Back in the Sixties I was working at Airborne Optical Division of Baird Atomic. Principally working on spook projects. One of them was being the U-2 aircraft. We built many sensors for the airplane including the Dragon Lady, Smoky Joe and the Pickle Barrel programs.
The things that all U-2’s had in common were the Bubble Sextant and the V/H (velocity over height) unit. Since the places they went they couldn’t use radio Navigation and of course the were no GPS at that time, they had to rely on old fashioned celestial navigation.
Anyone that’s familiar with the old Hawk model of the U-2 can remember a large opening on the panel and that was for the V/H display. This was to synchronize the Itek camera for drift and film speed since the camera was an open aperture and the film had to go at the speed of the aircraft. In all pictures I have seen of U-2s, The sextant and v/h unit was carefully erased out.
There was one U-2 that the pilot bailed out of because of a flame out. The plane landed pretty much intact out in the desert. They changed the engine and patched up some bent metal. They took out all the optical sensors and put them in bonded stores at Baird. This is the plane that Gary Powers flew over Russia since the suspected that the Russians had a missile that would reach a U-2. They guessed right.