Part 107 UAS crew member reported operating in their approved area at a non-towered airport when a military transport aircraft entered the area near the UAS and did not communicate on the CTAF. The aircraft took evasive action and then departed the area.

Narrative

During a normal flight operation of our UAS we experienced an encounter with a low level Aircraft Y at ZZZ. Our typical area of operation is in the North West corner of the airport property at or below 400 ft. AGL. Our flight area is 1;500 ft. and greater west of centerline and directly west of the numbers on the departure of Runway XX. We were operating well below that at roughly 180 ft AGL (5;200 ft. MSL exactly). We were monitoring radio frequency and listening to the other traffic in the pattern. We have a NOTAM filed; and our operation is described in the remarks on the AWOS at ZZZ. The Aircraft Y appeared without a radio call; from our north east; in a steep 60-70 degree bank to the left. It appeared that it had made a low level pass over Runway XX and made a left hand departure at low level; entering our operation area. We attempted to communicate among the ground crew to command the helicopter to a safe area; but with the closing speed of Aircraft Y at approximately 150 kts approaching our UAV which was at 25 kts ground speed there was no time to maneuver. In the short amount of time I had to make a radio transmission notifying Aircraft Y pilot that our UAV was at its altitude and they were approaching it from behind. Aircraft Y then rolled hard to the right and departed to the west of the field at low level; never exceeding roughly 400 ft. AGL; and skimming the hilltop heading west to Location A. The closest lateral distance is estimated at approximately 1;500 ft.; with near zero altitude separation. No incident occurred and no further communication was conducted between aircraft.It is likely that Aircraft Y pilot was unaware of the NOTAM or AWOS information describing our location and operation. It is also possible that terrain obstructed any call Aircraft Y pilot made about his intentions; leading to a delay in our ability to respond to their presence at a very low altitude and in an unconventional path for the airport.We actively monitor air traffic using Flight Radar 24; Foreflight; and Flight Aware. Aircraft Y was not broadcasting any positional data on any of those mediums; so we were unable to identify the aircraft or obtain their ground track prior to the interaction.