An Ariane 5 rocket reaches the ELA-3 launch zone Thursday at the Guiana Space Center, the final port of call for the James Webb Space Telescope before it ascends into orbit. Credit: ESA/S. Corvaja
Teams in French Guiana positioned a European Ariane 5 rocket into its starting blocks Thursday, ready for liftoff Christmas morning with the nearly $10 billion James Webb Space Telescope, the most expensive science instrument ever to leave planet Earth.