Author Topic: "Ground truth" - Corona landmarks  (Read 1276 times)

Online Oersted

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Offline Archibald

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Re: "Ground truth" - Corona landmarks
« Reply #1 on: 04/11/2017 06:25 PM »
That's... amazing. Then it make sense. How do you calibrate a spy satellite, and test its resolution ? I wonder which engineer came with that solution. His coleagues must have thought "he is crazy".
... that ackward moment when you realize that Jeff Bezos personal fortune is far above NASA annual budget... 115 billion to 18 billion...

Online Blackstar

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Re: "Ground truth" - Corona landmarks
« Reply #2 on: 04/11/2017 06:47 PM »
That's... amazing. Then it make sense. How do you calibrate a spy satellite, and test its resolution ? I wonder which engineer came with that solution. His coleagues must have thought "he is crazy".

Resolution test targets existed before CORONA. They were often put on airfields, because that's where the recon planes launched from. There were many complex variations on them. The Soviets had them as well.

Online Blackstar

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Re: "Ground truth" - Corona landmarks
« Reply #3 on: 04/11/2017 07:04 PM »
I'd have to go dig through my materials, but I think that there are two different relevant ground markings:

-calibration markers
-resolution test targets

The resolution test targets had a bunch of white bars of different sizes and distances from each other. These were often located at airfields. There were even portable version (which I think were primarily just pieces of white painted plywood that could be picked up and loaded into a truck).

I think that these calibration markers mentioned in the article were not for determining resolution, but for calibrating the cameras, possibly the mapping cameras (as opposed to the main reconnaissance camera). What the users, and the camera developers, needed to know was what the distance between two points on the film was compared to the ground distance. If you have a square piece of film, and you cover it with equally-spaced dots, are all the dots on that film the same ground distance from each other? Or are the dots near the edges farther apart than the dots near the center? I think that these ground targets were used for that purpose.


UPDATE: The things in the article were known as Controlled Range Network (CORN) targets.
« Last Edit: 04/11/2017 07:43 PM by Blackstar »

Offline whitelancer64

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Online Blackstar

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Re: "Ground truth" - Corona landmarks
« Reply #5 on: 04/11/2017 07:46 PM »
Another article with some better pictures:

http://99percentinvisible.org/article/solve-x-deciphering-calibration-marks-made-classified-spy-missions/

That article also includes the resolution test targets I mentioned.

This story reemerges every few years as a reporter suddenly re-discovers these things.

You can find more info here:

http://journals.sagepub.com/doi/abs/10.1177/107118137702100205


Offline Star One

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Re: "Ground truth" - Corona landmarks
« Reply #6 on: 04/11/2017 08:26 PM »
I wonder if the the KH-11 fleet still need to use things like this?

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