First fire test
To understand what temperatures a stainless steel casing would see during a fire, a peace of 2.5" pipe was buried and a small fire built on top. Eight thermocouples were placed to measure the case and internal air temperature at different depths. This information will be useful in preventing the probe's internal components from heating past their operating ranges.
The data shows the the internal surface temperatures are higher then their outside counter parts. If the ground is treated as a heat sink that is the expected result. Also the lower into the ground, the lower the temperature, which is also expected since the heat source is above the ground.