Satellites operate in the vacuum and cold of space, therefore they have to undergo extensive testing here on earth. A few months ago we received a large order for a range of Teflon PFA insulated T-type thermocouples from researchers and manufacturing engineers working on satellites for a large constellation. T-type thermocouples are especially suitable for measuring cold temperatures and are frequently used in cryogenics. And the PFA plastic insulation is very stable at cold temperatures, though brittleness still increases when it is put in liquid nitrogen.
T-type thermocouple wire is available in a range of gauges, AWG 36 (0.125 mm), AWG 30 (0.25 mm) and AWG 24 (0.5 mm) and thermocouples from these wires can be made to any length you need. Contact me to discuss your needs. We also supply T-type extension cables and can make cable assemblies to your specification.