Extreme UV spectroheliometer on the Apollo Telescope Mount

The extreme UV spectroheliometer flown on ATM observed within the 280-1340 A spectral range at seven wavelengths simultaneously, with a spatial resolution element 5 x 5 sq arcsec field of view in 5.5 min. The instrument could also obtain spectral scans over the same wavelength range with a spectral resolution of 1.6 A in 3.8 min. The instrument is described in detail with attention given to the telescope, the spectrometer, and the detection system.