[PPS05-P02] Temperature and wind variations in Venusian mesosphere and lower thermosphere by mid-infrared heterodyne spectrometer in 2018
Keywords:Venus, Mesosphere, mid-infrared spectroscopy
Our Mid-Infrared Laser Heterodyne Instrument (MILAHI) have been inserted to Tohoku 60 cm telescope located the summit of Mt. Haleakala in Maui, Hawaii (Nakagawa et al., 2016). MILAHI has 10 um CO2 laser as local oscillator. The field of view is 4 arcsec with 60 cm telescope and in the wavelength of 10 um. MIR-HS can retrieve temperature and wind in different altitude between dayside observations and nightside observations. CO2 emerge non-local thermodynamic equilibrium emission from 100 – 120 km altitude in dayside (Lopez-Valverde et al., 2011). Temperature and wind are derived from Doppler width and Doppler shift of the emission spectra, respectively. In nightside, CO2 in the mesosphere absorbs background radiation from the cloud deck. Temperature profile and wind are retrieved from this absorption spectra with radiative transfer equation and inverse method of AMATERASU developed in National Institute of Information and Communications Technology.
Dayside observations were conducted between 24th and 27th in June, 2018. Apparent diameter was 15 arcsec and apparent dayside was half of the disk in this term. Observed points were North, South, disk center, and equator with integration times of 30 - 55 minutes. Each observed point gave different temperature variation feature. Temperature variation range was 170 - 220 K in agreement with Sonnabend et al. (2010). Temperature distribution showed both latitudinal dependence in 25th and convergence at 200 K in 26th.
Nightside observations were conducted from 11th to 13th, 19th, and 20th in November, 2018. Apparent diameter of Venus changed between 55.4 and 49.4 arcsec after inferior conjunction. We observed equator with three days, north 33 degree and south 33 degree for diurnal and latitudinal variations with integration times of 80 - 130 minutes. The observed spectra in the unit of relative intensity are under conversion because the retrieval with AMATERASU is necessary to use absolute radiation. We will show retrieved temperature profile and wind velocity at this presentation.