Extreme ultraviolet scanning spectrometer representative of monochrometers flown on sounding rockets by the Air Force in the late 1950s through the 1970s. This instrument obtained the spectrum as an electrical signal in contrast to the earlier spectrometers that recorded spectra on photographic film. It was designed to acquire the extreme ultraviolet part of the spectrum of the sun by scanning the solar spectrum that had been dispersed from a diffraction grating. A special high-work-function photocathode scanned the spectral region from 250 to 1300 Angstroms, and the signal was amplified in the tube by a cascade amplifier, whose design was intermediate between dynodes and the later chaneltrons. This spectrometer (serial number 53) dates back to 1971 and was built by the Air Force Geophysics Laboratory under the direction of Hans Hintereggar. This is an actual flight instrument that may have flown on an Aerobee rocket. It was transferred to NASM by the U.S. Air Force in 1990.