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Katherine Trinidad
Headquarters, Washington

Bruce Buckingham
Kennedy Space Center, Fla.

RELEASE : 38-06
NASA Space Shuttle Discovery's Launch Countdown Begins June 28
NASA will begin the countdown for the launch of Space Shuttle Discovery at 5 p.m. EDT June 28, at the T-43 hour point. The countdown includes nearly 28 hours of built-in hold time leading to a preferred launch time at about 3:49 p.m. EDT on July 1. The launch window extends for about five minutes.

The Kennedy Space Center launch team will conduct the countdown from the newly renovated Firing Room 4 of the Launch Control Center.

This mission is the 115th shuttle flight and the 18th U.S. flight to the International Space Station. Discovery's mission, designated STS-121, is scheduled to last about 12 days with a planned landing at about 10:45 a.m. EDT on July 13 at Kennedy. The STS-121 crew will test new equipment and procedures to improve shuttle safety, as well as deliver supplies and make repairs to the International Space Station.

Discovery rolled into Kennedy's Orbiter Processing Facility on Aug. 22 last year, after returning from its last mission, STS-114. On May 12, the shuttle rolled out of the facility and into the Vehicle Assembly Building, where it was mated to its redesigned external fuel tank and solid rocket boosters. The space shuttle stack was transferred to Launch Pad 39B on May 19.

The STS-121 crew includes Commander Steven Lindsey, Pilot Mark Kelly and mission specialists Michael Fossum, Lisa Nowak, Stephanie Wilson, Piers Sellers and Thomas Reiter, an astronaut with the European Space Agency. Reiter will join the Expedition 13 crew on the station as flight engineer 2 and will become the first long-duration crew member who is not American or Russian.

The STS-121 mission is the second mission in the Return to Flight sequence. Payloads aboard Discovery include a new control and life-support system that uses water to generate enough oxygen for up to six people. Science experiments requiring data collection from crew members will help understand space motion sickness, latent virus reactivation and shedding, renal stone formation and insomnia.

In the payload bay, the multi-purpose logistics module Leonardo, built by the Italian Space Agency, will carry more than two tons of hardware, equipment and supplies up to the station and return unneeded items back to Earth. This is Leonardo's fourth trip to the station.

During two planned spacewalks on the fifth and seventh days of the mission, Sellers and Fossum will test the 50-foot robotic arm boom extension as a work platform and also test techniques for inspecting and repairing the reinforced carbon-carbon segments that protect the shuttle's nose cone and wing leading edges. The spacewalkers will install spare parts for future use and replace the trailing umbilical system reel assembly for the station's mobile transporter, a rail car that travels along the station's truss.

*Televised events (times may vary slightly)
All times Eastern

Launch-3 Days (Wednesday, June 28)

Prepare for the start of the STS-121 launch countdown
Perform the call-to-stations (4:30 p.m.)
Countdown begins at the T-43 hour mark (5 p.m.)
Begin final vehicle and facility close-outs for launch
Check out backup flight systems
Review flight software stored in mass memory units and display systems
Load backup flight system software into Discovery's general-purpose computers

Launch-2 Days (Thursday, June 29)

Remove mid-deck and flight-deck platforms (1 a.m.)
Complete preparation to load power reactant storage and distribution system (4 a.m.)
Activate and test navigational systems (6 a.m.)
Flight deck preliminary inspections complete (9 a.m.)

Enter first built-in hold at T-27 hours for duration of 4 hours (9 a.m.)

Clear launch pad of all non-essential personnel
Perform test of the vehicle's pyrotechnic initiator controllers

Resume countdown (1 p.m.)

Begin operations to load cryogenic reactants into Discovery's fuel cell storage tanks (2:30 p.m.)

Enter 4-hour built-in hold at T-19 hours (9 p.m.)

Demate orbiter mid-body umbilical unit (9:30 p.m.)
Resume orbiter and ground support equipment closeouts

Launch-1 Day (Friday, June 30)

Resume countdown (1 a.m.)

Final preparations of shuttle's three main engines for main propellant tanking and flight (1 a.m.)
Begin filling pad sound suppression system water tank (2 a.m.)
Pad sound suppression system water tank filling complete (5 a.m.)
Close out the tail service masts on the mobile launcher platform

Enter planned hold at T-11 hours for 13 hours, 53 minutes (9 a.m.)

