What is PICAXE?
Submitted by: srnet
$50SAT is a fully operational satellite in a 600km high Earth orbit using the PICAXE 40X2 processor and RFM22B radio transceiver. Its a new class of satellite called a PocketQube, a concept pioneered by Professor Bob Twiggs of Morehead State University, USA. $50SAT was in the first group of 4 PocketQubes launched and we believe its currently the smallest operational satellite in Earth orbit. The satellite was designed to be simple and low cost to build, well within capability of most schools and colleges. The metal chassis used is just sheet aluminium and angle and needs only the tools of a typical school metalwork shop to build. We made sure that $50SAT was simple to monitor too, the FM Morse beacon can be picked up from about 700km on a low cost UHF receiver. Add a 30minute build antenna and it will be heard at up to 1800km. By measuring the audio frequency of the Morse and the rate (speed) of Morse, you can determine battery voltage and solar charge voltage. All you need to do is feed the audio into a PC for analysis. Other communications methods have allowed data to be received at 2,900kM. The project electronics operates reliably in the harsh environment of Earth orbit so are also well suited for use in near space projects, such as high altitude balloon launches. Both the $50SAT processor\radio board and the ground station receiver board can be used with a GPS as a low cost balloon tracker. The post launch testing of communications on $50SAT has shown that only simple equipment is needed to get data (i.e. tracking information) back from 1000 to 2000km. The solar panel maximum power point controller (MPPC) makes sure the maximum amount of energy is extracted from the solar panel and keeps the single lithium ion battery charged too. The MPPC is also a low cost (and very small) circuit which will find uses in other solar powered projects. $50SAT was built by 3 radio amateurs, Howie DeFelice, AB2S, Michael Kirkhart, KD8QBA, and Stuart Robinson, GW7HPW. The technical plans, PCB layouts and software are 'Opensource' and free to use for educational and personal use, see the $50SAT website for further details.