A schematic diagram of the proposed EUV transmission grating spectrometer using three isolated silicon photodiodes as detectors is shown in the left pane. The photodiodes used are of the type flown successfully by us aboard a sounding rocket at the White Sands Missile Range in which obtained the integrated absolute solar EUV flux in the Al band pass (Ogawa et al. 1990).

To achieve spectral resolution as well, a free standing X-ray transmission grating (5000 grooves/mm) is placed on the optic axis between two highly stable (1500 Å thick each) alumin um filters. The filters not only limit the radiation that enters the spectrometer to the Al transmission band pass (170 - 700 Å), but when placed in series with each other as shown will also serve to sensibly eliminate the effects due to any pinholes which may develop.