NASA will begin the launch countdown for Space Shuttle Atlantis’ STS-115 mission at 6 p.m. EDT Thursday, Aug. 24, at the T-43 hour point. During this mission, Atlantis’ crew will resume construction of the International Space Station, which is the goal of the remaining space shuttle flights until the spacecraft are retired in 2010.

The NASA Kennedy Space Center launch team will conduct the countdown from the newly renovated firing room 4 of the Launch Control Center. The countdown includes 27 hours, 24 minutes of built-in hold time leading to a preferred launch time at about 4:30 p.m. on Sunday, Aug. 27. The launch window for that day extends an additional five minutes.

This mission is the 116th space shuttle flight, the 27th flight for Atlantis and the 19th U.S. flight to the International Space Station. STS-115 is scheduled to last 11 days with a landing at Kennedy about 12:02 p.m. EDT on Sept. 7.

Atlantis’ last mission was STS-112 in October 2002. In preparation for STS-115, Atlantis was moved into Kennedy’s Vehicle Assembly Building on July 24. Atlantis then was attached to its modified external tank and solid rocket boosters. Space Shuttle Atlantis was rolled out to Launch Pad 39B on Aug. 2.

The STS-115 crew is Commander Brent Jett, Pilot Chris Ferguson, and mission specialists Joe Tanner, Dan Burbank, Heide Stefanyshyn-Piper and Canadian astronaut Steve MacLean.

During STS-115, Atlantis’ astronauts will deliver and install the 17.5-ton, bus-sized P3/P4 integrated truss segment on the station. The girder-like truss includes a set of giant solar arrays, batteries and associated electronics. The P3/P4 truss segment will provide one-fourth of the total power-generation capability for the completed station.

For information about the STS-115 crew and its mission to the International Space Station, visit:

http://www.nasa.gov/shuttle

STS-115 LAUNCH COUNTDOWN MILESTONES AND TIMES

(All times Eastern)

Launch-3 Days (Thursday, Aug. 24)

  • Prepare for the start of the STS-115 launch countdown
  • Perform the call to stations (5:30 p.m.)
  • Countdown begins at the T-43 hour mark (6 p.m.)
  • Begin final vehicle and facility closeouts for launch
  • Check out backup flight systems
  • Review flight software stored in mass memory units and display systems
  • Load backup flight system software into Atlantis’ general purpose computers

Launch-2 Days (Friday, Aug. 25)

  • Remove flight-deck platforms (2:30 a.m.)
  • Complete preparation to load power reactant storage and distribution system (5 a.m.)
  • Activate and test navigational systems (7 a.m.)
  • Flight deck preliminary inspections complete (10 a.m.)

  • Enter first built-in hold at T-27 hours for duration of 4 hours (10 a.m.)

  • Clear launch pad of all non-essential personnel
  • Perform test of the vehicle’s pyrotechnic initiator controllers
  • Resume countdown (2 p.m.)

  • Begin operations to load cryogenic reactants into Atlantis’ fuel cell storage tanks (2 p.m.)

  • Enter 4-hour built-in hold at T-19 hours (10 p.m.)

  • Demate orbiter mid-body umbilical unit (10:30 p.m.)
  • Resume orbiter and ground support equipment closeouts

Launch-1 Day (Saturday, Aug. 26)

Resume countdown (2 a.m.)

  • Final preparations of the shuttle’s three main engines for main
  • propellant tanking (2 a.m.)
  • Begin filling pad sound suppression system water tank (4 a.m.)
  • Pad sound suppression system water tank filling complete (7 a.m.)
  • Close out the tail service masts on the mobile launcher platform
  • Begin star tracker functional checks (9:50 a.m.)

  • Enter planned hold at T-11 hours for 13 hours, 34 minutes (10 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 (3:10 p.m.)
  • Move Rotating Service Structure to the park position (7 p.m.)
  • Perform ascent switch list
  • Fuel cell flow-through purge complete

  • Resume countdown at T-11 hours (11:34 p.m.)

Launch Day (Sunday, Aug. 27)

  • Activate the orbiter’s fuel cells (12:45 a.m.)
  • Clear the blast danger area of all non-essential personnel
  • Switch Atlantis’ purge air to gaseous nitrogen (1:20 a.m.)

  • Enter planned 2-hour built-in hold at the T-6 hour mark (4:34 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 (6:34 a.m.)
  • Chilldown of propellant transfer lines (6:34 a.m.)
  • Begin loading the external tank with about 500,000 gallons of
  • cryogenic propellants (about 6:44 a.m.)
  • Complete filling the external tank with its flight load of liquid hydrogen and liquid oxygen propellants (about 9:34 a.m.)
  • Final Inspection Team proceeds to launch pad

  • Enter planned 3-hour built-in hold at T-3 hours (9:34 a.m.)

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

  • Resume countdown at T-3 hours (12:34 p.m.)

  • Crew departs Operations and Checkout Building for the pad (12:40 p.m.)
  • Complete closeout preparations in the White Room
  • Check cockpit switch configurations
  • Flight crew begins entry into the orbiter (about 1:10 p.m.)
  • Astronauts perform air-to-ground voice checks with Launch and Mission Control
  • Begin to close Atlantis’ crew hatch (about 2 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 (3:14 p.m.)

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

  • Resume countdown at T-20 minutes (3:24 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 (3:35 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 4:21 p.m.)

  • Start automatic ground launch sequencer (T-9 minutes)
  • Retract orbiter crew access arm (T-7:30)
  • Start mission recorders (T-6:15)
  • Start Auxiliary Power Units (T-5)
  • Arm solid rocket booster and external tank range safety safe and arm devices (T-5)
  • 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 solid rocket booster joint heaters (T-1)
  • Orbiter transfers from ground to internal power (T-0:50 seconds)
  • Ground Launch Sequencer go for auto sequence start (T-0:31 seconds)
  • Booster gimbal profile (T-0:21 seconds)
  • Ignition of three space shuttle main engines (T-6.6 seconds)
  • Booster ignition and liftoff (T-0)

CREW FOR MISSION STS-115

Commander: Brent Jett
Pilot: Chris Ferguson
Payload Commander (MS1): Joe Tanner
Mission Specialist (MS2): Dan Burbank
Mission Specialist (MS3): Heide Stefanyshyn-Piper
Mission Specialist (MS4): Steve MacLean

SUMMARY OF STS-115 LAUNCH DAY CREW ACTIVITIES

Sunday, Aug. 27

6:30 a.m. Crew wakes up

7 a.m. Breakfast

–10:55 a.m. Television coverage from crew quarters

Noon Weather briefing

–12:10 p.m. Don flight suits
–12:40 p.m. Depart for launch pad
–1:10 p.m. Arrive at White Room and begin ingress
–2:25 p.m. Close crew hatch
–4:30 p.m. Launch

— Televised events (times may vary slightly)

All times Eastern