Vision Research: Flying and Space Travel; Proceedings of Spring Meeting, 1964. Edited by Milton a. Whitcomb and William Benson (1968) / Chapter Skim
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VISION IN SPACE TRAVEL
VISION IN SPACE TRAVEL
Pages 3-84
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Sensory Intelligence Laboratory The University of Michigan It is of the utmost importance at the present time to design laboratory experiments useful in describing human behavior so that data relevant to the problems of U.S. space and military efforts may be obtained.
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is the counterpart of an observer in a visual experiment, and his interpretation of the experimental results is the observer's responses. In other words, when one performs a visual experiment, he is studying processes very similar to those he is performing in conducting the experiment.
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associated probability. The entropy of this set is the uncertainty of knowledge, prior to the experiment regarding which hypothesis is "true." One of the hypotheses in the set is presumed to be selected by nature for transmission.
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cution, and the interpretation of experiments. At the outset, the first statement indicates that complete disbelief in an hypothesis eliminates that hypothesis from consideration.
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regard to scientific or practical application, depends on the choice of a useful set of hypotheses with which to work. Further examination indicates the required content of the data.
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Consider the possibility of computing the number of observations necessary to reduce the entropy of a parameter coefficient from one value to another. The terms are defined as follows: a j = initial variance, ff2Q = variance associated with an observation, cj2 = variance of estimate following the experiment.
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The discussion of size of experiment to this point has been entirely in terms of estimating a single coefficient. If one tries to extend this to a set of W orthogonal coefficients, then a bandwidth term is introduced, and each of the entropy terms must then be multiplied by W, as must the size of the experiment.
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the internal noise and uncertainty in amplitude memory. The memory requirements for frequency, phase, starting time, and duration were removed by superimposing the signal to be detected on a pedestal -- a segment of sinusoid of the same frequency, phase, starting time, and duration as the signal.
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The practical problem is that it is highly desirable to describe behavior which might exist in certain field situations. Laboratory experiments designed to meet this goal should, then, fall in the same descriptive space as the practical situations.
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space as some tasks of practical interest where the cost of not observing is prohibitively expensive. Indeed, if it were not, there would be no interest in describing behavior in such situations.
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SUMMARY An explanation of the establishment of criteria for the design of laboratory experiments useful to field situations has been presented. The first step, that of describing the current state of knowledge, is accomplished by stating a set of possible hypotheses to which an associated probability or degree of belief is assigned.
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illustrated by an experiment on memory in psychophysical tasks, and the problem of the interpretation of data obtained from experiments on vigilance was discussed. In conclusion, it is again emphasized that the most important factor is a precise statement of the problem to be studied.
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Visual parameters presently tested do not necessarily have a bearing on the visual functions required and, indeed, the visual parameters may change during the dynamic or stressful performance situation. For example, in the area of auto driving static visual tests fail completely in adequately selecting night vision capability.
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Also, one eye may be dark-adapted for cockpit visual tasks while the other eye could be light-adapted for visual search of the sky. The authors are not so naive as to believe that this notion will be accepted as practical, but it does serve to emphasize the principle that perfection in the different visual parameters, as measured under static conditions, is not to be equated to visual unstressability nor to visual fitness.
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It is hoped that those responsible for visual fitness criteria and selection standards will recognize the lessons from the past: static tests are insufficient to evaluate the dynamic stressful performance situation. Finally, the importance of measuring what one should rather than what one can is again emphasized.
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Langmuir and Westendorp (1931) recommended, on the basis of experimental work, that a flashing light should have 10 times the illuminance of a threshold flashing light to ensure detection by the second or third flash.
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The light flashes were produced by a telescopic projection system that rotated about its axis at the rate of T of arc/sec. The light flash was produced by a cam-actuated switch which pulsed a tungsten source.
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The light source therefore had an apparent intensity of 9.35x 10"^ candles. Since the target was matte and the light patch subtended a visual angle of between 2- and 3- of arc, the inverse square law of illumination is applicable and is accurate to about 2 per cent.
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EXPERIMENTAL CONDITIONS A total of 130 experimentally naive subjects were utilized. Normally, the subjects were run in subgroups of 19, which were serially labeled 1 through 7.
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The null hypothesis was sustained between conditions I and II, but rejected between conditions I and III, and between conditions II and III. It was hypothesized that there was no difference between the proportion of flashes seen under the three experimental conditions.
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The significance of difference was tested by means of correlated x that was corrected for continuity. The null hypothesis was sustained between trials 1 and 2 and between trials 2 and 4, but it was rejected for trials 1 and 3, and trials 1 and 4.
