Terahertz and far-infrared windows opened at Dome A in Antarctica

• Published in: Nature astronomy Vol. 1; no. 1
• Main Authors: Shi, Sheng-Cai, Paine, Scott, Yao, Qi-Jun, Lin, Zhen-Hui, Li, Xin-Xing, Duan, Wen-Ying, Matsuo, Hiroshi, Zhang, Qizhou, Yang, Ji, Ashley, M. C. B., Shang, Zhaohui, Hu, Zhong-Wen
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.01.2017; Nature Publishing Group
• Subjects: 639/33/34/2810; Absorption; Astronomy; Astrophysics and Cosmology; Atmosphere; Fourier transforms; letter; Physics; Radiative transfer; Thermal radiation; Water vapor; Antarctica
• ISSN: 2397-3366; 2397-3366
• DOI: 10.1038/s41550-016-0001

The terahertz and far-infrared band, ranging from approximately 0.3 THz to 15 THz (1 mm to 20 μm), is important for astrophysics as it hosts the peak of the thermal radiation of the cold component of the Universe as well as many spectral lines that trace the cycle of interstellar matter 1 – 8 . However, water vapour makes the terrestrial atmosphere opaque to this frequency band over nearly all of the Earth’s surface 9 . Early radiometric measurements 10 below 1 THz at Dome A (80° 22′ S, 77° 21′ E), the highest point of the cold and dry Antarctic ice sheet, suggest that this site may offer the best possible access for ground-based astronomical observations in the terahertz and far-infrared band. To fully assess the site conditions and to address the uncertainties in radiative transfer modelling of the atmosphere, we carried out measurements of atmospheric radiation from Dome A with a Fourier transform spectrometer, spanning the entire water vapour pure rotation band from 20 μm to 350 μm. Our measurements reveal substantial transmission in atmospheric windows throughout the whole band. By combining our broadband spectra with data on the atmospheric state over Dome A, we set new constraints on the spectral absorption of water vapour at upper tropospheric temperatures, which is important for accurate modelling of the terrestrial climate. We find that current spectral models significantly underestimate the H 2 O continuum absorption. Analysis of atmospheric spectra between 20 and 350 μm obtained at Dome A in Antarctica reveals the excellent year-round conditions of this location for Terahertz & Far-IR astronomical observations from ground, usually hindered by water vapour bands.