Franklin Chang-Diaz performing retinal photography on fellow mission specialist Ellen Baker during Shuttle Atlantis' STS-34 mission. Photographs taken in space were compared with those taken on Earth before the flight to detect any swelling in the blood vessels of the retina. This may be caused by oedema, a shift of body fluids as a result of the microgravity environment in orbit. Although undertaking many experiments, the primary task of the crew was to deploy the Galileo Jupiter exploration probe. Launched on 18th October 1989, Atlantis made 80 orbits before returning safely on 23rd October 1989.