Essay About Human Visual Hardware And Seconds Of Arc

The Human Eye in Space
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Human visual hardware is a result of a billion years
of evolution within the earths atmosphere where
light is scattered by molecules of air, moisture,
particular matter etc. However as we ascend into
our atmosphere with decrease density, light
distribution is changed resulting in our visual
hardware receiving visual data in different format.
Some Aspects to Consider: 1. Visual acuity is the
degree to which the details and contours of
objects are perceived. Visual acuity is usually
defined in terms of minimum separable.Large
variety of factors influence this complex
phenomenon which includes : # Optical factors-
state of the image forming mechanisms of the eye.
# Retinal factors such as the state of the cones. #
Stimulus factors such as illumination, brightness of
the stimulus, contrast between the stimulus and
background, length of time exposed to the
stimulus. * Minimum separable: shortest distance
by which two lines can be separated and still be
perceived as two lines. “During the day, the earth
has a predominantly bluish cast.. I could detect
individual houses and streets in the low humidity
and cloudless areas such as the Himalaya
mountain area…. I saw a steam locomotive by
seeing the smoke first….. I also saw the wake of a
boat on a large river in the Burma-India area…
and a bright orange light from the British oil
refinery to the south of the city (Perth,Australia.)”
The above observation was made by Gordon
Cooper in Faith 7 [1963] and which generated
much skepticism in the light of the thesis by
Muckler and Narvan “Visual Surveillance and
Reconnaissance from space vehicles” in which
they determined that a visual angle of ten minutes
was the operational minimum, and that the
minimum resolvable object length [M.R.O.L] at an
altitude of 113 miles would be 1730 ft. This
limitation of acuity was revised the next year to 0.5
seconds of arc for an extended contrasting line
and 15 seconds of arc for minimum separation of
two points sharply contrasting with the
background. Orbiting at 237 miles in the skylab it
was possible to see the entire east coast [Canada
to Florida Keys] and resolve details of a 500 feet
long bridge based on inference. Of Interest is the
fact that even though the mechanical eye [camera
systems] can resolve objects greater than fifty
times better than the human eye, without the
human ability to infer, interpretation of the data is
meaningless. Conclusion: Visual acuity in space
exceeds that of earth norm when objects with
linear extension such as roads, airfields, wake of
ships etc. 2. Stereoscopic vision: the perception of
two images as one by means of fusing the
impressions on both retinas. In space one has to
deal with a poverty of reference points. For
hardware evolved in a reference oriented
paradigm, this possess a grave