SUBMITTED BY ARTHUR N1ORC - AMSAT A/C #31468

LAUNCH COVERAGE NASA's Launch Blog - Mission STS-116 http://www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts116/launch/laun...

*NASA's launch blog will begin live coverage on Dec. 7, 2006 at 3:30 p.m. EST. *

*Did you know?* If the countdown clock reads T-26 hours and counting, that doesn't mean the space shuttle will launch in 26 hours. During every space shuttle countdown, there are several times when the clock is temporarily stopped. These periods are called "built-in holds," and they vary in length from as little as 9 minutes to as long as several hours. For this reason, hold times must be taken into consideration when watching the countdown clock.

The space shuttle team uses built-in holds to synchronize with other countdown clocks, monitor weather events, make final adjustments to the launch time, and check all systems before proceeding.

During the countdown the liquid oxygen vent on the external tank is opened to allow the super-cold liquid oxygen to boil off, thus preventing over pressurization while the tank remains near its full level.

Once the space shuttle's on board computers start their terminal launch sequence, any problem after that point will require calling a "hold" and the countdown recycled to T minus 20 minutes.