Tracking Satellites With Arduino

With the recent progress in software defined radio hacks (rtl-sdr), receiving and decoding radio signals is now easier and cheaper than ever! 

While the original FPGA based software defined radio (SDR) platforms cost around $1500 minimum,  now a $30 DVB-t dongle can be purchased on ebay and hacked with some custom drivers to perform the exact same task (with the exception of being able to transmit a signal). All of a sudden everyone can tune into and decode (given the right software) everything that lay between the  52 - 2200MHz frequencies. 

Among the many interesting signals, the one that caught my attention was was the NOAA weather satellite's automatic picture transmission (APT) downlink that is on around 137.100MHz (for NOAA-19). As the NOAA satellite comes over the horizon line, it is possible to start capturing and decoding the signal into live weather images (provided you have the right antenna and have a relatively good view of the horizon), now that sounds like a relatively easy task to accomplish until you consider that unless you have a right hand circular polarised antenna (i.e a Quadrafilar Helical Antenna) sitting 3 stories high you will be trying to deal with capuring the signal, adjusting the tuning as the satellite moves past to compensate for the Doppler effect, tracking the satellites position with other software.... all whilst trying to aim a directional antenna (likely a yagi or dipole) as accurately as possible at the satellite! 

Not to mention that if your serious, all of this goes down in about 10 minutes at around 3am, so unless you are prepared and well practiced, the chances of getting anything useful are pretty slim.

So this brings me to the satellite tracker, the objective of this project was to be able to track satellites live using the current GPS location, and in the near future add a compass module / accelerometer to either provide user feedback on the current 'accuracy' of their aiming, or to fully automate the aiming process using stepper motors. IMHO latter would be preferred.

The tracker uses the PLAN13 algorithms by James Miller to track the satellites using NORAD issued two line element (TLE) data sets.  Multiple satellites can be tracked, they just need their own TLE variables declared, you can then simply pass the variables for every satellite you want to track into the PLAN13 library (courtesy of +Bruce Robertson 's qrptracker) and it will return the azimuth and elevation for that satellite at you current location.

for example....

The PLAN13 library I used (modified for >>Arduino 1.0) can be found here. Please note: This software is beer-ware, please donate a beer below if you use this code :)