Visual Search in the Space Environment

Abstract

Among the important tasks of an astronaut will be the visual search for other vehicles in a co-planar orbit for purposes of rendezvous. Human data for minimum visual acuity can be used to compute the maximum sighting distance using information about target size, background, luminance and target contrast. But this distance is valid only if the astronaut knows the exact location of the target satellite and can fixate on it with foveal vision. For a dynamic search situation it is more meaningful to compute a probability of sighting using additional data or assumptions about peripheral visual acuity, eye fixation frequency, search area, and target closure rate. A method is described for computing probability of sighting. An example is provided for application of the method to a search situation for the approximate situation of a space rendezvous with a target comparable to the NASA Gemini vehicle.

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