Satellites on Google Earth

I have created scripts for tracking satellites in Google Earth. Although I have blogged about these many times over a couple of years now, this page is designed to act a central repository for downloading these files and getting some general information about them.

What Can I Download? These various files are for use with Google Earth (download link). They will show you the current location of different satellites that orbit the Earth. These range from the very well known Hubble Space Telescope or International Space Station to the less well known – but often visible – Iridium Fleet of satellites. KML is the geographical coding language used by Google Earth and Google Maps. You can download the following Google Earth files (KMZ):

• International Space Station (ISS) Tracker
• Iridium Fleet
• Space Science Collection (includes ISS, Hubble, COBE, CoRoT, IRAS, Envisat, Rosat and others)
• Debris from the 2007 Chinese missile test
• Debris from the 2008 US Missile Test – There is no more debris to track.
• Debris from the 2009 Iridium/Cosmos collision
• 100 Brightest Objects in Orbit
• Advanced Satellite Tracker

Using the Advanced Satellite Tracker This is a special script that allows you to input your own TLE data, satellite ID and other parameters. To do this download the file linked above. When it opens in Google Earth it will display the Hubble Space Telescope by default. To alter the tracker you need to enter the ‘Get Info’ properties box in Google Earth (usually right- or ctrl-click on the item in the places list). In the ‘Link’ text box you should see

http://cgi-bin.orbitingfiles.com/anyloc.pl?id=20580

This is the script that generates the KML used to display the satellite(s). You can change or add various arguments to this URL to customise the display.

• id is the satellite’s identifier in the TLE data (default is the ISS, 25544 ,this can also be set to ‘ALL’ to show all the objects in a TLE file)
• url is the source of the TLE data (default is 100 brightest objects from Celestrak)
• hor is a switch specifying whether or not to display the satellite’s horizon (default is Y)
• path is the number of hours flight path to show for the object (default is 2)
• extrude is a switch specifying whether or not to show the tether connecting the object to the ground (default is Y)

As an example, if you wanted to track the new satellites involved in the new European Galileo navigation system, you could use the link:

…anyloc.pl?id=ALL&url=http://www.celestrak.com/NORAD/elements/galileo.txt&path=24&hor=N&extrude=Y

This will show two satellites at very high altitude. A 24 hour flight path is drawn, without a horizon. The line connecting each object to the Earth is shown and the source URL is Celestrak. This is actually a very fun one to do because the Galileo satellites are very far way from the Earth and so they draw most unusual flight paths. This script limits the number of trackable objects to 100. This is to prevent abuse of this tool as early on we had at least one person using it to track 1000s objects, which was killing my server. If you are interested in using this commercially for for very large datasets, feel free to contact me.

How Does This Work? All objects in orbit around the Earth obey the physical laws of gravity, and thus we can predict their location over time. For every trackable object orbiting above our heads, there is a set of parameters called a two line element (TLE) set. These TLE sets are publicly available from services such as Celestrak. The models for predicting the orbit of objects is not perfect though, and so many of these objects are also tracked by radar and this new information is used to update the TLE sets every few days. My scripts use these TLE sets to model the orbits of satellites and predict where they will be at the present time. Thanks to the up-to-date data from Celestrak and the accuracy of the mathematical models, the predicted locations are correct to within a few metres. the same models can be used to predict visible sightings of the ISS and other objects. you can read more about this on my OverTwitter page.

Feedback and Related Blog Posts If you have comments or suggestions regarding these scripts then feel free to contact me. I am always open to feedback and will get back to you when I get the chance. Blog entries on this topic include ‘Satellites on Google Earth‘, ‘Chinese Satellite Debris in Google Earth‘ and ‘Space Telescopes on Google Earth‘. If you’re interested in satellites and, I also have a PDF of a talk about Space Junk that you might find interesting.