So, balloon will be attached to the payload box via rope which has two things attached to it: a parachute and a radar reflector. Reflector is there so aircraft can see the contraption, the parachute will be open all the time, but doing nothing as the balloon ascends.
Once the balloon bursts (somewhere over 30km) the parachute will slow the fall.
Throughout the payload will broadcast its location derived from GPS over a 433Mhz link (probably RTTY) which I can track. Once at a low altitude (not sure how low yet) and within GSM range the payload will also SMS its location to another cell phone.
This should give me enough data to find the balloon. Plus there is software to do balloon trajectory prediction based on weather forecasts. That'll give me a general idea of route as well.
Also, on a clear day the entire thing will be visible from the ground using high-powered binoculars or a small telescope. If I have time I'd like to get automatic ground tracking in place by attaching a Yagi antenna to a powered telescope and using the downlinked balloon location to steer the telescope to train the antenna on it and to get video of the balloon's ascent. That last part may be beyond my budget unless someone's got a steerable telescope mount that has a computer interface (RS-232/423 or USB) that they'd like to give me :-)
I plan to use a small video camera that will be activated at altitude to record HD video of near space (and the descent). Currently thinking of a Slide HD which can record 4 hours of video and is small and light, but this part isn't nailed yet.
This is actually a really complex project: navigation, telemetry, all the balloon related aspects, interface with ATC, temperature extremes, weather, ...
This sounds really ambituous. I seriously hope your plan will succeed! Just be sure to document the whole adventure in a.series of blogposts. Project like that is bound to top HN's front age in an instant.
I want to downlink some pretty simple information: lat, long, altitude, temperature, so I think RTTY should be good enough. There are some nice modules by Radiometrix which work on 433Mhz (unlicensed band in the UK) (e.g. http://www.radiometrix.com/content/ntx2). The CU Spaceflight folks have been using these modules at 50 baud. I think I'm going to stand on their shoulders for this part.
Once the balloon bursts (somewhere over 30km) the parachute will slow the fall.
Throughout the payload will broadcast its location derived from GPS over a 433Mhz link (probably RTTY) which I can track. Once at a low altitude (not sure how low yet) and within GSM range the payload will also SMS its location to another cell phone.
This should give me enough data to find the balloon. Plus there is software to do balloon trajectory prediction based on weather forecasts. That'll give me a general idea of route as well.
Also, on a clear day the entire thing will be visible from the ground using high-powered binoculars or a small telescope. If I have time I'd like to get automatic ground tracking in place by attaching a Yagi antenna to a powered telescope and using the downlinked balloon location to steer the telescope to train the antenna on it and to get video of the balloon's ascent. That last part may be beyond my budget unless someone's got a steerable telescope mount that has a computer interface (RS-232/423 or USB) that they'd like to give me :-)
I plan to use a small video camera that will be activated at altitude to record HD video of near space (and the descent). Currently thinking of a Slide HD which can record 4 hours of video and is small and light, but this part isn't nailed yet.
This is actually a really complex project: navigation, telemetry, all the balloon related aspects, interface with ATC, temperature extremes, weather, ...