STS-91 (91)

Discovery (24)
Pad 39-A (66)
91st Shuttle Mission
24th Flight OV-103
1st flight SLWT

NOTE: Click Here for Countdown Homepage


Charles J. Precourt (4), Commander
Dominic L. Pudwill Gorie (1), Pilot
Wendy B. Lawrence (3), Mission Specialist
Franklin R. Chang-Diaz (6), Mission Specialist
Janet L. Kavandi (1), Mission Specialist
Valery Victorovitch Ryumin (4), Mission Specialist

Andrew S. W. Thomas (Mir-25/STS-89) will return


OPF -- 08/19/97 (Reference KSC Shuttle Status 08/19/1997)
VAB -- 10/01/97 (Storage)
OPF2 -- 10/30/97 (Reference KSC Shuttle Status 10/30/1997)
VAB -- 04/27/98 (Reference KSC Shuttle Status 4/28/1998)
PAD -- 05/02/98 (Reference KSC Shuttle Status 5/04/1998)
FRR -- 05/19/98 (Reference KSC Shuttle Status 5/18/1998)


Mir-Docking/9, AMS, SPACEHAB-SM, GAS(G-722, G-743)

(Reference KSC Shuttle Status May 1998)
(Reference KSC Shuttle Status Jun 1998)

Mission Objectives:

Click here for Additional Info on STS-91

STS-91 will mark the final Shuttle/Mir Docking Mission. This Phase 1 Program is a precursor to the International Space Station maintaining a continuous American presence in space and developing the procedures and hardware required for an international partnership in space.

STS-91 will also carry into space the Alpha Magnetic Spectrometer Investigation (AMS). The objectives of this investigation are to search for anti-matter and dark matter in space and to study astrophysics.

The mission will also be the first use of the super lightweight external tank (SLWT) which is the same size (154ft long and 27ft in diameter) as the external tank used on previous launches but 7,500 lbs lighter. The tank is made of an aluminum lithium alloy and the tank's structural design also has been improved making it 30% stronger and 5% less dense. The walls of the redesigned hydrogen tank are machined in an orthogonal waffle-like pattern, providing more strength and stability than the previous design. These improvements will provide additional payload capacity to the International Space Station. (Reference NASA Press Release 98-6)


Launch June 2, 1998 6:06:24 p.m. EDT at the opening of the 10 minute launch window.

On Tuesday, June 2, 1998 launch preparations continued on schedule. Go for tanking was given at 9:30am after receiving a briefing about the readiness of the Mir Space station. By noon, at the T-minus 3 hour mark, LH2 cryogenic propellant loading was complete and in stable replenish mode. Loading of the Liquid Oxygen tank was about 80% complete. At 12:30am EDT, tanking operations were complete and the external tank was in stable replenish mode. The crew departed the Operations and Checkout Building at 2:19pm EDT, traveled to Launch Pad 39A and were installed into the orbiter by 3:30pm EDT. At 4:02pm EDT the Discovery's hatch was closed for flight. At 5:47pm EDT and T-minus 25 minutes and counting the white room close out was complete and the closeout team left Launch Pad 39A. At T-minus 14 minutes and holding, the mission management team decided to move the T-0 time to the opening of the launch window at 6;06pm EDT. At 5:15pm EDT, the countdown entered a planned 40 minute hold at the T-minus 9 minute and holding mark. At 17:57 EDT the coundown came out of the T-minus 9 minute hold with the only concern being tracked was a slightly low pressure on the Orbiter Access Arm (OAA). The OAA retracted successfully at 17:59 EDT. Liftoff occured at 6:06pm EDT. SRB Sep 2.5min into flight, downrange 56 miles.

On Monday, June 1, 1998, launch preparations continued on schedule and final preflight preparations of Shuttle main engines concluded. On Tuesday, at about 12:30 a.m. the Rotating Service Structure will be retracted into the launch position. Loading of the external tank with its flight load of cryogenic propellants begins at about 9:14 a.m. 6/2/98 and continues for about 3 hours. Managers continue to monitor the situation with Mir's motion control computer. At this time, systems aboard Mir have stabilized sufficiently for managers to proceed with countdown operations. A final check of Mir's systems will occur prior to tanking activities tomorrow morning. (Reference KSC Shuttle Status 6/1/1998)

On Sunday, May 31, 1998, The countdown for launch of mission STS-91 began as scheduled at 9 p.m. 5/30/98 at the T-43 hour mark. All pre-launch activities at Kennedy Space Center.continue without problem toward a target lift-off time of 6:10 p.m. on Tuesday, June 2, from Launch Pad 39A. Today at KSC, engineers are preparing the Shuttle Discovery for the loading of cryogenic reactants into the onboard power reactant and storage distribution tanks. Loading is set to begin at about 5 p.m. Prior to this operation, a standard orbiter and solid rocket booster pyrotechnic initiator controller test will be performed. Cryogenic loading operations are expected to conclude by midnight tonight. (Reference KSC Shuttle Status 5/31/1998)

