T-43 hours (T minus 43 hours) and counting

The Shuttle Test Director performs the traditional call to stations and the countdown clock is activated.

• 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 the orbiter's general purpose computers
  
• Remove middeck and flight deck platforms
  
• Activate and test navigational systems
  
• Complete preparation to load power reactant storage and distribution system
  
• Complete flight deck preliminary inspections