Telescopic Sighting SystemThe Telescopic Sighting System was a sight used on the FV4201 Chieftain tank and RAF F-4 Phantom aircraft.UsageThe TESS was trialed and introduced in the early 1980s originally as a tank sight for the FV4201 Chieftain. Surplus stocks were used on F-4 Phantom aircraft operated by the Royal Air Force as a cost-saving measure for a long range daytime Automatic [target recognition|target identification] device, whereas the United States Air Force used the TISEO on their F-4 Phantoms. The TESS was installed in the rear cockpit in the centre window section for the Radar Intercept Officer to use. It was boresighted to the aircraft weapons system and when locked on target, the target was magnified six times.