Very rare beast - RC-135U Combat Sent

The RC-135U Combat Sent is one of the many derivatives of the Boeing RC-135 family of large reconnaissance aircraft. It is designed to collect technical intelligence on enemy radar emitter systems. Combat Sent data is collected to develop new or upgraded radar warning receivers, radar jammers, decoys, anti-radiation missiles, and training simulators. There are only two in existence, both usually based at Offutt airforce base in Nebraska, USA. I was lucky enough to see one on a deployment to Mildenhall - it apparently had been information gathering on Russian submarine activities in the Barents Sea.