Tomographic extreme-ultraviolet spectrographs: TESS

We describe the system of Tomographic Extreme Ultraviolet (EUV) Spectrograp hS (TESS) that are the primary instruments for the Tomographic Experiment u sing Radiative Recombinative Ionospheric EUV and Radio Sources (TERRIERS) s atellite. The spectrographs were designed to make high-sensitivity {80 coun ts/s)/Rayleigh [one Rayleigh is equivalent to 10(6) photoas/(4 pi str cm(2) s)}, line-of-sight measurements of the or 135.6- and 91.1-nm emissions suit able for tomographic inversion. The system consists of five spectrographs, four identical nightglow instruments (for redundancy and added sensitivity) , and one instrument with a smaller aperture to reduce sensitivity and incr ease spectral resolution for daytime operation. Each instrument has a bandp ass of 80-140 nm with approximately 2- and 1-nn resolution for the night an d day instruments, respectively. They utilize microchannel-plate-based two- dimensional imaging detectors with wedge-and-strip anode readouts. The inst ruments were designed, fabricated, and calibrated at Boston University, and the TERRIERS satellite was launched on 18 May 1999 from Vandenberg Air For ce Base, California. (C) 2000 Optical Society of America OCIS codes: 000.21 70, 040.0040, 110.6960, 120.4640, 120.6200, 300.6540.