radius of perigee
 *    rteosq      - square root of (1.0 - ecco*ecco)
 *    sinio       - sine of inclination
 *    gsto        - gst at time of observation               rad
 *    no          - mean motion of satellite
 *
 *  locals        :
 *    ak          -
 *    d1          -
 *    del         -
 *    adel        -
 *    po          -
 *
 *  coupling      :
 *    getgravconst
 *    gstime      - find greenwich sidereal time from the julian date
 *
 *  references    :
 *    hoots, roehrich, norad spacetrack report #3 1980
 *    hoots, norad spacetrack report #6 1986
 *    hoots, schumacher and glover 2004
 *    vallado, crawford, hujsak, kelso  2006
 ----------------------------------------------------------------------------*/
function initl(options) {
  var ecco = options.ecco,
    epoch = options.epoch,
    inclo = options.inclo,
    opsmode = options.opsmode;
  var no = options.no;

  // sgp4fix use old way of finding gst
  // ----------------------- earth constants ---------------------
  // sgp4fix identify constants and allow alternate values

  // ------------- calculate auxillary epoch quantities ----------
  var eccsq = ecco * ecco;
  var omeosq = 1.0 - eccsq;
  var rteosq = Math.sqrt(omeosq);
  var cosio = Math.cos(inclo);
  var cosio2 = cosio * cosio;

  // ------------------ un-kozai the mean motion -----------------
  var ak = Math.pow(_constants.xke / no, _constants.x2o3);
  var d1 = 0.75 * _constants.j2 * (3.0 * cosio2 - 1.0) / (rteosq * omeosq);
  var delPrime = d1 / (ak * ak);
  var adel = ak * (1.0 - delPrime * delPrime - delPrime * (1.0 / 3.0 + 134.0 * delPrime * delPrime / 81.0));
  delPrime = d1 / (adel * adel);
  no /= 1.0 + delPrime;
  var ao = Math.pow(_constants.xke / no, _constants.x2o3);
  var sinio = Math.sin(inclo);
  var po = ao * omeosq;
  var con42 = 1.0 - 5.0 * cosio2;
  var con41 = -con42 - cosio2 - cosio2;
  var ainv = 1.0 / ao;
  var posq = po * po;
  var rp = ao * (1.0 - ecco);
  var method = 'n';

  //  sgp4fix modern approach to finding sidereal time
  var gsto;
  if (opsmode === 'a') {
    //  sgp4fix use old way of finding gst
    //  count integer number of days from 0 jan 1970
    var ts70 = epoch - 7305.0;
    var ds70 = Math.floor(ts70 + 1.0e-8);
    var tfrac = ts70 - ds70;

    //  find greenwich location at epoch
    var c1 = 1.72027916940703639e-2; // eslint-disable-line no-loss-of-precision
    var thgr70 = 1.7321343856509374; // eslint-disable-line no-loss-of-precision
    var fk5r = 5.07551419432269442e-15; // eslint-disable-line no-loss-of-precision
    var c1p2p = c1 + _constants.twoPi;
    gsto = (thgr70 + c1 * ds70 + c1p2p * tfrac + ts70 * ts70 * fk5r) % _constants.twoPi;
    if (gsto < 0.0) {
      gsto += _constants.twoPi;
    }
  } else {
    gsto = (0, _gstime["default"])(epoch + 2433281.5);
  }
  return {
    no: no,
    method: method,
    ainv: ainv,
    ao: ao,
    con41: con41,
    con42: con42,
    cosio: cosio,
    cosio2: cosio2,
    eccsq: eccsq,
    omeosq: omeosq,
    posq: posq,
    rp: rp,
    rteosq: rteosq,
    sinio: sinio,
    gsto: gsto
  };
}