Also interesting are the resolution targets, using sets of black and white bars at varying widths in both X any X orientation, to determine the spatial resolution i.e. how high frequency a component could still be imaged separately as lines, similar to TV test cards. These are discussed in various blogs [1][2] with some amazing picures. I think these were for both satellite imaging and spy-plane (U2 and SR-71 plus less exotic surveillance systems) and not just the USA. This article [3] shows some satellite test targets in the Gobi desert, presumable for Chinese (PRC) spy satellites, and also has a cool picture of the world's largest compass rose, at Edwards dry lake bed, as well as explaining the crosses from the original article, and talking about radar altimeter targets (another dry-lake bed) that are mapped to centimetre accuracy in altitude for calibrating GPS and other systems.<p>I find it a really interesting area of industrial/scientific archaeology, with some fascinating stories.<p>[1] <a href="http://www.clui.org/newsletter/winter-2013/photo-calibration-targets" rel="nofollow">http://www.clui.org/newsletter/winter-2013/photo-calibration...</a>
[2] <a href="http://www.bldgblog.com/2013/02/optical-calibration-targets/" rel="nofollow">http://www.bldgblog.com/2013/02/optical-calibration-targets/</a>
[3] <a href="http://www.atlasobscura.com/articles/landscapes-made-for-satellite-eyes-calibration-targets-resolution-tests-and-giant-desert-compasses" rel="nofollow">http://www.atlasobscura.com/articles/landscapes-made-for-sat...</a>
My dad was project photogrammetrist on Corona when he worked at Itek in the 60s. Lots of stories around focus and aiming challenges, since Corona was used to build maps of inaccessible regions of the world (e.g. Soviet Union ICMB sites). Focus targets gave high contrast, known images to detect what kind of focus problems were being encountered -- ranging from image smear from forward motion compensation failing or stretching the film; film sticking, stretching and/or lifting off of the focal plane; star camera inaccuracies; thermal distortion of camera, spacecraft, star camera, or film; etc. A few good books on Corona (<a href="https://www.cia.gov/library/publications/intelligence-history/corona-between-the-sun-and-the-earth" rel="nofollow">https://www.cia.gov/library/publications/intelligence-histor...</a>) and Itek (<a href="https://books.google.com/books/about/Spy_Capitalism.html" rel="nofollow">https://books.google.com/books/about/Spy_Capitalism.html</a>) out there. Same teams worked on subsequent KH projects (Gambit, Hexagon/Big Bird/BMF), as well as Apollo and Viking camera systems.
I love stuff like this, I just think its so cool. Similar to this are the large cement arrows across the US:<p><a href="http://www.cntraveler.com/stories/2013-06-17/transcontinental-air-mail-route-maphead-ken-jennings" rel="nofollow">http://www.cntraveler.com/stories/2013-06-17/transcontinenta...</a>
One of the most interesting things about the Corona satellites was that they shot on film and that film was developed back on earth.<p>So how'd they get that film back down from space?<p><a href="https://en.wikipedia.org/wiki/Corona_(satellite)#Recovery" rel="nofollow">https://en.wikipedia.org/wiki/Corona_(satellite)#Recovery</a>
The Corona project. A/K/A the KeyHole satellites. If my count is right, 135 satellite launches, though not all were successful.<p>Fun fact: this was the early 1960s. CCD technology and IP transmission bitrates were a bit primitive[1], so the <i>film</i> cameras would eject capsules after they'd been shot, which would re-enter the atmosphere and be recovered, most through mid-air retrieval. The project was active from 1959 to 1972.<p><a href="https://en.m.wikipedia.org/wiki/Mid-air_retrieval" rel="nofollow">https://en.m.wikipedia.org/wiki/Mid-air_retrieval</a><p><a href="https://en.m.wikipedia.org/wiki/Corona_(satellite)" rel="nofollow">https://en.m.wikipedia.org/wiki/Corona_(satellite)</a><p>Video of recovery: <a href="http://petapixel.com/2014/08/31/us-spy-satellites-used-drop-photos-film-buckets-space-airplanes-catch-mid-air/" rel="nofollow">http://petapixel.com/2014/08/31/us-spy-satellites-used-drop-...</a><p>______________________________<p>Notes:<p>1. Well, technically they didn't exist.
The in the story linked movie about the Corona Project is an amazing document of history.<p><a href="https://archive.org/details/gov.archives.arc.1678526" rel="nofollow">https://archive.org/details/gov.archives.arc.1678526</a>
Anyone know what's nearby there at about (32.92669, -111.922201)[0]? It looks like some sort of strip mine a few hundred feet to the north, so I assume it's related, but was just curious what it is. It looks like a painting!<p>[0] <a href="http://maps.apple.com/maps?ll=32.926699,-111.822201&spn=0.006796,0.014104&t=k" rel="nofollow">http://maps.apple.com/maps?ll=32.926699,-111.822201&spn=0.00...</a>
Here's a map of them. Corrections and additions welcome.<p><a href="https://drive.google.com/open?id=1bebA9E6kTb3G9g5GEeezYPzvwHo" rel="nofollow">https://drive.google.com/open?id=1bebA9E6kTb3G9g5GEeezYPzvwH...</a><p>Based on the map from wikipedia, which had 84 locations, this has 120.
Interesting: I've submitted this story over a day ago (<a href="https://news.ycombinator.com/item?id=12684118" rel="nofollow">https://news.ycombinator.com/item?id=12684118</a>) with a <i>clean</i> URL, yet this submission got noticed?<p>Yes, good luck and good timing, but still - ha!
They could have embedded LOVE instead of X's and it wouldn't have created any mystery and unneeded attention, as everyone would know it was hipsters.. no, I mean hippies.. =D