Our local amateur radio club has been approached by Veikkola junior school with regard to our members participating in the school's proposed High altitude balloon project (Spring 2017); in particular with reference to realizing position reporting (APRS) and possible live stream video imaging.
Given that the target altitude will be approx. 30km, temp -40C(?) and payload capacity 1000g, what sort of power supply should we contemplate, together with any necessary means to keep it warmed?