16-hour per day, Monday through Friday staffing profile in the Extended Mission. Less redundancy and less access to ongoing engineering support were consistent with NASA policy for missions in their extended phase, where a higher level of risk is allowed. Spacecraft The FUSE satellite consists of two primary sections, the spacecraft and the science instrument. The spacecraft contains all of the elements necessary for powering and pointing the satellite, including the Attitude Control System, the solar panels, and communications-electronics and antennas. The observatory is approximately long with a baffle fully deployed. Instrument The FUSE science instrument consists of four co-aligned telescope mirrors (~ clear aperture) based on a Rowland circle design. The light from the four optical channels is dispersed by four spherical, aberration-corrected holographic diffraction gratings, and recorded by two delay-line microchannel plate detectors. Two channels with Silicon carbide (SiC) coatings cover the range 90.5–110 nm and two channels with Lithium fluoride (LiF) coatings cover the range 100–119.5 nm. Actuators on the mirror mountings kept the focus to 90% encircled energy within 1.5". A Fine Error Sensor (FES) with a 21' square field maintained the spacecraft pointing stability to 0.5 arcseconds. Each mirror has a corresponding astigmatism-corrected, holographically-ruled diffraction grating, each one on a curved substrate so as to produce four Rowland circle spectrographs. The dispersed ultraviolet light is detected by two microchannel plate detector intensified double delay-line detectors, whose surfaces are curved to match the curvature of the focal plane. Operations The FUSE observatory was designed for an operational lifetime of three years, although it was hoped that it might remain operational for as long as ten years. NASA since recommended an additional two-year extension beyond the prime mission. FUSE was controlled through a primary ground station antenna located at the University of Puerto Rico at Mayagüez. FUSE brought it over the ground station for less than 10 minutes at a time (on average) for about six or seven orbits in a row, followed by roughly seven or eight orbits without contact. Hence, the satellite had to operate on its own most of the time, moving from target to target, identifying star fields, centering objects in the spectrograph apertures, and performing the observations. The scientific data, which was stored in digital form, was radioed to the ground during contact with the ground station. FUSE Science Operations were on hold from 10 December 2001, to approximately the end of