NRO Declassifies KH-9 Satellite 74
schwit1 writes "The Big Bird, formally known as the KH-9 Hexagon satellite, was first placed in orbit in 1971 after its development by the National Reconnaissance Office (NRO), making it one of the most advanced spy satellites of its time. It is believed to have produced images of the Soviet Union, China and other countries that held strategic importance for the U.S. government through the Cold War. But it was never seen outside the intelligence community. This weekend, it will be available for all in the Washington area to see, but only for one day. To celebrate its 50-year anniversary, the NRO, along with the Smithsonian Institution, is for the first time publicly displaying the newly declassified relic at the Steven F. Udvar-Hazy Center in Chantilly, Va. In doing so, the intelligence agency is prompting more than just a little bit of excitement among reconnaissance experts and technical hobbyists."
Re:The obvious question: why is there one to see? (Score:4, Informative)
It was probably the last one on the production lineup, and got the launch got scrubbed because something better came out, and instead of wasting a Titan launch on something obsolete, they changed plans. TFA didn't say this particular bird was launched in 1971, or at all, just that the first one flew in 1971.
Re:Resolution (Score:5, Informative)
Consumer-grade 35mm film has about 3000 grains per inch average, so each frame has a granularity of about 4000x3000. However, the photochemical process by which grains are exposed and fixed does not happen on a regular grid (like pixels do), and favors clustering of grains especially at edges. There is a nominally (except for texture of the backing medium) infinite degree of subgrain positions exposed grains can get fixed to when developed.
So while a 370NM distance might be covered by 4000 grains, about 171 meters per grain, the shapes defined by grains around features in the subject could possibly represent much finer sizes, perhaps down to several dozen feet.
Another factor is the nature of the subject. If you can tell from a fuzzy zoom simply whether or not a shape is dark or light, you might be able to tell whether a garage door (or missile silo) is open or closed, or empty or full. You might be able to tell that a light is on in an office at night. You might be able to tell that a line of tanks is arrayed, not a chainlink fence. A big part is the human eye and mind's ability to recognize shapes in fuzzy analog blotches, especially from a short list of possible answers. Which is what the majority of intelligence relies on: getting context, not just the target data, and making reasonable inferences.