CORONA and other declassified images can be acquired through the USGS data distribution site, EarthExplorer. While originally sold as either contact prints or films, today CORONA are scanned and distributed as TIFF images. Scanning is undertaken using a photogrammetic scanner to minimise additional spatial distortions created during the scanning process, although some issues remain (Gheyle et al. 2011). In addition, the long film strips on which CORONA images were captured require them to be scanned in three or four separate, overlapping segments (see Orthorectification of complete CORONA scenes). The USGS offers lower resolution (14 micron) scans of CORONA, but in order to get the highest resolution from the film, researchers should be sure to request scans at 7 microns, which approximates the grain size of the film itself. Note that images generally cost $30 each, unless they have been recently scanned by the USGS, in which case they can be downloaded for free. To find CORONA images on EarthExlorer, simply select 'Declass 1 (1996)' under the 'Declassified Data' option. To limit the search to only KH-4B images, select 'Stereo High' under 'Camera Type' in the 'Additional Criteria' tab. KH-4 and KH-4A images can be found by selecting the 'Stereo Medium' option. These raw images contain severe spatial distortions caused by the unusual panoramic camera system employed by the satellites, and these distortions must be corrected before images can be used for most mapping applications. We describe our own as well as other methods for correcting imagery in section 2. Around 1200 geometrically corrected images are currently available to view and download through our custom-built website.
CORONA images each have a unique image designator in the format, DS11021025DA042. These designators can be parsed as follows:
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| File last updated: Fri Sept 21 2012