[pocketstar]

NASA’s box requirement is 70C. That means the ICs in the box are much hotter, parent is probably refering to IC temp, not unit.

[geomark]

There were some non-NASA boxes that had long periods powered off on the shaded side of the bus and had to operate at powerup at initially very low temperature. And then operate on the sun side for extended periods at an elevated temperature. Depending on the configuration of the bus there were sometimes challenging heat transfer issues. The plate temp wasn't 125 C (I don't remember the exact number) but there was assumed a significant temperature rise from the plate to the electronics. And then additional margin added on to that in case something wasn't quite up to spec in the thermal path. So we had to perform worst case analysis assuming junction temperatures of 125 C. It was pretty awful.

[madengr]

Ok, makes sense. The 70C for my unit was the temperature of the plate to which the PA was mounted.