PERCEPTION OF SPATIAL ORIENTATION IN MICROGRAVITY

Experiments during space and parabolic flights have shown that human s patial orientation in microgravity differs to a significant extent fro m its performance on earth. Due to the missing reference of gravitatio nal force, unusual perceptual phenomena are observed, from inversion i llusions to errors of perceived motion and position with respect to th e spacecraft. This article gives an overview of results collected from space missions and parabolic flight campaigns, and proposes new lines of research about the perceptual phenomena of spatial orientation in microgravity. It is shown that most of the disorientation phenomena ca n be explained by the existence of an internal estimate of the gravita tional vertical. In microgravity it is still maintained, but incorrect ly updated, and thus alters the processing of sensory information in t he central nervous system. This in turn leads to the observed illusion s, and probably also facilitates space motion sickness. (C) 1998 Elsev ier Science B.V. All rights reserved.