The 31st Test and Evaluation Squadron is located at Edwards AFB, Cali., with an operating location at Gray Butte, Calif. The squadron evaluates
the operational effectiveness and suitability of advanced ACC weapon systems by providing operations, maintenance and engineering experts to work
alongside AFMC and Air Force Operational Test and Evaluation Center personnel. Current operational test and evaluation programs involve the B-52, B-1,
B-2, F-22, F-35, RQ-4 Global Hawk, MQ-9 Reaper, and the Airborne Laser. Squadron personnel integrate live test results with modeling and simulation
data to predict combat capabilities under realistic scenarios, setting the stage for the development of new CAF tactics. Results and conclusions
support DoD acquisition, deployment and employment decisions.
from
Elgin fact sheet
Gray Butte is one of the General Atomics facility in the California desert east of Lancaster. I've seen it mentioned in various DoD documents, but
didn't know who the USAF tenant was until I came across this document. I would assume only MQ-9 testing is done by the 31st TES there.
general atomics plant photographs