S99-05679 (24 May 1999) --- Astronauts Claude Nicollier (seated), representing the European Space Agency (ESA), and John M. Grunsfeld use virtual reality hardware to rehearse some of their duties for the upcoming STS-103 mission, NASA's third servicing visit to the Earth-orbiting Hubble Space Telescope (HST). The two mission specialists will be joined by five other astronauts, including a second ESA representative, for the STS-103 mission, scheduled for autumn of this year.