Riddle Me This… Gambit PET Reports

At some point over the last Christmas break, I got bored. I should have been planning my post-graduation future (oh, wait… I’m already employed), but I spent many hours making incessant FOIA requests to the NRO. If you want to know what excess is – there were 38 (KH-7) GAMBIT and 54 (KH-8) GAMBIT-3 launches. Throw in the 19 successful KH-9 HEXAGON missions and you’ve got a LOT of FOIA requests to sift through.

But to be fair, I got distracted halfway through (“Squirrel!”) and didn’t complete the series for the KH-8 missions. The rest are still on my “To-Do” list. For the FOIAs I completed, many have already been released and sent to me via FedEx. If you’re wondering where a percentage of the NRO’s budget goes, I can safely say it comes to me… through FedEx.

The Mission 4008 Performance Evaluation Team (PET) report included this image. This looks like a weird Pablo Picasso-esque nightmare or a prototype for the next Ugly-Doll series:

The crispness of the above image is due to the fact this was NOT taken from a satellite – it came from a specially modified RB-47 carrying a KA-2 camera at 16,500-feet during what was known as a “BLACKBIRD” mission.

The weird broken lines are CORN Tri-bar targets set up in a “T” pattern; the half-circle “evil eye” is a CORN bullseye target. And the “X”? Probably is where the Goonies’ treasure is buried.

Same CORN Target captured by M4008 on Rev 15

This above image was taken by M4008 during revolution 15. Note how the staggered lines can still be individually distinguished near the bottom part of the left hand line, along with the marks near the center of the photograph. The perpendicular layout allowed photo interpreters at the Air Force Special Projects Production Facility (AFSPPF) to determine resolution in for both cross-range (off-nadir, perpendicular to orbital motion) and down-range (following orbital motion, aka which direction the vehicle was heading).

Big words, simple explanation: see how the aircraft shot is clear… and the satellite shot is clear too.

The PET report determined that the satellite image resolution was around 2.24 feet.

M4008 PET Report, Section V

Now, remember that the width of the Casa Grande crosses are nearly 60-feet across.

Coarse cross measurement, courtesy of Google Maps

Bar dimensions, length and width, conform to the aspect ratio as defined in Mil. Std. 150A, i.e., length of the bar will equal five times the width of the bar. Those spaced bars you can actually see at the end of the CORN Tri-bar lines? Those are the A1 panels.

A1: Bars are 4ft wide, 40 feet long

So if you can see the a definitive space between the farthest white bars – and they’re not globbed up as one – your image has at least a ground sample distance (aka ground resolution) of 4-feet. And as you can easily see, you can view ground resolution less than 4-feet.

The NRO reports list many instances of GAMBIT imagery “better than a foot” based on CORN target analysis. Officially, I don’t know what the best resolution was… but “better than a foot” came directly from NRO documentation, so we’ll go with that. CORONA, as a search system, had less resolution than GAMBIT but still below the 60-foot limits provided by the crosses.


Let’s flip this information on its head: how can you determine ground resolution with a 60-foot target (that has fixed length on all four petals), but is spaced at least a kilometer away from its nearest “neighbor”?

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