The entire RDF beacon (batteries, controller, transmitter, antenna) will be packaged into a "hula hoop" (about 1.5m dia) made out of 1" PEX tubing. This hoop is what the shrouds of the parachute are tied to. It is used to hold the parachute canopy open so that the parachute catches air as soon as the balloon falls into sufficiently dense air to provide drag. The hoop goes along for the ride on every launch. This way the RDF beacon doesn't occupy a "spot" that would normally be used for student-built payloads. The hoop is visible in **broken link removed**. The wall of the tubing is only about 1mm thick, so it is not going to provide much insulation.
My goal is to make this beacon as robust and simple as possible. The other "trackers" are too complex, they are dependent on a line-of-sight radio path to an APRS digi-peater, GPS lock, etc.
I want to make mine dirt simple, no GPS, no external dependencies on LOS to a digi-peater, etc, simple primary batteries. One idea is to have the PIC execute code with counting loops for the timing so that the chip self heats, rather than shutting down then cpu and using the super low power timers. I could put a little bit of foam insulation around the PIC.
Which types of capacitors do best a extremely low temps?