(09/30/1998) -- Inside the Payload Changeout Room (PCR) in the Rotating Service Structure (RSS) at Launch Pad 39-B, technicians in clean suits and tethers prepare to move the payloads for mission STS-95 through the open doors of the payload bay (right) of Space Shuttle Discovery. At the top of the RSS is the Spacehab module; below it are the Spartan solar-observing deployable spacecraft, the Hubble Space Telescope Orbiting Systems Test Platform (HOST), and International Extreme Ultraviolet Hitchhiker (IEH-3). The PCR is an environmentally controlled facility with seals around the mating surface that fit against the orbiter or payload canister and permit the payload bay or canister doors to be opened and cargo removed without exposing it to outside air and contaminants. Payloads are installed vertically in the orbiter using the extendable payload ground handling mechanism. Fixed and extendable work platforms provide work access in the PCR. The SPACEHAB single module involves experiments on space flight and the aging process. Spartan is a solar physics spacecraft designed to perform remote sensing of the hot outer layers of the sun's atmosphere or corona. HOST carries four experiments to validate components planned for installation during the third Hubble Space Telescope servicing mission and to evaluate new technologies in an Earth-orbiting environment. IEH-3 comprises several experiments that will study the Jovian planetary system, hot stars, planetary and reflection nebulae, other stellar objects and their environments through remote observation of EUV/FUV emissions; study spacecraft interactions, Shuttle glow, thruster firings, and contamination; and measure the solar constant and identify variations in the value during a solar cycle. Mission STS-95 is scheduled to launch Oct. 29, 1998