In the Payload Hazardous Servicing Facility workers move the Hubble Fine Guidance Sensor or FGS.

In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, workers move the Hubble Fine Guidance Sensor, or FGS, before removing the protective cover. The FGS will be integrated onto the Orbital Replacement Unit carrier in the clean room of the facility. The sensor will extend the life of the pointing control system on the Hubble Space Telescope. On the mission, this FGS will replace one of the three sensors that is failing and thus outfit the telescope with two completely healthy units, which are needed. A third, older FGS aboard the telescope will provide additional target-pointing efficiency and redundancy. Space shuttle Atlantis is targeted to launch on the STS-125 mission Oct. 8. Photo credit: NASA/Jack Pfaller