Dome A Fourier Transform Spectrometer (FTS)
Inside view of the interferometer
The Dome A FTS was first installed in PLATO at Dome A during January 2010, and ran for 3 years. It is a site survey instrument to evaluate the atmospheric transmission from 0.75–15 THz. This broad spectral coverage is particularly important at Dome A, where the extremely cold temperatures lie well outside the tested range of water vapor continuum models. The FTS is a polarizing Martin-Puplett interferometer operated in rapid-scan mode. The two output ports of the interferometer are equipped with different detector/filter combinations, providing a high throughput, low frequency band covering 0.75–3.5 THz, and a lower throughput, high frequency band covering 0.75–15 THz. The resolution for both bands is 10 GHz.
At Dome A, cryogenic cooling of the detectors and calibration loads is not practical due to the large power requirements. Instead, the FTS is equipped with ambient-temperature DLATGS pyroelectric detectors. For calibration, one input port of the interferometer always views a passive reference load on the optics bench, while the second input port alternates between the sky and a second movable passive reference load at outdoor ambient temperature. A complete measurement cycle on load and sky takes 10 minutes.
Schematic of the outdoor calibration subsystem
The interferometer subsystem and detectors were built to specification by Blue Sky Spectroscopy of Lethbridge, Canada, and QMC Instruments in the UK. The data acquisition system and outdoor calibration load assembly were produced at Purple Mountain Observatory in Nanjing. The first of two identical instruments was installed at Dome A in January 2010.
Conference proceedings from the Dome A FTS
- Shi, S.-C., Paine, S., Yao, Q.-J., Len, Z.-H., Li, X.-X., Duan, W.-Y., Matsuo, H., Zhang, Q. , Yang, J., Ashley, M. C. B., Zhao-Hui, S., Zhong-Wen, H., 2012, THz atmospheric transmission measured at antarctic Dome A, 37th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 23–28 Sept. 2012, p. 1–2.
Dome A FTS team
Sheng-Cai Shi (PI), Q.J. Yao, X.X. Li, X.G. Zhang, Z.H. Lin, K.M. Zhou, Q.G. Huang, and J. Yang Purple Mountain Observatory.
Scott Paine, Q.Z. Zhang, Harvard-Smithsonian Center for Astrophysics.
H. Matsuo, National Astronomical Observatory of Japan.
Participating institutions in alphabetical order
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Chinese Academy of Sciences, China |
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Harvard-Smithsonian Center for Astrophysics, USA |
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National Astronomical Observatory of Japan |
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Purple Mountain Observatory, China |