Adv. Space Res. Vol. 13, No. 12, pp. (12)299—(12)302, 1993 0273—1177i~3 $6.00 + 0.00 Printed in Great Britain. All rightsresa~ve& Copyright @ 1993 COSPAR EUVITA - AN EXTREME UV IMAGING TELESCOPE ARRAY WiTH SPECTRAL CAPABILITY T. J.-L. Courvoisier, 1 A. Orr,1 P. Btthler,1’2 A. Zehnder,2 R. Henneck,2 F. Stauffacher,2 J. Biakhowski,2 N. Schlumpf,2 W. Schoeps,2 A. Mchedlishvili,2 R. Sunyaev,3 V. Arefev,3 A. Yascovich,3 G. Babalyan,3 M. Pavlinsky,3 I. P. Delaboudinière,4 T. Carone,5 0. Siegmund,5 J. Warren,5 D. Leahy,6 N. Salaschenko7 and J. Platonov7 1Geneva Observatory, 1290 Sauverny, Switzerland 2 Scherrer Institute, 5232 Villigen-PSI, Switzerland 3Russian Academy of Sciences, Space Research Institute (1K!), Moscow, CIS 4lnstitut d’Astrophysique Spatiale, France 5 Science Laboratory (SSL), Berkeley, USA 6university of Calgary, Canada 7 of Applied Physics, Nizhny Novgorod, CIS Abstract EUVITA is a set of 8 extreme UV normal incidence imaging telescopes, each of them sensitive in a narrow band (A/L~\ = 15 to 80), centered at wavelengths between 50 and 175 A. Each telescope has an effective area of a few cm2, a field of view of 1.2° and a spatial resolution of 10 arcsec. EUVITA will be flown on the Russian mission SPECTRUM X-G. This satellite will be launched in a highly eccentric orbit with a period of 4 days, allowing long, unin- terrupted observations (e.g. iO~ seconds). EUVITA’s narrow spectral bands allow the measurement of source parameters such as temperature or power law index as well as interstellar absorption, and will resolve groups of strong lines emitted by optically thin hot plasmas. Introduction The EUVITA (Extreme UV Imaging Telescope Array) experiment will be flown on the Soviet Spectrum-X-G satellite along with several other experiments such as SODART (covering the range 0.2 to 20 keV, i.e. 0.6-60 A), JET-X (0.3-10 keV, or 1.2-40 A), MART-LIME (4-100 keV, 0.12-3 A) and TAUVEX (0.004-0.008 keV, 1500-3000 A). EUVITA is sensitive from 0.06 to 0.26 keV (i.e. 45-200 A), with a spatial resolution of 10 arcsec FWHM, and a spectral resolution of A/z.~.\ = 15 to 80, and is thus complementary to the other experiments aboard. The 8 EUVITA imaging telescopes will be placed along the principal axis of Spectrum-X-G, co-aligned with the JET-X and SODART experiments. This combination allows a very wide spectral coverage of the objects to be observed. This coverage is essential for understanding the emission mechanisms of the various sources and for deconvolving the emitted spectrum from interstellar effects. The EUVITA bandpasses axe at energies corresponding to the maximum emission of blackbodies with temperatures T = 3 x i0~to 106 K. All EUVITA telescopes will be operated simultaneously and so the variability of the spectral properties of sources will be monitored continuously. This is more difficult with instruments in which wavelengths are successively selected by filter wheels (as with EXOSAT or ROSAT). JASR 13:12-U (12)299