earthtrek-core/src/js/earthtrek-propagation.js

Global Nominee NASA Space Apps Challenge 2017 Buenos Aires - Global Finalist (Best Use of Data) NASA Space Apps Challenge 2017 - 1D, 2D, 3D, Go! Challenge

/**
 * @class Satellite Propagation
 * @module EarthTrek
 * @author SATrek
 * @author Alejandro Sanchez <alejandro.sanchez.trek@gmail.com>
 * @description EarthTrek - NASA Space Apps 2017 12 MAY 2017.
 */

var satellite = require('satellite.js');
if (satellite.satellite != undefined) {
    satellite = satellite.satellite;
}
var satellitePropagation = satellitePropagation || {};
/**
 * Propagate Satellite
 * @param string tleLine1
 * @param string tleLine2
 * @param Date date
 * @returns {*}
 */
satellitePropagation.propagate = function(tleLine1, tleLine2, date) {
    var satrec = satellite.twoline2satrec(tleLine1, tleLine2);
    var positionAndVelocity = satellite.propagate(satrec, date);
    return positionAndVelocity;
}

/**
 * Get Velocity in KM
 * @returns {number}
 */
satellitePropagation.getVelocity = function(velocityEci) {
    var vel = Math.sqrt(Math.pow(velocityEci.x, 2) + Math.pow(velocityEci.y, 2) + Math.pow(velocityEci.z, 2));
    return vel;
}

/**
 * Get Position Degree Coordinates (longitude, latitude, height)
 * @param string tleLine1
 * @param string tleLine2
 * @param Date date
 * @returns {*}
 */
satellitePropagation.getPositionAndVelocity = function(tleLine1, tleLine2, date) {
    var positionAndVelocity = this.propagate(tleLine1, tleLine2, date);
    var positionEci = positionAndVelocity.position;

    var gmst = satellite.gstimeFromDate(
        date.getUTCFullYear(),
        date.getUTCMonth() + 1,
        date.getUTCDate(),
        date.getUTCHours(),
        date.getUTCMinutes(),
        date.getUTCSeconds()
    );

    var positionGd  = satellite.eciToGeodetic(positionEci, gmst);
    var longitude = positionGd.longitude,
        latitude  = positionGd.latitude;

    var longitudeStr = satellite.degreesLong(longitude),
        latitudeStr  = satellite.degreesLat(latitude);

    positionGd.longitude = longitudeStr;
    positionGd.latitude = latitudeStr;
    positionGd.height = positionGd.height * 1000;
    return {position: positionGd, velocity: positionAndVelocity.velocity};
}

module.exports = satellitePropagation;