After researching near space balloon projects and launching two of my own I've found that the major hurdle is in communication with the balloon payload. Many near space ballooners are using HAM radio equipment to track their balloons through triangulation or APRS data transmissions. That's all well and good if you have a HAM license and the experience to know what equipment and frequencies to use. The non-HAM ballooners are using cellphones or cellular modules to send SMS messages for tracking the flight. Cellular modules work pretty well up to 40k feet altitudes with good external antennas, but above that altitude there will be no communication from the payload. It's a bit nerve racking not knowing what's going on with the payload for more than half of the flight. Cellular coverage isn't always available in the best launch locations in the U.S.
I discovered that the communications challenge is very simple with the right hardware. The XTend900 radio from Digi (http://www.sparkfun.com/products/9411
) and a high gain patch antenna (http://www.l-com.com/item.aspx?id=20447
) can keep you in communication with the payload for the entire flight and can even provide enough bandwidth to transmit small pictures. This instructable will focus on the minimum set of hardware to get you into near space, capture those spectacular photos, and track your payload to recovery.
For information on my last near space flight, Night Sky, visit www.wildfirerobotics.com/nightsky