Oman York Conference(2001 in press)11/2/0 interest of lans. His 1982 book Human Visual Orientation", though out of print, remains the students best introduction to this subject. Over the subsequent two decades, he and his students built a set of unique stimulus devices in the basements of three buildings the now legendary rotating sphere, vection sled, mirrored bed and two tumbling rooms. They did a series of experiments on static and dynamic visual orientation which are landmarks in this field. Ian has al ways been fascinated by the orientation illusions reported by astronauts, and has done experiments in parabolic flight. In the early 1990s, he accepted my challenge to help me write the first NASa proposal for what has since become a series of continuing space flight investigations on human visual orientation on the Shuttle and the International Space Station employing virtual reality technology in space for the first time. both in the laboratory and in the field, Ian's discipline, intellect, curiosity, creativity, infectious scientific passion, and adaptability to Tex-Mex food inspired everyone including our astronauts. Some of the results from Neurolab-our first flight-are included here. Our laboratories also continue to collaborate in ground based research sponsored by the NAsA National Space Biomedical Research Institute .Human orientation problems In space Flight. Vision plays a critical role in maintaining spatial orientation in weightlessness. One of the most striking things about entering 0-G is that if the observers are in a windowless cabin, usually no one has any sensation of falling. Obviously"falling sensations are visually and cognitively mediated. If the observers make normal head movements, the visual surround seems quite stable. Oscillopsia(apparent motion of the visual environment), so common among patients who have inner ear disease, is only rarely reported in weightlessness. What can change -often dramatic fashion- is one's perception of static orientation with respect to the cabin and the environment beyond 2. 10-G Inversion Illusions. Ever since the second human orbital spaceflight by the late Gherman Titov in 1961, crewmembers in both the US and Russian space programs have described a bizarre sensation of feeling continuously inverted in O-G, even though in a familiar visually upright orientation in the cabin( Gazenko, 1964; Oman, et al, 1986)."The only way I can describe it', some say, "is that though I'm floating upright in the cabin in weightlessness both the spacecraft and I seem to somehow be flying upside down". Visual cues clearly play a role in the strength of the illusion, but in contrast with visual reorientation illusions( Sect. 2. 2) inversion illusions are relatively persistent, and continue after eyes are closed. Some report the illusion is stronger in the visually symmetrical mid-deck area of the Shuttle than when on the flight deck, or in the asymmetrical Spacelab module. Inversion illusion is sometimes reversible by belting or pulling yourself firmly into a seat, or looking at yourself in a mirror. The illusion is quite common among shuttle crewmembers in the first minutes of weightlessness, continuing or recurring for minutes to hours thereafter, but reports are rare after the second day in orbit. It is almost universal in parabolic flight among blindfolded volunteers entering weightlessness for the first time (Lackner, 1992). As detailed later, inversion illusion in 0-G has been attributed to the combined effects of gravitational unloading of the inner ear otolith organs, elevation of viscera, and to the sensations of facial fullness and nasal stuffiness caused by sitting with feet elevated prior to launch, launch accelerations, and 0-G fluid shiftOman York Conference (2001 in press) 11/2/01 Page 2 interest of Ian’s. His 1982 book “Human Visual Orientation”, though out of print, remains the student’s best introduction to this subject. Over the subsequent two decades, he and his students built a set of unique stimulus devices in the basements of three buildings: the now legendary rotating sphere, vection sled, mirrored bed and two tumbling rooms. They did a series of experiments on static and dynamic visual orientation which are landmarks in this field. Ian has always been fascinated by the orientation illusions reported by astronauts, and has done experiments in parabolic flight. In the early 1990s, he accepted my challenge to help me write the first NASA proposal for what has since become a series of continuing space flight investigations on human visual orientation on the Shuttle and the International Space Station, employing virtual reality technology in space for the first time. Both in the laboratory and in the field, Ian’s discipline, intellect, curiosity, creativity, infectious scientific passion, and adaptability to Tex-Mex food inspired everyone, including our astronauts. Some of the results from Neurolab - our first flight - are included here. Our laboratories also continue to collaborate in ground based research sponsored by the NASA National Space Biomedical Research Institute. 2. Human orientation problems in space flight. Vision plays a critical role in maintaining spatial orientation in weightlessness. One of the most striking things about entering 0-G is that if the observers are in a windowless cabin, usually no one has any sensation of falling. Obviously “falling” sensations are visually and cognitively mediated. If the observers make normal head movements, the visual surround seems quite stable. Oscillopsia (apparent motion of the visual environment), so common among patients who have inner ear disease, is only rarely reported in weightlessness. What can change – often in dramatic fashion – is one’s perception of static orientation with respect to the cabin and the environment beyond: 2.1 0-G Inversion Illusions. Ever since the second human orbital spaceflight by the late Gherman Titov in 1961, crewmembers in both the US and Russian space programs have described a bizarre sensation of feeling continuously inverted in 0-G, even though in a familiar “visually upright” orientation in the cabin (Gazenko, 1964; Oman, et al, 1986). “The only way I can describe it”, some say, “is that though I’m floating upright in the cabin in weightlessness, both the spacecraft and I seem to somehow be flying upside down ”. Visual cues clearly play a role in the strength of the illusion, but in contrast with visual reorientation illusions (Sect. 2.2), inversion illusions are relatively persistent, and continue after eyes are closed. Some report the illusion is stronger in the visually symmetrical mid-deck area of the Shuttle than when on the flight deck, or in the asymmetrical Spacelab module. Inversion illusion is sometimes reversible by belting or pulling yourself firmly into a seat, or looking at yourself in a mirror. The illusion is quite common among shuttle crewmembers in the first minutes of weightlessness, continuing or recurring for minutes to hours thereafter, but reports are rare after the second day in orbit. It is almost universal in parabolic flight among blindfolded volunteers entering weightlessness for the first time (Lackner, 1992). As detailed later, inversion illusion in 0-G has been attributed to the combined effects of gravitational unloading of the inner ear otolith organs, elevation of viscera, and to the sensations of facial fullness and nasal stuffiness caused by sitting with feet elevated prior to launch, launch accelerations, and 0-G fluid shift