The Countdown Clock is one of the most watched timepieces in the world, and our Live Launch Coverage is the only place online to get up-to-the-minute information during a countdown. On this page we explain how to understand and follow along with our launch coverage.
Follow along with our Live Countdown Coverage
As each milestone is reached, we will activate the appropriate link, indicated by a green star (). Links already activated will be marked with a brown star ().
"T" stands for scheduled liftoff time, "-" stands for minus, "H" stands for hours, "M" stands for minutes and "S" stands for seconds.
In the example below, the T-3 Hours & Counting milestone has been passed and the link has been activated. The T-20 Minutes and Holding milestone is the most recent page to be activated.
Please note that
timelines are projected and subject to change at any time during the
Countdown Event Guide
If the countdown clock reads T-26 hours and counting, that doesn't mean the Shuttle will launch in 26 hours. During every 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 Shuttle team
uses these 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.
Here are the key events that take place at each milestone after the countdown begins. Event lengths are approximate and subject to change.
T-43 hours and counting - Start Countdown Clock
T-27 hours & holding
T-27 hours & counting
T-19 hours & holding
T-19 hours & counting
T-11 hours & holding
T-11 hours & counting
T-6 hours & holding
T-6 hours & counting
T-3 hours & holding
T-3 hours & counting
T-20 minutes & holding
T-20 minutes & counting
T-9 minutes & holding
T-9 minutes & counting
T-0 - Liftoff!
|Page Last Revised||Page & Curator Information|
|April 3, 2002||Online
coverage by: Dennis Armstrong (NASA), Anna Heiney (IDI)
Web Development: Lynda Warnock & Debbie Barton (FDC)
Video Production: Chris Chamberland (Photobition)
Countdown Clock by: Jim Fitzgerald (FDC)
NASA Official: Dennis Armstrong (Dennis.Armstrongemail@example.com)
A Service of the NASA/Kennedy Space Center
Roy D. Bridges, Director