It has been a while ago since I retrieved the BallastHalo 4 Balloon but the last few months I regained my interest to High Altitude Balloon (HAB) experiments.
Almost every week one or more High Altitude Balloons are launched in Europe by radio amateurs and students. The balloons are made of Latex or Mylar with a parachute and payload underneath.
In the payload the hardware varies but always contains a GPS, micro-controller and a small transmitter. Most payloads also have sensors (eg. for temperature and air pressure) and sometimes photo and video equipment on board.
All the European HAB payloads uses small 70cm band transmitters with an output power of 10 or 25 mili Watt which can be tracked with a receiver capable of SSB reception and a PC for decoding the rtty data.
A lot of information about High Altitude Balloons and the technique can be found on http://ukhas.org.uk/. Tracking and balloon position can be viewed live on http://spacenear.us/tracker/.
At the moment I'm busy designing my own High Altitude Balloon payload. It's build around an Arduino Uno micro controler. On the bread board you can see the Radiometrix NTX2 70cm 10mW transmitter, UPU/uBlox GPS , Parallax Pressure/Temperature sensor and a SD card module for storing all the data.
The final goal of the design is to replace the Arduino Uno with the Pro Mini (the small PCB on the bottom of the photo).
When the payload and software are ready I hope to launch my HAB into near space. Near space is a lot higher than airplanes do. They fly at an altitude of 10km and High Altitude Balloons go above 30km. The current Amateur HAB altitude record is almost 43 km (42687 meter)!