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TABLE 5. Summary and Analysis of Number of Subjects DetectingFlashes for the First Four Trials Number of Subjects Detecting Flashes 0.13 kmc 0.935 kmc Trial 1 Massed 1 Distributed 1 Reported 4 12 Not reported 15 7 Total 19 19 Trial 2 Distributed 1 Massed2 Reported 7 15 Not reported 12 4 Total 19 19 Trial 3 Massed 1 Distributed2 Reported 11 18 Not reported 8 1 Total 19 19 Trial 4 Distributed 2 Massed Reported 11 17 Not reported 8 2 Total 19 19 Statistical Comparison of Trial 1 with Trials 2, 3, and 4 and Trial 2 with Trial 4 Trial 1 0.130 kmc Trial 4 Trial 2 2.00 3.12 Trial 3 7.11*
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* Null hypothesis rejected at 0.00003 level of confidence.
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on the number of flashes reported, and this hypothesis was tested by means of a statistic for the testing of proportions obtained from large populations of subjects. It may be seen, for the 0.13kmc flash, that the null hypothesis was rejected in the case of trials 1 and 2, trials 1 and 3, trials 1 and 4, and trials 2 and 4.
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The present study indicates that only one-half to two-thirds of the subjects made their first detection by the third flash. This is inferior to the performance predicted by Langmuir and Westendorp when they stated that one could assure detection by the second or third flash, particularly, when it is considered that between 40 and 80 per cent of the subjects were incapable of making a detection.
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E The effect of flash frequency on the apparent intensity of flashing lights having constant flash duration.
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LANGLEY RESEARCH CENTER SIMULATORS AND STUDIES RELATED TO SPACE RENDEZVOUS AND DOCKING Jack E Pennington NASA Langley Research Center The best way of investigating many piloting tasks is through the use of simulators that duplicate the mission as closely as possible.
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Two high-intensity flashing lights mounted on the Agena will enable it to be detected by the Gemini pilots at ranges up to 20 miles. However, such a flashing light can be used only at night, and the power requirements are relatively high.
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simulation work were important in defining man's part in the Gemini rendezvous, and also strongly influenced the adoption of the Lunar Orbit Rendezvous technique for the Apollo mission. Studies of rendezvous with low thrust levels, such as reported in Beasley (1963)
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3) utilized two circular light spots projected on a cylindrical screen to simulate remote assembly of two objects, such as fuel tanks, controlled from a spacecraft a short distance away.
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-SMM cute Moea urn met |
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only the cone was illuminated, rather than the entire body of the target. Second, the nose of the Gemini was not lit, so the pilot saw the indexing bar only when it was silhouetted against the illuminated target cone.
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6. In addition to the docking cone and latching mechanism, it contains two high-intensity flashing lights mounted at about 11 o'clock and 5 o'clock on the Adapter.
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were placed at 9 o'clock and 3 o'clock they would not be seen by either astronaut when docked. As mentioned earlier, the night flights had shown a need for a visual-aid technique that could increase the docking accuracy.
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Flat black curtains to keep ambient light out of the darkened hangar are used with filters over the capsule windows. Thus, it is necessary to consider not only the pilot's visual capabilities, but also the simulator's visual characteristics.
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Preferably, guidance for the application of these procedures should be independent of complex automatic equipment. Many task areas of Project Apollo exist for which simple manual procedures have not been developed, for example, midcourse navigation, orbit establishment, lunar landing, etc.
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1. They include earth entry, rendezvous, docking, midcourse navigation, orbit ephemeris determination, lunar orbit establishment, powered lunar descent, hover and translation, and lunar launch.
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noted that the angle between the excursion-module thrust vector and the line of sight to the orbiting spacecraft remained very nearly constant during the powered descent phase (see Fig.
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In other words, it appears that the astronaut could navigate by aiming his vehicle, using a scribed windshield or some other simple sighting device, possibly as shown in Fig.
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meats of such parameters as rotation of a line-of-sight, altitude, altitude rate.
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The size, scale factors, and altitude range of each model are shown in Table 1.
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CONCLUDING REMARKS In conclusion, the Langley Research Center has been examining, through analytical and simulation studies, simple guidance techniques for pilot control of various tasks associated with the lunar mission. These simplified techniques and pilot utilization should increase the reliability of Project Apollo and other manned space missions.
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REFERENCES Barker, L
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. In this study the term visual masking refers to the gradual reduction of correct responses as to the orientation of a patterned test stimulus as the temporal interval between the test stimulus and a succeeding brighter masking stimulus is decreased.
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2. The optical system consists mainly of a monocular Maxwellian-view optical system, with Sylvania R1131C glow modulators as light sources, and a red fixation-light source.
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. As seen by the subject, the blanking flash was superimposed upon the test flash in the open central area of the fixation pattern.
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A, B, and C are equal area test flash patterns, D is fixation pattern, and E is blanking flash pattern. White areas represent lighted portion of pattern as seen by subject.
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From Fig. 4, it can be seen that visual masking decreases as test-flash luminance is increased or as the interval between the test flashes and blank100 (MILLISECONDS)
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6. Time between test- and blanking-flash onsets as function of test-flash luminance and teststimulus patterns at constant 50 per cent correct level.
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7. If one imagines an electrode implanted in the brain to measure evoked potential latencies at the point where visual masking occurs, TF refers to the time the test flash was initiated, and TTF to the latent period after which an evoked potential (TFe)
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This would indicate that the neural interaction between test- and blankingflash evoked potentials is dependent on the form of the test stimulus. This could be expected because slightly different retinal elements are activated by the different test patterns, even though the over-all test pattern areas are equated.
