Brain Surgery In Space

The mission:

The launch:

The backup: Endeavour ready for rescue mission.

The idea of a standby rescue spacecraft grew out of the 2003 Columbia disaster, in which that shuttle disintegrated over Texas during re-entry into the Earth's atmosphere. That happened because of damage sustained during launch. But in Hubble's orbit, NASA has estimated there's also a 1-in-221 chance the shuttle could be struck and crippled by orbiting space debris.

All the previous missions since Columbia have gone to the International Space Station, where the crew of a damaged shuttle could take refuge there for months if need be until another shuttle was readied to retrieve them.

Article: USA Today, May 11th.