EIT: Extreme-ultraviolet imaging telescope for the SOHO mission

The Extreme-ultraviolet Imaging Telescope (EIT) will provide wide-field images of the corona and transition region on the solar disc and up to 1.5 R. above the solar limb. Its normal incidence multilayer-coated optics will select spectral emission lines from Fe IX (171 Angstrom), Fe XII (195 Angstrom), Fe XV (284 Angstrom), and He II (304 Angstrom) to provide sensitive temperature diagnostics in the range from 6 x 10(4) K to 3 x 10(6) K. The telescope has a 45 x 45 arcmin field of view and 2.6 arcsec pixels which will provide approximately 5-arcsec spatial resolution. The EIT will probe the coronal plasma on a global scale, as well as the underlying cooler and turbulent atmosphere, providing the basis for comparative analyses with observations from both the ground and other SOHO instruments. This paper presents details of the EIT instrumentation, its performance and operating modes.