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In the Vehicle Assembly Building, Michael Cinquigianno (left), who is a system test mechanical technician with Lockheed Martin, checks out the vent valve assembly on External Tank 121. Next to him is Lance Mercier, with Lockheed Martin Quality Control. The assembly sits on top of the tank and, when on the launch pad, is connected to the beanie cap, a swing-arm-mounted cap that covers the oxygen tank vent on top of the tank during the countdown. The cap is retracted about two minutes before liftoff. The cap siphons off oxygen vapor that threatens to form large ice on the tank, thus protecting the orbiters thermal protection system during launch. The External Tanks are built by Lockheed Martin at the Michoud Assembly Facility near New Orleans. The tank is being prepared to fly with Discovery on mission STS-114, whose launch window extends July 13 to July 31.