144mhz uplink 440mhz downlink

This looks like a workable solution not sure how I would interface amy pcb with the radio though.

AX25 is a good existing and proven protocol. The APRS (ie GPS telemetry piggybacks on this) and you can use the data received to control items. I would have to pick (or PIC) a few other brains to get the hardware sorted. I see no reason for a dual band solution, AX25 being a half duplex mode, it only needs a single frequency to be used.

One of those cheap chinese handhelds could be used very easily, the controller has the PTT controls built in. You just need a tame amateur to tag along, and I would suspect there are a few tagging along this thread.

I should have perhaps mentioned that I am M0RJX which will help in the licenced amature radio operator stakes.

We've probably got all the licencing covered then. AX25 and APRS seem to be the requirements, but we'll need to know what they want us to do with the uplink apart from the abort code and possibly other telemetry we can tag on. 73's de M0DCD

But its not temperature stable

The heater issue can be resolved with minimum issues two options.

1. (EL CHEAPO) De-icing salt insde one zip lock bag and water in another  put salt bag inside water bag before the takeoff  break the salt bag and presto instant heat for about an hour.

2. Buy heating pad that are used for camping.and place them on the inside those barely weigh a damn thing. So it it will keep the inside warm.

The real issue what type of ground antenna are you going to use. Because  to shoot up that high a parabolic antenna is going to be required.