Ground-based observation of the Venus 1.27-μm O ₂ airglow

We conducted near-infrared imaging spectroscopy of the nightside of Venus with a 1.88-m telescope at Okayama Astrophysical Observatory, Japan. The 1.3-μm region spectra show 1.27-μm O ₂ airglow feature and thermal emission from the lower atmosphere. A bright airglow feature of 5 mega-Rayleigh (1 MR = 10 ¹² photons cm ^-2 s ^-1 into 4π sr) was found at around the anti-solar point, as in the previous studies. The hemispheric distribution of 1.3-μm thermal emission shows an equatorial depression similar to that of the 2.3-μm region. The hemispheric distribution of the rotational temperature shows an enhancement at around the anti-solar point overlapping the bright region. This may suggest adiabatic and/or chemical heating due to downward flow.