The EXOSAT transmission grating spectrometer (TGS) consisted of two gratings, a 1000 lmm-1 grating behind one of the two LE (low energy) telescopes, and a 500 lmm-1 behind the other telescope. Also this instrument was developed by SRON. Channel multiplier arrays (CMA), detectors similar to the Einstein HRI, were used to read out the spectra. Additionally, different photometric filters could be placed in front of the detectors. The spectrometers had a maximum effective area of about 10 cm2 at 100 A . With the TGS, 23 objects were observed in an estimated total observing time of 600ks starting in 1983 (Fig. 8.5). Because of a malfunction of the grating insertion mechanism, most of these 23 objects could be observed only with insufficient observing time, apart from the very bright X-ray/EUV sources HZ43 and Sirius B, which have been extensively studied.
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