Balloon-borne ultraviolet stellar echelle spectrograph

During the nights of 19, 20 May 1976 and 16, 17 September 1976, an 800-kg astronomical payload, developed by the NASA Johnson Space Center at Houston and the Astronomical Institute at Utrecht, was floating at 40-km altitude and recorded high-resolution uv spectra of stars. The spectral region of 200-340 am was covered with a spectral resolution of 0.01 nm. The optical system consisted of a 40-cm diam telescope with 1-sec of arc pointing capabilities, an echelle spectrograph working in spectral orders 66 to 112 and a SEC-vidicon integrating detector. Due to the high spectral simultaneity gain of the system 53 complete spectra of thirty-three different stars, with spectral types between 09.5 and M2 and with visual magnitudes between 0 and 4.5, could be obtained during the two nights of observation. Ozone in the residual atmosphere above 40 km reduces the atmospheric transmission around 250 nm to approximately 0.1, but with suitable integration times also in this region stars can be studied spectroscopically from balloon altitudes.