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Accordingly, it would take longer to perceive a visual stimulus than the figures would indicate. There is also an unproved assumption about the relationship between evoked potentials and the phenomenon of visual masking when any recorded value of evoked potential latency is used.
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Lindsley, D
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Lampkin NASA Ames Research Center Moffett Field The Ames Research Center is studying the role of the crew in the navigation, guidance, and control for the midcourse phase of manned space missions. In pursuit of these investigations, a lunar midcourse navigation and guidance simulator has been constructed at Ames.
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. Unfortunately, the direct optical planetarium is subject to optical parallax due to the finite distance between the light source and the viewer.
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For the moment manual sextant sighting performance is being investigated as a possible minimum manual system for gathering navigational data. Later, this task will be integrated with the larger task of inputting the data to the on-board computer and, ultimately, with the broader task 64
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Both of these methods involve considerable mathematical computation, but each, in most cases, depends first on the seemingly simple task of measuring an angle with an optical sighting device. In marine and air navigation, the accuracy of the celestial fix depends largely on the measurement of angular altitude of the body of interest above the natural sea horizon or the bubble horizon.
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. Obviously, these are not highly accurate instruments in terms of error tolerances for space navigation.
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The interest was not, however, in the ascertainment of absolute sighting performance; but rather the determination of whether there was a difference in performance between the hand-he Id and the gimbaled sextant, and also whether oscillatory motion affected performance to any great extent. Accordingly, an arbitrary limit-cycle function was programmed on an analog computer to drive the cab using the cold gas jet system.
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One of the major differences is due to the use with modern bubble sextants of manual or automatic integrating devices that allow for the averaging of a continuous sighting over a minute or two of time. The marine sextant is a single-shot device and is so used in sea navigation.
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These are general statements because they result from an initial judgment of what is important in sighting performance as identified in the simulated task environment. The opportunity to make these judgments is provided by the midcourse navigation and guidance simulator.
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D-2238. United States Navy Department, Space navigation handbook.
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Gordon Cooper. During certain of the 22 orbits, Major Cooper reported having seen objects on the surface of the earth that must necessarily have subtended very small visual angles from the capsule altitude.
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It should be emphasized at the outset that Major Cooper is a remarkably careful observer; he is meticulous in differentiating fact from inference. Not only does he have excellent visual acuity, as measured clinically, but he has had a tremendous amount of experience in the reconnaissance of angularly small, distant objects.
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They combined measured atmospheric transmission data, known visualperformance capabilities, and both measured and assumed properties of the objects purportedly seen. The estimated inherent characteristics of the reported objects were arrived at by some rather interesting sleuthing.
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Case II During a pass over the high Tibetan plateau (ground elevation 16,000 ft) Major Cooper reported seeing, on an east-west road, a dust cloud blown by a "wind out of the south" which he inferred to be a "stiff breeze" from the angle it appeared to assume relative to the ground.
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This probability increased markedly with size, so that, for example, a vertical wall having twice the area, i.e., 276 sq ft, would generate an optical signal of detection probability greater than 0.90. Some detective work led to the discovery that the smoke issuing from these structures may have produced a positive contrast sufficient to be seen with a probability of 0.50, for the usual local fuel in these timberless regions is yak dung, which yields a dense, light smoke.
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means perfect vision"? Major Cooper's Snellen acuity happens to be 20712, or 0.60 min of arc, although, as is indicated below, this value is merely suggestive of his superior vision and does not represent a limiting value of visual resolution.
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One variety of visual acuity comes from tests in which the observer is required to detect the presence of a discontinuity in an extended line. This measure, called "vernier acuity" from its resemblence to the visual task required in the reading of vernier instrument scales, is analogous to the situation in which an extended line is suddenly displaced by some small angular amount.
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Finally, reconstructing the event merely indicates the possibility of the sightings, and in no wise proves them to have been made. An opportunity to perform controlled experiments during future space flights is, therefore, anticipated with great enthusiasm.
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The astronauts involved in missions GT-5 and GT-6, and/or GT-7 will be required to measure their own visual acuity during the mission with the aid of an in-flight vision tester, which will be provided by the Visibility Laboratory of the University of California, San Diego. This task will involve the use of the tester by each man once a day throughout the flight.
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This photometer will be aligned with a small, circular light trap which will be mounted outside the window on the hatch immediately in front of the photometer, about 9 inches in front of the window. The output from this photometer will be telemetered through the high-level dumped telemetry system.
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All of this information will be used to determine the nature of the optical signal available to the astronaut, and the Laboratory will then correlate this with his visual performance. A National Aeronautics and Space Administration van will be outfitted by the Visibility Laboratory and set up in Houston to measure the visual capabilities of the astronauts and to train them in the use of the in-flight vision tester.
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FLASH BLINDNESS John L Brown, Chairman
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