Live in Orbit: Tally Ho!

Astronauts on the International Space Station have shuttle Discovery locked in their sights.

"We're tally-ho on the shuttle," station commander Mike Fincke told flight controllers in Houston. "We've never seen such a beautiful sight. It's awesome."

"Very good. Very good news," the flight controller responded.

The shuttle is within 3,000 feet of the station and will close within 600 feet shortly after 4 p.m.

Then commander Lee Archambault will guide Discovery through a nine-minute backflip below the station, called the Rendezvous Pitch Maneuver.

Docking is on track for 5:12 p.m.

If you look closely at the picture at left, you can see the "S6," or Starboard 6, truss tucked in Discovery's payload bay.

The 13-mission's top goal is to install that $298-million truss segment on the end of the station's backbone. It's the 11th and final piece, and the last major station component still to be installed that was built in the U.S.

The truss holds the final set of solar array wings, which will complete the station's power supply.