space.com animation: Deep Space 1 Asteroid Flyby (394k)

With its technology tests almost complete, NASA's Deep Space 1 mission is about to undertake the closest encounter with an asteroid ever attempted. Engineers hope to fly the satellite within 10 miles of the newly named asteroid Braille. The rendezvous is scheduled for Thursday morning at 12:46 a.m. ET.

This flyby will allow final testing of AutoNav, which enables the spacecraft to use images of distant stars and asteroids within our Solar System to keep track of its location in space and to guide trajectory changes. Deep Space 1 has successfully completed tests of its 11 other new technologies.

"Deep Space 1's main purpose is to test advanced technologies for the benefit of future missions, so we view the flyby and its science return as a bonus," said Dr. Marc Rayman, Deep Space 1's chief mission engineer and deputy mission manager. "This ambitious encounter is a high-risk endeavor, and its success is by no means guaranteed. But should there be significant data return, the findings will be of great interest to the science community."

During the flyby, a spectrometer and imaging instrument will send back black-and-white photographs and images taken in infrared light, while a second instrument observes the three-dimensional distribution of ions and electrons, or plasma, in the area. Scientist hope to learn more about Braille's shape, size, surface composition, mineralogy and terrain.