On Saturday, May 30, 1998 The countdown for launch of mission STS-91 remains on schedule to begin tonight at 9 p.m. at the T-43 hour mark. All prelaunch activities continue on schedule. The contingency space suits have been installed into the orbiter's airlock and check-out of those suits completed. Flight crew equipment stowage in the orbiter's mid-deck continued and aft main engine compartment close-outs were completed and final main propulsion system checks under way. The crew for mission STS-91 arrived at KSC's Shuttle Landing Facility at about 12:50 p.m. EDT. They will spend the days prior to launch at KSC reviewing their flight plans, undergoing final medical examinations and flying in the Shuttle Training Aircraft. (Reference KSC Shuttle Status 5/30/1998)

On Thursday, May 28, 1998, preparations to begin the launch countdown for mission STS-91 at 9:00pm on Saturday are proceeding on schedule. Installation and checkout of the ordnance on the solid rocket boosters are complete. Refilling of Discovery's orbiter maneuvering system oxidizer tank concluded yesterday and pressurization of the hypergolic system began this morning. Aft main engine compartment close-outs have resumed today and will conclude Saturday with aft door installation. The STS-91 flight crew arrives at KSC Saturday at 12:30 p.m. (Reference KSC Shuttle Status 5/28/1998)

On Thursday, May 14, 1998, close-outs of Discovery's aft compartment continued in preparation for Monday's tanking test of the first super lightweight external tank. Shuttle integrated voltage tests began. On Wednesday, technicians opened the orbiter's payload bay doors and completed SPACEHAB tunnel leak checks. SPACEHAB interface verification testing (IVT) is under way and the AMS IVT is set for Friday. (Reference KSC Shuttle Status 5/14/1998)

On Monday, May 11, 1998, replacement of Discovery's master event controller No. 1 and the change-out of multiplexer demultiplexer No. 4 are complete. Over the weekend, technicians completed work on the mobile launch platform's gaseous nitrogen system. The payload bay doors are closed and crew module/SPACEHAB pressure leak checks are complete. (Reference KSC Shuttle Status 5/11/1998)

On Saturday, May 2, 1998 Space Shuttle Discovery rolled out of the Vehicle Assembly Building at 3:26 a.m. and arrived at Pad 39A at about 9:30 a.m. Once at the pad, hotfire testing of Discovery's three auxiliary power units was completed and launch pad validations began. On Sunday, the payload was installed into the payload changeout room. The Rotating Service Structure has been extended to the vehicle and the orbiter's payload bay doors are slated to be opened later today. Pad validations continued. The STS-91 flight crew arrived
at KSC monday evening for the Terminal Countdown Demonstration Test set for Wednesday and Thursday. (Reference KSC Shuttle Status 05/04/1998)

On Monday, April 27, 1998, Discovery was transferred from Orbiter Processing Facility bay 2 to the Vehicle Assembly Building. The orbiter arrived in the VAB just after 5 p.m. Efforts to mate Discovery to the new super lightweight external tank in high bay 1 will conclude 4/28/98. The entire Shuttle stack is scheduled for transport to Pad 39A later this week. NASA managers decided on Tuesday to move the STS-91 target launch date to June 2. The additional time will accommodate orbiter processing requirements and launch preparations at Pad 39A. (Reference KSC Shuttle Status 4/28/1998)

The new super lightweight external tank, to be used on STS-91, arrived at KSC s turn basin at about 11 a.m. on Friday 2/6/98. Workers transported the 154-foot-long improved tank to the Vehicle Assembly Building (VAB) this afternoon, where it will undergo processing for flight. The new tank weighs about 7,500 pounds less than the original ET. (Reference KSC Shuttle Status 2/06/1998)


Inclination: 51.60
Duration: 9 days, 19 hours, 53 minutes, seconds. (Estimated)
Distance: miles


ET : SN-96
SSME-1: SN-2047**A (HPOTP 8025, HPFTP 2232)
SSME-2: SN-2040* (HPOTP 8017, HPFTP 6113)
SSME-3: SN-2042* (HPOTP 8019, HPFTP 6011)


KSC June 12, 1998 2:00:17 p.m. EDT. Unofficial main gear touchdown at MET 9 days, 19 hours, 53 minutes, 57 seconds (2:00 pm EDT). Nose gear touchdown was 5 seconds later at MET 9 days, 19 hours, 54 minutes, and 2 seconds. Wheel stop occurred at MET 9 days, 19 hours, 55 minutes, and 1 second (2:01 pm EDT).

Deorbit burn occurred approximately at 12:51 p.m. EDT. A go for deorbit burn was given at 12:31 p.m.

Mission Highlights:

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Last Updated Friday June 29 11:37:03 EDT 2001
Jim Dumoulin (