The launch of the STS-121 mission occurred from the Kennedy Space Center at 1837:55 UTC. The NORAD SSC number is 29251 and the international designator is 2006-028A.
Here is the latest two line element set for STS-121.
STS-121
1 29251U 06028A 06185.80348940 .00055600 12106-4 74006-5 0 17
2 29251 51.6297 97.2629 0057780 342.0046 193.3540 16.29698905 02
