The Human Eye in Space :: essays research papers

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.