I want to try and demonstrate on this page some of the things that make Linux such a superb operating system. The STSPLUS software mentioned on the main spacewatch page is all well and good if you're using MS-DOS, but there isn't anything currently available for Linux which offers the same features in a single program. If Linux wasn't the kind of OS it is, we'd be stuck at this point. But, happily, there's a solution to the dilemna, in that we can take some smaller bits of software, bolt them together and make our very own suite of programs for tracking satellites under Linux. Folow these steps through...

An accurate clock on your computer is an absolute pre-requisite to all of this. You can synchronise your systems clock to any one of a number of public time servers out on the Internet. These time servers are generally kept in synch with an extremely accurate clock, such as an atomic clock, so you can keep your system time accurate to within 1 or 2 seconds quite easily. See the timekeeping page for full instructions.

Orbital mechanics is a complex subject, and I don't pretend to know very much about it. The first thing we're going to need, therefore, is some software which can handle the maths required to calculate the position of a spacecraft at any given moment in time, based on information provided to it about the orbit that the spacecraft is currently in around the earth.

The particular program I'm going to use is Predict version 2, so download it and put the source tarball somewhere useful in your home directory, then look at the installation instructions to get it going.

One of the features of Predict which makes it extremely useful for this project is its provision of a 'server mode', where it will sit there happily calculating spacecraft positions and making the information available via a network connection. You can then employ a suitable bit of software which collects this information and uses it to display a nice picture of where the spacecraft is in relation to your own location.

This step is relatively simple...you'll need to become root on your system first, though. Open a terminal session and use the same 'su -' command as before. Using your favourite text editor, open up the file /etc/services, and add the following 2 lines to the bottom:

# local stuff
predict         1210/udp
		

The program I'm going to use for this part comes included with the Predict-2.2.x source distribution. You need to compile and install it as follows:

    cd /usr/local/predict/clients/gsat-1.1.0
    ./configure && make && make install
		

Once all the garbage has finished scrolling up the screen, and assuming there aren't any error messages, type 'exit' to return to your normal login. If you now type the command 'gsat &', you should see the following window appear:

Update October 27th 2003: You may find that the compile process ends with a series of error messages similar to the following:

/bin/sh: line 1: /usr/bin/ginstall: No such file or directory
make[2]: *** [install-binPROGRAMS] Error 127
make[2]: Leaving directory `/usr/local/predict-2.2.2/clients/gsat-1.1.0/src'
make[1]: *** [install-am] Error 2
make[1]: Leaving directory `/usr/local/predict-2.2.2/clients/gsat-1.1.0/src'
make: *** [install-recursive] Error 1
		

If so, type these commands:

ln -s /usr/bin/install /usr/local/bin/ginstall
rm -f config.cache
./configure && make && make install
		

You should then find that everything works as expected.

Here's the exiting bit...in your terminal session, type 'predict -s' to start the Predict-2.2.x server. It will go straight into multi-satellit tracking mode and start calculating spacecraft positions. Go back to the gsat window and click the 'connect' button. You should see this:

click the 'connect' button again, and the gsat window should start displaying spacecraft information. The screenshot below shows how it looks with ISS selected as the target spacecraft: