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We report preliminary results from the ALEXIS (Array of Low-Energy X-ray Imaging Sensors) ultrasoft X-ray experiment, which is scheduled to launch in spring 1993. ALEXIS is a monitor experiment that consists of 6 compact normal-incidence telescopes tuned to narrow bands centered on 66, 71, and 93 eV (186, 172, and 130 \AA). The 66 and 71 eV bandpasses are centered on a cluster of emission lines from Fe IX-XII. The 6 telescopes are arranged in pairs and cover three overlapping 33\deg fields-of-view. During each 30-second spin of the satellite, ALEXIS will monitor the entire anti-solar hemisphere. Each telescope consists of a molybdenum/silicon layered synthetic microstructure (LSM) mirror, a curved-profile microchannel plate detector situated at the prime focus, with wedge-and-strip readout, a thin lexan/titanium/boron or aluminum/carbon filter, electron- rejecting magnets, and readout electronics. The resolution of each telescope is limited by spherical aberration to about 1/2\deg diameter. ALEXIS, with its wide fields-of-view and well-defined wavelength bands, will complement NASA's Extreme Ultraviolet Explorer and the German/UK Wide Field Camera on ROSAT. It will pursue a number of scientific objectives, including mapping the diffuse background in three bands, performing a narrow-band survey of point sources, searching for transient phenomena, and monitoring variable ultrasoft X-ray sources, such as cataclysmic variables and flare stars, for weeks and months at a time. ALEXIS is serviced by a small satellite bus, launched by a Pegasus air-launched booster, and tracked by a ground station at Los Alamos. ALEXIS thereby exploits modern technology to field a space experiment better, faster, and cheaper. The ALEXIS project was developed under the auspices of the US Department of Energy.
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