Javascript library for predicting the visibility timings and path of satellites (e.g., Starlink) for a given location and time.

This library powers findstarlink.com and has served millions of satellite visibility predictions over the past 6 years.

npm install sat-timings

Require the library in your Node.js project:

const predict = require('sat-timings');

const predict = require('sat-timings');

// Example satellite object (from TLE data)
const sat = {
	name: "starlink-1000",
	title: "Starlink-1000",
	tle: [
		"1 44713U 19074A   21275.12345678  .00001234  00000-0  10270-4 0  9991",
		"2 44713  53.0000  67.0000 0001000  90.0000 270.0000 15.05555555    10"
	],
	stdMag: 5,
	launchDate: "2020-04-22"
};

const latitude = 51.5072; // London
const longitude = -0.1276;

const result = predict.getVisibleTimes(sat, latitude, longitude, { daysCount: 5, startDaysOffset: -1 });
console.log(result);

The result is an object with fields like:

{
	"currentLocalTime": { "time": "6:21 pm", "date": "23 Jan 2020", "epoch": 1579861567 },
	"tleDate": 1579861567,
	"timezone": "Europe/London",
	"sunrise": "5:45 am",
	"sunset": "6:32 pm",
	"timings": [
		{
			"name": "starlink-1000",
			"title": "Starlink-1000",
			"visibility": "good",
			"start": { "time": "7:43 pm", "date": "24 Jan 2020", "epoch": 1579861567 },
			"end": { "time": "7:48 pm", "date": "24 Jan 2020", "epoch": 1579861883 },
			"mins": 5,
			"brightness": 2.4,
			"brightnessText": "bright",
			"startDir": 243.55,
			"startDirText": "southwest",
			"endDir": 35.5,
			"endDirText": "northeast",
			"startElev": 12.45,
			"maxElev": 76.33,
			"endElev": 40
		}
	]
}

const path = predict.getSatellitePath(sat, 90); // 90 minutes window
console.log(path);

{
	"startEpoch": 1579861567,
	"path": [
		[51.5, -0.1],
		[51.6, -0.2],
		...
	]
}

• sat: Satellite object with fields { name, title, tle, stdMag, launchDate }
• latitude, longitude: Observer's location
• options (optional):
  • daysCount: Number of days to predict (default: 5)
  • timeOfDay: 'morning', 'evening', or 'all' (default: 'all')
  • startDaysOffset: Offset from today (default: 0)

Returns: Object with current time, timezone, sunrise/sunset, and an array of visible timings.

• sat: Satellite object
• mins: Minutes window (default: 90)

Returns: Object with startEpoch and array of [lat, lng] pairs for the satellite path.