EUV Grazing-Incidence Spectrometer

When the Extreme Ultraviolet Explorer went up in 1995, it conducted a follow-up search for diffuse EUV background radiation in the interstellar medium (ISM). It was not specifically designed for diffuse observations, but it had the most sensitive equipment yet in space. It could do wide angle observation and subtract foreground sources to obtain background noise more likely due to diffuse sources. It found a clean spectrum with broad emission lines at 304 Å, 537 Å, and 584 Å, but none of the unexplained lines picked up by the earlier spectrometers on Bowyer's sounding rocket.