astronomia/es/solarxyz.js

/**
 * @copyright 2013 Sonia Keys
 * @copyright 2016 commenthol
 * @license MIT
 * @module solarxyz
 */
/**
 * Solarxyz: Chapter 26, Rectangular Coordinates of the Sun.
 */
import base from './base';
import nutation from './nutation';
import solar from './solar';

/**
 * Position returns rectangular coordinates referenced to the mean equinox of date.
 * @param {planetposition.Planet} earth - VSOP87Planet Earth
 * @param {Number} jde - Julian ephemeris day
 * @return {object} rectangular coordinates
 *   {Number} x
 *   {Number} y
 *   {Number} z
 */
export function position(earth, jde) {
  // (e *pp.V87Planet, jde float64)  (x, y, z float64)
  // (26.1) p. 171
  var _solar$trueVSOP = solar.trueVSOP87(earth, jde),
      lon = _solar$trueVSOP.lon,
      lat = _solar$trueVSOP.lat,
      range = _solar$trueVSOP.range;

  var _base$sincos = base.sincos(nutation.meanObliquity(jde)),
      sε = _base$sincos[0],
      cε = _base$sincos[1];

  var _base$sincos2 = base.sincos(lon),
      ss = _base$sincos2[0],
      cs = _base$sincos2[1];

  var sβ = Math.sin(lat);
  var x = range * cs;
  var y = range * (ss * cε - sβ * sε);
  var z = range * (ss * sε + sβ * cε);
  return { x: x, y: y, z: z };
}

/**
 * LongitudeJ2000 returns geometric longitude referenced to equinox J2000.
 * @param {planetposition.Planet} earth - VSOP87Planet Earth
 * @param {Number} jde - Julian ephemeris day
 * @return {Number} geometric longitude referenced to equinox J2000.
 */
export function longitudeJ2000(earth, jde) {
  var lon = earth.position2000(jde).lon;
  return base.pmod(lon + Math.PI - 0.09033 / 3600 * Math.PI / 180, 2 * Math.PI);
}

/**
 * PositionJ2000 returns rectangular coordinates referenced to equinox J2000.
 * @param {planetposition.Planet} earth - VSOP87Planet Earth
 * @param {Number} jde - Julian ephemeris day
 * @return {object} rectangular coordinates
 *   {Number} x
 *   {Number} y
 *   {Number} z
 */
export function positionJ2000(earth, jde) {
  var _xyz = xyz(earth, jde),
      x = _xyz.x,
      y = _xyz.y,
      z = _xyz.z;
  // (26.3) p. 174


  return {
    x: x + 0.00000044036 * y - 0.000000190919 * z,
    y: -0.000000479966 * x + 0.917482137087 * y - 0.397776982902 * z,
    z: 0.397776982902 * y + 0.917482137087 * z
  };
}

export function xyz(earth, jde) {
  var _earth$position = earth.position2000(jde),
      lon = _earth$position.lon,
      lat = _earth$position.lat,
      range = _earth$position.range;

  var s = lon + Math.PI;
  var β = -lat;

  var _base$sincos3 = base.sincos(s),
      ss = _base$sincos3[0],
      cs = _base$sincos3[1];

  var _base$sincos4 = base.sincos(β),
      sβ = _base$sincos4[0],
      cβ = _base$sincos4[1];
  // (26.2) p. 172


  var x = range * cβ * cs;
  var y = range * cβ * ss;
  var z = range * sβ;
  return { x: x, y: y, z: z };
}

/**
 * PositionB1950 returns rectangular coordinates referenced to B1950.
 *
 * Results are referenced to the mean equator and equinox of the epoch B1950
 * in the FK5 system, not FK4.
 *
 * @param {planetposition.Planet} earth - VSOP87Planet Earth
 * @param {Number} jde - Julian ephemeris day
 * @return {object} rectangular coordinates
 *   {Number} x
 *   {Number} y
 *   {Number} z
 */
export function positionB1950(earth, jde) {
  // (e *pp.V87Planet, jde float64)  (x, y, z float64)
  var _xyz2 = xyz(earth, jde),
      x = _xyz2.x,
      y = _xyz2.y,
      z = _xyz2.z;

  return {
    x: 0.999925702634 * x + 0.012189716217 * y + 0.000011134016 * z,
    y: -0.011179418036 * x + 0.917413998946 * y - 0.397777041885 * z,
    z: -0.004859003787 * x + 0.397747363646 * y + 0.917482111428 * z
  };
}

var ζt = [2306.2181, 0.30188, 0.017998];
var zt = [2306.2181, 1.09468, 0.018203];
var θt = [2004.3109, -0.42665, -0.041833];

/**
 * PositionEquinox returns rectangular coordinates referenced to an arbitrary epoch.
 *
 * Position will be computed for given Julian day "jde" but referenced to mean
 * equinox "epoch" (year).
 *
 * @param {planetposition.Planet} earth - VSOP87Planet Earth
 * @param {Number} jde - Julian ephemeris day
 * @param {Number} epoch
 * @return {object} rectangular coordinates
 *   {Number} x
 *   {Number} y
 *   {Number} z
 */
export function positionEquinox(earth, jde, epoch) {
  var xyz = positionJ2000(earth, jde);
  var x0 = xyz.x;
  var y0 = xyz.y;
  var z0 = xyz.z;
  var t = (epoch - 2000) * 0.01;
  var ζ = base.horner(t, ζt) * t * Math.PI / 180 / 3600;
  var z = base.horner(t, zt) * t * Math.PI / 180 / 3600;
  var θ = base.horner(t, θt) * t * Math.PI / 180 / 3600;

  var _base$sincos5 = base.sincos(ζ),
      sζ = _base$sincos5[0],
      cζ = _base$sincos5[1];

  var _base$sincos6 = base.sincos(z),
      sz = _base$sincos6[0],
      cz = _base$sincos6[1];

  var _base$sincos7 = base.sincos(θ),
      sθ = _base$sincos7[0],
      cθ = _base$sincos7[1];

  var xx = cζ * cz * cθ - sζ * sz;
  var xy = sζ * cz + cζ * sz * cθ;
  var xz = cζ * sθ;
  var yx = -cζ * sz - sζ * cz * cθ;
  var yy = cζ * cz - sζ * sz * cθ;
  var yz = -sζ * sθ;
  var zx = -cz * sθ;
  var zy = -sz * sθ;
  var zz = cθ;
  return {
    x: xx * x0 + yx * y0 + zx * z0,
    y: xy * x0 + yy * y0 + zy * z0,
    z: xz * x0 + yz * y0 + zz * z0
  };
}

export default {
  position: position,
  longitudeJ2000: longitudeJ2000,
  positionJ2000: positionJ2000,
  xyz: xyz,
  positionB1950: positionB1950,
  positionEquinox: positionEquinox
};