EURD OBSERVATIONS OF EUV NIGHTIME AIRGLOW LINES

The extreme ultraviolet (EUV) airglow has yet to be studied extensivel y due to observational difficulties in this range of the spectrum. EUR D is an instrument designed to study diffuse EUV radiation flown on th e Spanish MINISAT-01 satellite. In this paper we present observations of the terrestrial night airglow as observed from EURD in the range of 400 to 1060 Angstrom. The high sensitivity and high resolution of the instrument, compared with previous observations, and the long integra tion times provided by MINISAT-01 permits the identification for the f irst time of the complete Lyman series of atomic hydrogen resolving up to Lyman epsilon. It has also been possible to identify a feature at 537 Angstrom as helium Lyman beta line and the detection of other line s of the blended Lyman series of helium at 515 and 522 Angstrom.