The countdown includes 30 hours and 33 minutes of built-in hold time leading to the opening of the launch window at about 3:33 a.m. (EST) on March 21. The launch window extends for 6 - 10 minutes. The exact time of launch will be determined about 90 minutes before liftoff based on the location of the Mir space station. (The expected time of launch is closer to 3:35 a.m., but controllers are preparing for launch as early as 3:33 a.m.)
In order to accommodate the short window necessary to rendezvous and dock with Mir, some changes have been made to the standard launch countdown. Most significant is the addition of an extra 30 minutes to the normal 10 minute built-in hold at T-9 minutes. Also, tanking is scheduled to begin about 30 minutes earlier than normal.
STS-76 is the third Space Shuttle mission of 1996. This will be the 16th flight of the orbiter Atlantis and the 76th flight overall in NASA s Space Shuttle program.
Atlantis was rolled out of Orbiter Processing Facility bay 1 on Feb. 19 and mated with the external tank and solid rocket boosters in the Vehicle Assembly Building. The Shuttle stack was then transported to Pad 39B on Feb. 28. Atlantis last flew on the second Shuttle/Mir docking flight in November 1995.
Atlantis will carry into orbit a six member crew. Mission Specialist Shannon Lucid will remain on the Mir space station with the cosmonaut crew now on board. She will remain there until Atlantis again docks with Mir in August.
The STS-76 crew are: Commander Kevin Chilton; Pilot Richard Searfoss; and Mission Specialists Shannon Lucid, Linda Godwin, Rich Clifford and Ronald Sega. All members of the STS-76 crew are veteran Shuttle flyers.
The STS-76 crew are scheduled to arrive at KSC at about 12 a.m. Monday, March 18. Their activities at KSC prior to launch will include equipment fit checks, medical examinations and opportunities to fly in the Shuttle Training Aircraft.
Enter first planned built-in hold at T-27 hours for duration of four hours (6 p.m.)
- Clear launch pad of all non-essential personnel
- Perform test of the vehicle's pyrotechnic initiator controllers
Resume countdown (10 p.m.)
- Clear launch pad of all personnel
Enter eight-hour built-in hold at T-19 hours (6 a.m.)
- Resume orbiter and ground support equipment close-outs
- Demate orbiter mid-body umbilical unit and retract into fixed service
structure
Resume countdown (2 p.m.)
- Start final preparations of the Shuttle's three main engines for main
propellant tanking and flight
- Activate the orbiter"s flight controls and navigation systems
- Install mission specialists' seats in crew cabin
- Close-out the tail service masts on the mobile launcher platform
Enter planned hold at T-11 hours for 13 hours, 43 minutes (10 p.m.)
Resume countdown (11:43 a.m.)
- Continue installation of time critical flight crew equipment
- Perform pre-ingress switch list
- Start fuel cell flow-through purge
- Activate the orbiter's fuel cells
- Configure communications at Mission Control, Houston, for launch
- Clear the blast danger area of all non-essential personnel
- Switch Atlantis' purge air to gaseous nitrogen
Enter planned two-hour built-in hold at the T-6 hour mark (4:43 p.m.)
- Launch team verifies no violations of launch commit criteria prior to
cryogenic loading of the external tank
- Clear pad of all personnel
- Begin loading the external tank with about 500,000 gallons of cryogenic
propellants (about 6:13 p.m.)
Resume countdown (6:43 p.m.)
- Complete filling the external tank with its flight load of liquid hydrogen
and liquid oxygen propellants (about 9:13 p.m.)
- Perform inertial measurement unit preflight calibration
- Align Merritt Island Launch Area (MILA) tracking antennas
- Perform open loop test with Eastern Range
- Conduct gimbal profile checks of orbital maneuvering system engines
Enter two-hour hold at T-3 hours (9:43 p.m.)
- Close-out crew and Final Inspection Team proceeds to Launch Pad 39B
Resume countdown at T-3 hours (11:43 p.m.)
- Crew departs Operations and Checkout Building for the pad (about 11:50
p.m.)
- Complete close-out preparations in the white room
- Check cockpit switch configurations
Launch Day (Thursday, March 21)
- Flight crew begins entry into the orbiter (about 12:20 a.m.)
- Astronauts perform air-to-ground voice checks with Launch Control and
Mission Control
- Close Atlantis' crew hatch (about 1:35 a.m.)
- Begin Eastern Range final network open loop command checks
- Perform hatch seal and cabin leak checks
- Complete white room close-out
- Close-out 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 (2:23 a.m.)
- NASA Test Director conducts final launch team briefings
Resume countdown (2:33 a.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 40-minute hold at T-9 minutes (2:44 a.m.)
(This is the last planned built-in hold. Other hold options are available if
necessary. During this hold, the exact launch time will be determined based
on the exact location of the Mir space station. The hold time will likely
vary.)
- Launch Director, Mission Management Team and NASA Test Director conduct final polls for go/no go to launch
Resume countdown at T-9 minutes (3:24 a.m.)
- Start automatic ground launch sequencer (T-9:00 minutes)
- Retract orbiter crew access arm (T-7:30)
- Start mission recorders (T-5:30)
- 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 SRB joint heaters (T-1:00)
- 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)
T-TIME LENGTH OF HOLD HOLD BEGINS HOLD ENDS T-27 hours 4 hours 6:00 p.m. Mon. 10:00 p.m. Mon. T-19 hours 8 hours 6:00 a.m. Tues. 2:00 p.m. Tues. T-11 hours 13 hours, 43 minutes 10:00 p.m. Tues. 11:43 a.m. Wed. T-6 hours 2 hours 4:43 p.m. Wed. 6:43 p.m. Wed. T-3 hours 2 hours 9:43 p.m. Wed. 11:43 p.m. Wed. T-20 minutes 10 minutes 2:23 a.m. Thurs. 2:33 a.m. Thurs. T-9 minutes 40 minutes 2:44 a.m. Thurs. 3:24 a.m. Thurs.
Commander (CDR): Kevin Chilton Pilot (PLT): Richard Searfoss Mission Specialist (MS1): Ronald Sega Mission Specialist (MS2): Rich Clifford Mission Specialist (MS3): Linda Godwin Mission Specialist (MS4): Shannon Lucid
Wednesday, March 20 4:30 p.m. Wake up 5:00 p.m. Breakfast * 10:40 p.m. Lunch and crew photo 11:10 p.m. Weather briefing (CDR, PLT, MS2) 11:10 p.m. Don launch and entry suits (MS1, MS3, MS4) 11:20 p.m. Don launch and entry suits (CDR, PLT, MS2) * 11:35 p.m. Crew suiting photo * 11:50 p.m. Depart for launch pad 39B Thursday, March 21 * 12:20 a.m. Arrive at white room and begin ingress * 1:35 a.m. Close crew hatch * 3:35 a.m. Launch* Televised events (times may vary slightly)