Six teams of students are vying for the chance to build an experiment for a satellite that will launch in 2010.
The semi-finalists are now required to work up a final proposal for submission in August; an outright winner will be selected by judges in the Autumn.
The winning experiment is required to be about the size of a lunch box, weighing no more than 1kg.
More: http://news.bbc.co.uk/2/hi/science/nature/7358438.stm