At the heart of our ballooning program is our tracking system. After all, what goes up must come down, and if we don’t have a tracking system we’ll never recover our payloads! For the past few years we have used a system called APRS, or Automated Packet Reporting System. APRS is a widely used standard in the ham radio community that (roughly speaking) defines a data protocol, a packet protocol and a wavelength. Ham enthusiasts use the APRS standard for many things, but one of the most common is reporting GPS position from a moving station (car, boat etc.). APRS is so popular that many ham radio operators have set up automatic radios that automatically receive APRS packets and forward them to databases on the internet where they can be freely plotted and followed on a map. We use this to follow our flights on http://aprs.fi/ when we are not in the chase vans.
The tracking system for our ballon system has two parts. On the balloon end we have a commercially available BeeLine APRS system from Big Red Bee. The BeeLine contains a GPS system, a Terminal Node Controller (TNC) and a radio transmitter. The TNC is essentially modem for the radio, translating the GPS data, once a minute, into a series of audio tones that are transmitted via the radio transmitter.
On the ground, in the chase vans we have a Kenwood radio with a built in TNC. Tuned to the right frequency (in this case 144.390MHz), it will interpret the incoming radio signals and output a serial port stream of characters for each packet. To extract the position from this packet and plot it on a map, we rely on a laptop running two programs: UI-View and Precision Mapping. UI-View reads the serial port and translates the APRS packets into a set of positions. It then requests a map from Precision Mapping and plots the balloon position on this map.
The set of these two programs has been very useful and has allowed us to make dozens of successful flights, but they are very frustrating to use and lack many features that we really would like to have:
- The map interface is quite old and navigating it is difficult and unintuitive. The interface also shows only the most recent position. Finally, the only map available is a street map. Satellite views are unavailable.
- Only a single person can use the software at a time.
- There is no ability to do a live prediction for the landing location
What we would really like is a system that is as easy to use and intuitive as Google Maps, can be used by everyone in the van, and allows us to “crunch” the APRS data to produce predictions, plots, etc. The current system isn’t extendable so we have decided to go ahead with the development of an entirely new tracking software based on a more modern web-app paradigm.
Ted Freeman is leading the Far Horizons Tracking Software efforts. If you have any questions or would like to contribute, just give a shout. We need help in programming, design and testing. A good tracking software system would be a major improvement for our program.
This weekend the Adler is hosting Hack Day Chicago so the place will be crawling with hundreds of programmers, tinkerers, hackers and just generally fun folks. If you missed your chance to register for the events you can still come in to the lab and enjoy a day of hacking on Far Horizons!
Don’t forget that next weekend the Adler will be closed for the NATO summit. So no Lab Saturday on May 19th!