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[转载]KH-8的分辨率的分析  

2012-03-09 21:05:06|  分类: Space |  标签: |举报 |字号 订阅

  下载LOFTER 我的照片书  |
NRO公开的文件,大多数人只看了factsheet里那个小于2英尺。实际呢,根据对这些文件的仔细分析,是达到了0.1米甚至更高的。
NSF的帖子还是很不错的:
http://forum.nasaspaceflight.com/index.php?topic=26821.15

Here are some more musings on the ground resolution (since the actual numbers have been redacted quite inconveniently):

Fig. 5 in The KH-8B Camera System (Doc #17 in the GAMBIT folder) visualizes the KH-8B primary camera (175.6" focal length) frame coverage, which results in a 3.4 nautical mile (6,300 meter) wide swath. Fig. 7 shows that the main image is projected on a 8.811" (223.8 millimeter) wide portion of the film. This yields a ratio of ground coverage to film width of 6,300 meter / 223.8 millimeter or 28.15 meter / millimeter.

The GAMBIT Story has a section on GAMBIT Films (page 85):

Developed by Kodak … these films evolved from the original Type 3404, through Type 1414 high-definition film, SO-217 high-definition fine-grain film, and a series of films called "mono-cubic dispersed" or "monodispersed,", on which silver-halide crystals were very uniform in size and shape, providing significantly improved film speed and resolution. SO-315 contained silver-halide crystals of the order of 1,550 angstrom units in dimension, in SO-312 the size was reduced to 1,200, and in SO-409 to 900 angstrom units.

Kodak's technical data for Type 3404 quotes a resolving power of 50 to 100 line pairs per mm. Hence with the lowest resolution film, KH-8B could have achieved a resolution as good as 30 to 60 cm (1 to 2 ft). Using a film with a resolution equivalent to Kodak's Type 3414 AERECON High Altitude Film with a resolving power of 320 to 630 line pairs per mm would have enabled KH-8B to sample a ground resolution of 5 to 10 cm (2 to 4"), i.e. in the same order as the best resolution of 2.3"(?) Dwayne heard about.
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