This technique was used in a slightly different way on NRO satellites. I think KH-7 was the first (GAMBIT http://www.thespacereview.com/article/1279/1 http://ww

This technique was used in a slightly different way on NRO satellites. I think KH-7 was the first (GAMBIT http://www.thespacereview.com/article/1279/1 http://www.thespacereview.com/article/1279/1 ). They would get the film moving at the same speed as the ground that they were covering. The constant momentum of the film moving was easier to counteract than the constant back and forth motion of a big shutter if they were capturing film "plates".