Astronaut performing a lung function test. US astronaut Kathryn P. Hire involved in a sophisticated lung function test in the Neurolab on space shuttle Columbia during mission STS-90 (17th April - 3rd May 1998). The test was part of a sleep/respiratory study, undertaken in the Neurolab (an onboard laboratory designed to test how human bodies adapt to microgravity conditions). The study was prompted by the sleep difficulties experienced by astronauts while in space. Photographed on 20th April 1998.