Flowers continue mission control tradition

As it has for more than 20 years, the Shelton family has delivered a vase of roses to NASA's Mission Control Center at Johnson Space Center in Houston as a shuttle mission nears an end.

Six roses represent Discovery's crew, six represent the International Space Station's Expedition 26 crew, and a single white rose remembers astronauts who have lost their lives.

"To our good friends at mission control and the crews of STS-133 and Expedition 26: Thank you Discovery, the beautiful workhorse of the shuttle fleet," reads the note signed by Mark, Terry, MacKenzie and Kyle Shelton.

Here's some more background on the tradition started by the Sheltons, from outside Dallas. They first sent the flowers in 1988 on the mission that followed the Challenger disaster.

"The mission control team here of course appreciates these every single time," said Josh Byerly, a NASA TV commentator. "It always means quite a bit to us."