Extreme ultraviolet spectra of Venusian airglow observed by EXCEED

Abstract

Extreme ultraviolet (EUV) spectra of Venus in the wavelength range 520−1480 Å with 3−4 Å resolutions were obtained in March 2014 by an EUV imaging spectrometer EXCEED (Extreme Ultraviolet Spectroscope for Exospheric Dynamics) on the HISAKI spacecraft. Due to its high sensitivity and long exposure time, many new emission lines and bands were identified. Already known emissions such as the O II 834 Å, O I 989 Å, HILy−β1026 Å, and the C I 1277 Å lines (Broadfoot et al., 1974; Bertaux et al., 1980; Feldman et al., 2000) are also detected in the EXCEED spectrum. In addition, N2 band systems such as the Lyman-Birge-Hopfield (a1Πg−X1Σg+) (2, 0), (2, 1), (3, 1), (3, 2) and (5, 3) bands, the Birge-Hopfield (b1Πu−X1Σg+) (1, 3) band, and the Carroll-Yoshino (c4′1Σu+−X1Σg+) (0, 0) and (0, 1) bands together are identified for the first time in the Venusian airglow. We also identified the CO Hopfield-Birge (B1Σ+−X1Σ+) (1, 0) band in addition to the already known (0, 0) band, and the CO Hopfield-Birge (C1Σ+−X1Σ+) (0, 1), (0, 2) bands in addition to the already known (0, 0) band (Feldman et al., 2000; Gérard et al., 2011).