JsPredict

A Javascript port of the popular predict satellite tracking library.

Based on:

• PREDICT: http://www.qsl.net/kd2bd/predict.html
• PyPredict: https://github.com/nsat/pypredict
• Python-SGP4: https://github.com/brandon-rhodes/python-sgp4

Depends on:

• Satellite.js: https://github.com/shashwatak/satellite-js
• Moment.js: https://github.com/moment/moment

Installation

JsPredict has been pushed to the NPM, Meteor (Atmosphere), and Bower package registries, and can also be used by including the src file directly.

NPM

npm install jspredict

Meteor

meteor add rosh93:jspredict

Bower

bower install jspredict

Manual Include

Download and include moment.js: http://momentjs.com/

Include both satellite.js and jspredict.js to get satellite and jspredict available on the global window namespace.

API

Input Types

tle = 3 line string with "\n" character line breaks

qth = 3 element array [latitude (degrees), longitude (degrees), altitude (km)]

time, start, or end = unix timestamp (ms) or date object "new Date()"

Methods

observe(tle 'required', qth 'optional', time 'optional')

observes(tle 'required', qth 'optional', start 'optional', end 'required', interval 'optional')

transits(tle 'required', qth 'required', start 'optional', end 'required', minElevation 'optional', maxTransits 'optional')

Examples

Observe a Satellite:

> var tle = '0 LEMUR-2 JEROEN\n1 40934U 15052E   15306.10048119  .00001740  00000-0  15647-3 0  9990\n2 40934   6.0033 141.2190 0010344 133.6141 226.4604 14.76056230  5130';
> var jspredict = require('jspredict');
> jspredict.observe(tle, null);
{ eci:
   { position:
      { x: 6780.217861682045,
        y: -1754.945569075624,
        z: -382.1001487529574 },
     velocity:
      { x: 1.8548312182745958,
        y: 7.28225574805238,
        z: -0.6742937006920255 } },
  gmst: 1.2743405900207918,
  latitude: -3.141891992384467,
  longitude: -87.52591692501754,
  altitude: 635.9975103859342,
  footprint: 5474.178485006438 }

Observe a Satellite from an Observer at 15 lat, 130, lon, 10m alt:

> var tle = '0 LEMUR-2 JEROEN\n1 40934U 15052E   15306.10048119  .00001740  00000-0  15647-3 0  9990\n2 40934   6.0033 141.2190 0010344 133.6141 226.4604 14.76056230  5130';
> var qth = [15, 130, .1];
> jspredict.observe(tle, qth);
{ eci:
   { position:
      { x: 6808.890168241923,
        y: -1638.1745052042197,
        z: -392.83171494347425 },
     velocity:
      { x: 1.729088700801128,
        y: 7.313653076194647,
        z: -0.6671038712037236 } },
  gmst: 1.275507328110315,
  latitude: -3.2301661539920232,
  longitude: -86.6090669346031,
  altitude: 636.124394452163,
  footprint: 5474.682764305541,
  azimuth: 75.42118188269167,
  elevation: -70.0809770796008,
  rangeSat: 12666.306550391646,
  doppler: 1.0000075435881037 }

Get Transits for Satellite and Observer (minimum elevation of 2 degrees; obtain a maximum of 4 transits)

> var tle = '0 LEMUR-2 JEROEN\n1 40934U 15052E   15306.10048119  .00001740  00000-0  15647-3 0  9990\n2 40934   6.0033 141.2190 0010344 133.6141 226.4604 14.76056230  5130';
> var qth = [15, 130, .1];
> jspredict.transits(tle, qth, 1446516345242, 1446545135046, 2, 4);
[ { start: 1446519623929.2715,
    end: 1446520436786.1265,
    maxElevation: 26.592307317708126,
    apexAzimuth: 173.44894443969358,
    maxAzimuth: 244.2708297009277,
    minAzimuth: 108.07476128814045,
    duration: 812856.8549804688 },
  { start: 1446525901933.6611,
    end: 1446526693580.5254,
    maxElevation: 24.777958881102588,
    apexAzimuth: 170.71484739848532,
    maxAzimuth: 244.97838417889344,
    minAzimuth: 110.85020906380568,
    duration: 791646.8642578125 },
  { start: 1446532176864.1306,
    end: 1446533027054.9875,
    maxElevation: 20.48579856021555,
    apexAzimuth: 194.49205827738396,
    maxAzimuth: 242.43145831257118,
    minAzimuth: 114.97146874644389,
    duration: 850190.8569335938 },
  { start: 1446538461828.8735,
    end: 1446539183964.2942,
    maxElevation: 15.359176537330036,
    apexAzimuth: 188.34763284223402,
    maxAzimuth: 236.24036969182643,
    minAzimuth: 123.49296057832372,
    duration: 722135.4206542969 } ]
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