[j-nsp] Where is RE-850 temperature sensor physically located?

[martin]

I have a M10i router with RE-850(740-011202) routing engine. If I
execute "show chassis environment routing-engine", following
information is printed:

root at M10i> show chassis environment routing-engine
Routing Engine 0 status:
  State                      Online Master
  Temperature                42 degrees C / 107 degrees F

root at M10i>

Where is this temperature sensor located? Is this 42C temperature of
the CPU of the RE0?