This was the twenty-fourth Discovery flight. STS 91 marked 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. Carried the Alpha Magnetic Spectrometer Investigation (AMS) to search for anti-matter and dark matter in space and to study astrophysics. First use of the super lightweight external tank (SLWT), same size as previous but 7,500 lbs. lighter. This will provide additional payload capacity to the International Space Station. Brought Thomas (arrived MIR on STS 89)back from MIR. Landed at Kennedy Space Center, FL. June 12, 1998. Mission Duration: 9 days 19 hours 55 minutes and 1 second. Launch Date: June 2, 1998 6:06 PM EDT Launch Vehicle: Discovery. Crew: Commander – Charles J. Precourt, Pilot – Dominic L. Pudwill Gorie, Mission Specialists – Wendy B. Lawrence, Franklin R. Chan-Diaz, Janet L. Kavandi, Valery Voctorovitch Ryumin, Download: Andrew S. W. Thomas. Iron-on. 3.75″ diameter.