Welcome to the STS-120 Launch Blog
Relive the countdown to space shuttle Discovery's successful liftoff on Oct. 23, 2007, beginning mission STS-120 to the International Space Station.
Video highlights of the STS-120 countdown are selected from televised coverage provided by NASA TV. + View Videos
Note: All times are given in Eastern (EDT) unless otherwise noted.
Thanks for following space shuttle Discovery's countdown with NASA's Launch Blog. Check the shuttle section
of www.nasa.gov each day for the latest news, and be sure to join us back here on landing day
for complete coverage of Discovery's return to Earth.
11:50 a.m. - The STS-120 crew is in orbit aboard space shuttle Discovery! This beautiful liftoff was just the beginning of this exciting mission, which will involve the shuttle and station crews working together to continue constructing the International Space Station.
11:48 a.m. - Right on time, we have main engine cutoff and external tank separation as Discovery reaches space.
11:40 a.m. - The solid rocket boosters have separated. Discovery climbs toward space, and all is going well with the flight as the shuttle's three main engines power the vehicle through Earth's atmosphere.
11:38 a.m. - Three... two... one... and liftoff of space shuttle Discovery carrying the seven STS-120 astronauts! The shuttle has cleared the launch tower, beginning its mission to bring Harmony to the International Space Station.
The shuttle rolls into a head-down position as it climbs skyward. Discovery's three main engines throttle down to about 72 percent around 30 seconds after liftoff. One minute after launch, the engines throttle up again to 104 percent, bringing the vehicle to the peak of aerodynamic pressure called "max Q."
Two minutes into flight, the twin solid rocket boosters will burn out and separate, falling back to Earth toward the Atlantic Ocean, where the booster recovery ships, Freedom Star and Liberty Star, are stationed to retrieve them.
11:33 a.m. - All systems remain "go" with the launch of Discovery on mission STS-120 just minutes away.
11:29 a.m. - Coming out of the hold, the countdown clock is at T-9 and counting. Liftoff of space shuttle Discovery is just minutes away now as the automatic ground launch sequencer starts. During these final minutes in the countdown, a number of events take place to ready the shuttle for launch. The crew access arm retracts, auxiliary power units start and the gaseous oxygen vent arm pulls back.
11:26 a.m. - The final poll by Launch Director Mike Leinbach gives Discovery "go" for launch!
11:24 a.m. - Mission Management Team Chairman LeRoy Cain and NASA Test Director Jeff Spaulding polled both their teams and Discovery is "go" for launch.
11:22 a.m. - After re-examining an area of ice on the external tank's liquid hydrogen umbilical, it's been determined that it is not a problem on liftoff today.
11:20 a.m. - Before this hold ends at 11:29 a.m., the final polls will be conducted, leading to a liftoff at 11:38 a.m.
11:09 a.m. - Still in the built-in hold, the ice issue continues under discussion and the weather is looking favorable. It's a fact:
The STS-120 mission will be the first spaceflight for Pilot George Zamka and Mission Specialists Doug Wheelock and Paolo Nespoli.
10:44 a.m. - The countdown clock now stands at T-9 and holding. This is the final built-in hold in today's countdown. During this time, the launch director, mission management team and NASA test director conduct their final "go/no-go" polls.
10:33 a.m. - Coming out of the hold, the clock is once again moving. There will be one final hold at T-9 minutes. Discovery's onboard computers are being transitioned to launch configuration and fuel cell thermal conditioning has begun. The shuttle cabin vent valves are being closed.
10:23 a.m. - The countdown clock now stands at T-20 and holding. This is a built-in hold lasting for 10 minutes. During this time, the NASA test director conducts final launch team briefings.
10:21 a.m. - As the White Room is closed out, the countdown is approaching the next built-in hold that occurs at the T-20 minute mark. It's a fact:
Space shuttle Discovery will weigh 4,524,141 pounds at liftoff. That's roughly equivalent to the takeoff weight of five Boeing 747-400ER aircraft.
10:04 a.m. - The Closeout Crew has sealed the hatch and is performing hatch seal and cabin leak checks before departing the launch pad area. Members of the Final Inspection Team have reached the pad for a further review of an area of ice that they previously observed.
9:54 a.m. - Launch managers are sending the Final Inspection Team back to the launch pad to take another look at the ice that has been observed. The team will be able to communicate with the Launch Control Center about the issue and send back pictures of the area of concern.
9:40 a.m. - Launch managers are looking at a report from the Final Inspection Team about an area of "clear ice" near the liquid hydrogen umbilical on the external tank. It is described as four inches long and about a half inch in diameter. Managers will continue to evaluate the situation.
Weather conditions continue to be closely watched. Although observed conditions appear to be "go" for launch, the ocean breeze is forecast to roll in at 11 a.m. and could bring with it some rain and clouds.
9:28 a.m. - With all the STS-120 astronauts on board space shuttle Discovery, the Closeout Crew members have been given the "go" to begin closing out the crew cabin. Once the hatch is closed, they will perform hatch seal and cabin leak checks before departing the launch pad area, leaving the astronauts alone to await liftoff.
