High temperature reading of mechanically-separated body
I am working on something similar at work as a side project. It's to measure currents on a rotating winding. I've decided to go with IR LEDs and photodiodes as a communication link with multiple LEDs being driven in parallel so one of them is always in view by the photodiode.

It isn't clear whether a rotating connection is allowed. If it is, you could also go with slip rings, of either mercury or fiber optic kind. That's the classical method.

A more novel idea that only works because you're measuring temperature is to have a device that reproduces the temperature measured at the temperature sensor somewhere on the rotating wheel where it is exposed and could be measured that with a thermopile or IR thermometer. A third temperature sensor would be required on the shaft itself so it could monitor the temperature of the exposed area and adjust it as necessary to match the internal temperature sensor.

Given the high ambient temperture and noisy environment, this actually might be simpler and more straightforward than any of the other methods which which require processing to occur within the chamber or on the shaft. The main hiccup is how to provide enough power for the exposed temperature element and how to provide lower than ambient temperatures if they are possible. A peltier element might be able to be used to provide both above and below ambient.