UVSTAR: an imaging spectrograph with telescope for the shuttle Hitchhiker-M platform

UVSTAR (Ultraviolet Spectrograph Telescope for Astronomical Research) is an EUV spectral imager intended as a facility instrument devoted to solar system and stellar astronomy. It covers the wavelength range of 500 to 1250 A, with sufficient spectral resolution to separate atomic emission lines and to form spectrally resolved images of extended plasma sources. Targets include the lo plasma torus at Jupiter, hot stars, and planetary nebulae. UVSTAR will make useful measurements of emissions from Earth's atmosphere as well. UVSTAR consists of a pair of telescopes and concave-grating spectrographs that cover the overlapping spectral ranges of 500 to 900 and 850 to 1250 A. The telescopes use two 30-cm-diam off-axis paraboloids having a focal length of 1.4 m. An image of the target is formed at the entrance slits of two concave grating spectrographs. The gratings provide dispersion and reimage the slits at the detectors, intensified CCDs. The readout format of the detectors can be chosen by computer, and three slit widths are selectable to adapt the instrument to specific tasks. The spectrograph package has internal gimbals, which allow rotation of ±3 deg about each of two axes. Dedicated finding and tracking telescopes will acquire and track the target after rough pointing is achieved by orienting the Orbiter. Responsibilities for the implementation and utilization of UVSTAR are shared by groups in Italy and the United States. UVSTAR is scheduled for flight in early 1995, timed for an opportunity to observe the Jovian system.