Begin star tracker functional checks (9:50 a.m.)
Activate orbiter's inertial measurement units
Activate the orbiter's communications systems
Install film in numerous cameras on the launch pad (10:55 a.m.)
Flight crew equipment late stow (2:50 p.m.)
Move Rotating Service Structure (RSS) to the park position (6:30 p.m.)
Perform ascent switch list
Fuel cell flow-through purge complete

Resume countdown at T-11 hours (10:53 p.m.)

Launch Day (Saturday, July 1)

Activate the orbiter's fuel cells (12:02 a.m.)
Clear the blast danger area of all non-essential personnel
Switch Discovery's purge air to gaseous nitrogen (12:53 a.m.)

Enter planned 2-hour built-in hold at the T-6 hour mark (3:53 a.m.)

Launch team verifies no violations of launch commit criteria prior to cryogenic loading of the external tank
Clear pad of all personnel

Resume countdown (5:53 a.m.)

Chill down of propellant transfer lines (5:53 a.m.)
Begin loading the external tank with about 500,000 gallons of cryogenic propellants (about 6:03 a.m.)
Complete filling the external tank with its flight load of liquid hydrogen and liquid oxygen propellants (about 8:53 a.m.)
Final Inspection Team proceed to launch pad

Enter planned 3-hour built-in hold at T-3 hours (8:53 a.m.)

Perform inertial measurement unit preflight calibration
Align Merritt Island Launch Area (MILA) tracking antennas
Perform open loop test with Eastern Range

Resume countdown at T-3 hours (11:53 a.m.)

Crew departs Operations and Checkout Building for the pad (11:58 a.m.)
Complete closeout preparations in the white room
Check cockpit switch configurations
Flight crew begins entry into the orbiter (about 12:28 p.m.)
Astronauts perform air-to-ground voice checks with Launch and Mission Control
Begin to close Discovery's crew hatch (about 1:38 p.m.)
Begin Eastern Range final network open loop command checks
Perform hatch seal and cabin leak checks
Complete white room closeout
Closeout crew moves to fallback area
Primary ascent guidance data is transferred to the backup flight system

Enter planned 10-minute hold at T-20 minutes (2:33 p.m.)

NASA test director conducts final launch team briefings
Complete inertial measurement unit preflight alignments

Resume countdown at T-20 minutes (2:43 p.m.)

Transition the orbiter's onboard computers to launch configuration
Start fuel cell thermal conditioning
Close orbiter cabin vent valves
Transition backup flight system to launch configuration

Enter estimated 40-minute hold at T-9 minutes (2:54 p.m.)

Launch director, mission management team and NASA test director conduct final polls for go/no go to launch

Resume countdown at T-9 minutes (about 3:40 p.m.)

Start automatic ground launch sequencer (T-9:00 minutes)
Retract orbiter crew access arm (T-7:30)
Start mission recorders (T-6:15)
Start Auxiliary Power Units (T-5:00)
Arm SRB and ET range safety safe and arm devices (T-5:00)
Start liquid oxygen drainback (T-4:55)
Start orbiter aerosurface profile test (T-3:55)
Start main engine gimbal profile test (T-3:30)
Pressurize liquid oxygen tank (T-2:55)
Begin retraction of the gaseous oxygen vent arm (T-2:55)
Fuel cells to internal reactants (T-2:35)
Pressurize liquid hydrogen tank (T-1:57)
Deactivate bi-pod heaters (T-1:52)
Deactivate SRB joint heaters (T-0:60 seconds)
Orbiter transfers from ground to internal power (T-0:50 seconds)
Ground Launch Sequencer go for auto sequence start (T-0:31 seconds)
SRB gimbal profile (T-0:21 seconds)
Ignition of three space shuttle main engines (T-6.6 seconds)
SRB ignition and liftoff (T-0)

Commander (CDR): Steven Lindsey
Pilot (PLT): Mark Kelly
Mission Specialist (MS1): Michael Fossum
Mission Specialist (MS2): Lisa Nowak
Mission Specialist (MS3): Stephanie Wilson
Mission Specialist (MS4): Piers Sellers
Mission Specialist (MS5): Thomas Reiter


Saturday, July 1
5:15 a.m. - Crew wakes up
*10:10 a.m. - Crew Photo opportunity
10:48 a.m. - Weather briefing (CDR, PLT, MS2)
*11:30 a.m. - Astronauts put on flight suits
*11:58 a.m. - Depart for launch pad
*12:28 p.m. - Arrive at white room and begin to enter Discovery
*1:43 p.m. - Close crew hatch
*3:49 p.m. - Launch

For information about the STS-121 crew and its mission to the International Space Station, visit:

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