112 lines
2.8 KiB
JavaScript
112 lines
2.8 KiB
JavaScript
'use strict';
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Object.defineProperty(exports, '__esModule', { value: true });
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var base = require('./base.cjs');
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/**
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* @copyright 2013 Sonia Keys
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* @copyright 2016 commenthol
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* @license MIT
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* @module nearparabolic
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*/
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/**
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* Elements holds orbital elements for near-parabolic orbits.
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*/
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class Elements {
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/**
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* @param {Number} timeP - time of Perihelion, T
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* @param {Number} pDis - Perihelion distance, q
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* @param {Number} ecc - eccentricity, e
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*/
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constructor (timeP, pDis, ecc) {
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this.timeP = timeP;
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this.pDis = pDis;
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this.ecc = ecc;
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}
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/**
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* AnomalyDistance returns true anomaly and distance for near-parabolic orbits.
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*
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* True anomaly ν returned in radians. Distance r returned in AU.
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* An error is returned if the algorithm fails to converge.
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*/
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anomalyDistance (jde) {
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// fairly literal translation of code on p. 246
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const q1 = base["default"].K * Math.sqrt((1 + this.ecc) / this.pDis) / (2 * this.pDis); // line 20
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const g = (1 - this.ecc) / (1 + this.ecc); // line 20
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const t = jde - this.timeP; // line 22
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if (t === 0) { // line 24
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return { ano: 0, dist: this.pDis, err: null }
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}
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const d1 = 1e4;
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const d = 1e-9; // line 14
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const q2 = q1 * t; // line 28
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let s = 2.0 / (3 * Math.abs(q2)); // line 30
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s = 2 / Math.tan(2 * Math.atan(Math.cbrt(Math.tan(Math.atan(s) / 2))));
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if (t < 0) { // line 34
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s = -s;
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}
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if (this.ecc !== 1) { // line 36
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let l = 0; // line 38
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for (;;) {
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const s0 = s; // line 40
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let z = 1.0;
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const y = s * s;
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let g1 = -y * s;
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let q3 = q2 + 2 * g * s * y / 3; // line 42
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for (;;) {
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z += 1; // line 44
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g1 = -g1 * g * y; // line 46
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const z1 = (z - (z + 1) * g) / (2 * z + 1); // line 48
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const f = z1 * g1; // line 50
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q3 += f; // line 52
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if (z > 50 || Math.abs(f) > d1) { // line 54
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return {
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err: new Error('No convergence')
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}
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}
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if (Math.abs(f) <= d) { // line 56
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break
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}
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}
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l++; // line 58
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if (l > 50) {
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return {
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err: new Error('No convergence')
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}
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}
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for (;;) {
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const s1 = s; // line 60
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s = (2 * s * s * s / 3 + q3) / (s * s + 1);
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if (Math.abs(s - s1) <= d) { // line 62
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break
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}
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}
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if (Math.abs(s - s0) <= d) { // line 64
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break
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}
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}
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}
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let ν = 2 * Math.atan(s); // line 66
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const r = this.pDis * (1 + this.ecc) / (1 + this.ecc * Math.cos(ν)); // line 68
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if (ν < 0) { // line 70
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ν += 2 * Math.PI;
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}
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return {
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ano: ν,
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dist: r,
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err: null
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}
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}
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}
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var nearparabolic = {
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Elements
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};
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exports.Elements = Elements;
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exports["default"] = nearparabolic;
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