9:18 a.m. - Wheelock, Tani and Wilson are now onboard Discovery and the technicians continue to help the crew strap in for launch. It's a fact:
The STS-120 mission will mark the first time females have been in command of both the space shuttle and the International Space Station at the same time. Space shuttle Discovery is being commanded by Pam Melroy, and Peggy Whitson is currently serving as the station's commander.
8:40 a.m. - Next to board Discovery was Mission Specialist Paolo Nespoli, who represents the European Space Agency. He was followed by Pilot George Zamka, then Mission Specialist Scott Parazynski. Mission Specialists Doug Wheelock, Dan Tani and Stephanie Wilson will board next. Tani will remain on the International Space Station, replacing Clay Anderson who will return to Earth with the STS-120 crew.
8:18 a.m. - The crew members are beginning to board Discovery, with Commander Pam Melroy the first to enter the shuttle and strap in. As a standard part of the boarding process, all the astronauts do a communication or "comm" check to verify that they are in two-way communication with both the launch team at Kennedy and Mission Control in Houston.
8:08 a.m. - The astronauts have reached the foot of Launch Pad 39A where space shuttle Discovery waits to carry them on their mission to the International Space Station. They will ride the pad's elevator up to the 195-foot level where the White Room crew awaits their arrival.
8:00 a.m. - The Astrovan has reached the Launch Complex 39 area where it has paused near the Launch Control Center so that Ellen Ochoa, director of Flight Crew Operations at Johnson Space Center, can disembark. She is accompanied by astronaut Brent Jett, commander of STS-115, who is set to take over Ochoa's position after this mission. The vehicle also stopped briefly to drop off Steve Lindsey, chief of the Astronaut Corps, who will take off from the Shuttle Landing Facility in one of the Shuttle Training Aircraft to monitor the weather conditions. Ochoa and Lindsey accompanied the crew members as they readied for flight in Crew Quarters.
7:48 a.m. - Smiling and waving to gathered space center workers, the STS-120 astronauts are making their way out of the Operations and Checkout Building where the Crew Quarters are located. They are walking the short distance to the silver Astrovan that will carry them on the 20-minute ride to the launch pad.
7:45 a.m. - The Final Inspection Team has finished its detailed check of the vehicle and launch pad and is now heading back to the Launch Control Center to give their report.
7:43 a.m. - Coming to the end of the two hour and 30 minute built-in hold, at T-3 hours the countdown clock is once again ticking down toward today's liftoff. There are two more built-in holds in today's countdown, coming at the T-20 and T-9 minute marks.
7:30 a.m. - Launch day dawns at Launch Pad 39A, and space shuttle Discovery is silhouetted against the sky as the sun rises over the Atlantic Ocean. Inside the White Room, preparations continue in advance of the astronauts' arrival at the pad.
7:25 a.m. - The Final Inspection Team members are working on the mobile launch platform and can be seen moving around the boosters' aft skirts and the tail of space shuttle Discovery.
Back in Crew Quarters, the STS-120 astronauts just received their weather briefing, and two trans-Atlantic abort sites are available today: Spain's Moron and Istres, France, with Moron as the prime site.
7:15 a.m. - Stationed about 140 miles offshore in the Atlantic Ocean, NASA's booster recovery ships Freedom Star and Liberty Star stand ready to retrieve the two solid rocket boosters that will tumble into the ocean once they separate from the shuttle. The boosters are towed back to shore where they are refurbished and reused for future shuttle launches.
7:00 a.m. - Inside the Crew Quarters in the Operations and Checkout Building, the astronauts are getting ready to put on their pressurized launch-and-entry suits before departing for Launch Pad 39A.
6:55 a.m. - Kathy Winters, launch weather officer, has advised Launch Director Mike Leinbach that weather is currently "green" for launch.
Members of the Orbiter Closeout Crew are inside the White Room making final preparations for the astronauts to climb aboard Discovery, which should begin at about 8:18 this morning. The team is joined by today's Astronaut Support Personnel, led by astronaut Jose Hernandez. These astronauts assist in advance of the crew's arrival at the pad, and help them as they board Discovery.
6:35 a.m. - As members of the Final Inspection Team (also known as the Ice Team) finish the top-to-bottom examination of the shuttle and launch pad, they are using a new system that allows them to send images via a laptop computer back to the launch managers in the Launch Control Center.
6:30 a.m. - Good morning. The countdown to the launch of space shuttle Discovery is in the T-3 hour built-in hold and scheduled to resume at 7:43 a.m. Filling of Discovery's giant orange external tank with 500,000 gallons of liquid oxygen and liquid hydrogen was completed earlier, and both propellants will remain in stable replenish mode, meaning they are kept full until the final minutes of today's countdown.
In Crew Quarters, the seven astronauts are scheduled to receive a weather briefing within the hour before they begin suiting up. The astronauts will be assisted as they put on the familiar orange launch-and-entry suits before boarding the Astrovan for the trip to the launch pad, where they will take their seats aboard Discovery.
Launch remains on schedule for 11:38 a.m. and weather continues to be the only issue, with a 60-percent chance that it will prohibit liftoff today. Keeping track of today's weather conditions from the Shuttle Training Aircraft is astronaut Steve Lindsey, chief of the Astronaut Corps. There is a 10-minute launch window available, with the scheduled launch time occurring in the middle of that window.
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