Radio Quiet Zones in China

Haiyan Zhang*12, Zhijun Chen13, Bin Li4, Maozheng Chen5, Yingxi Zuo6, Min Wang7,

1National Astronomical Observatories, Chinese Academy of Sciences, A20 Datun Road, Chaoyang District, Beijing, 100012, China, hyzhang@bao.ac.cn

2 Key Laboratory of Radio Astronomy of Chinese Academy of Sciences

3zjchen@nao.cas.cn

4Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, China, bing@shao.cas.cn

5Xinjiang Astronomical Observatory, Chinese Academy of Sciences, 150 Science 1-Street, Urumqi, Xinjiang

830011, China, chen@xao.ac.cn

6Purple Mountain Observatory, Chinese Academy of Sciences, 2 West Beijing Road, Nanjing 210008, China, yxzuo@pmo.ac.cn

7Yunnan Observatories, Chinese Academy of Sciences, P.0.Box110, Kunming 650011, Yunnan, China,

wm@yao.ac.cn

Abstract

Several advanced radio telescopes have been or under constructed in China, such as Five-hundred-meter Aperture Spherical radio Telescope (FAST), Chinese Spectral Radio Heliograph (CSRH) and Tianma Radio Telescope (TMRT). To optimize the radio environment in which radio astronomy observations are carried out, different Radio Quiet Zones (RQZs) with definitions and management methods have been established in China. RQZs for FAST, CSRH and TMRT are presented briefly in this paper.

1. Introduction Radio Astronomy Service is a service involving the use of radio astronomy which is based on the reception of radio waves of cosmic origin [1]. Because radio astronomy signals are so weak in comparison to those of other services, radio astronomy observations are highly vulnerable to radio interference from man-made sources. In order to protect the radio environment of the high sensitive radio telescope, radio quiet zones (RQZs) have been implemented by some Administrations. A RQZ is defined as any recognized geographic area within which the usual spectrum management procedures are modified for the specific purpose of reducing or avoiding interference to radio telescopes, in order to optimize the environment in which observations are carried out [2]. In recent ten years, several radio telescopes have been constructed or proposed in China, such as Five-hundred-meter Aperture Spherical radio Telescope (FAST), Chinese Spectral Radio Heliograph (CSRH), Tianma Radio Telescope (TMRT), proposed Qitai 110 meter radio telescope. To protect the radio environment of these advanced modern facilities, different RQZs with definitions and management methods have been established or proposed in China, depending on their specific requirements. Three RQZs in China are introduced below.

Figure 1 FAST model Figure 2 CSRH Figure 3 TMRT

978-1-4673-5225-3/14/$31.00 ©2014 IEEE

2. RQZ around FAST

FAST is a Chinese mega-science project to build the largest single dish radio telescope in the world [3,

4]. Its frequency will cover from 70 MHz to 3 GHz. The first light of FAST is expected in 2016. After about ten year site surveying, FAST site has been finally selected, a depression called as Dawodang located in south Guizhou. The remoteness and sparse population density together with the futility of industrial development potentially benefit the radio environment and the safety of future FAST instruments. A series of radio frequency interference (RFI) measurements were carried out since 1994, the results show that the radio environment of the site is extremely quiet and statistically stable [5]. In order to protect the radio environment around FAST efficiently, an agreement on a RQZ around the site has already been signed by the Chinese Academy of Sciences and local government. The legislation of RQZ had been approved finally by Guizhou government in June 2013. Considering the development of local society, the final size 30 km radius of RQZ, has been decided for compromise. The radio interference threshold level of FAST RQZ is defined at a value of 10 dB less than the radio telescope noise. International Telecommunication Union (ITU) has provided the recommendation ITU-R RA.769-2 which describes different RFI threshold levels for line or continuum observations of Radio Astronomy Service [6]. The protection area is divided into three subsections, radius R ≤ 5 km is named as restriction zone (Fig. 4); 5 km < R ≤ 10 km is the central area, and 10 km < R ≤ 30 km is the remote area, named as coordination zone (Fig. 5). Within the restriction zone, any kind of new transmitters are not allowed to be stationed. Within the coordination zone, operators wishing to station the transmitters are required to coordinate with the operators of the FAST telescope, especially the transmitters operating at FAST bands with power above 100W are forbidden to be stationed in 5 km < R ≤ 10 km area.

Figure 4 Restriction zone around FAST Figure 5 Coordination zone around FAST

3. RQZ around CSRH To understand fundamental processes in the solar eruptive phenomena, it is important to have imaging-spectroscopy over centimetric-decimetric wave range. CSRH in 0.4-15 GHz range with high time, space and frequency resolutions is being constructed to achieve this goal [7]. CSRH is constructing at Zhengxiangbaiqi, Inner Mongolia. The array of CSRH-I in 0.4-2.0 GHz band with 40 4.5m antennas has been established and starts test observations. The 60 2m antennas for array of CSRH-II in 2-15 GHz have been mounted and assembled. The largest base line is 3 km and the field of view is from 0.5 to 7 degree. CSRH is located in a RQZ with 10 km radius. Within this zone, any new transmitters are not allowed to be stationed.

4. RQZ around TMRT

Due to the requirement of deep-space exploration and high-sensitivity radio observations, a new large telescope, Tianma 65 meter radio telescope near Shanghai has been constructed [8]. In October 2012, the telescope successfully performed the testing experiments. The L, S, C and X band receivers have been installed in December 2012, the receivers at higher frequency bands will be considered in near future. In December 2013, the telescope has joined into the Chang’e-3 lunar probe project successfully. Considering the complex radio environment and development of local economy, the range of RQZ around TMRT is limited to 3 km radius. The protection area is divided into two subsections, radius R ≤ 1 km is named as restriction zone; radius 1 km < R ≤ 3

km is named as coordination zone. Within the restriction zone, any kind of new transmitters are not allowed to be stationed. Within the coordination area, the operators of any new transmitters are required to coordinate with the observatory.

5. Conclusion In China, several advanced and modern radio telescopes have been constructed or proposed. From previous experiences, to establish RQZ is mostly effective method to protect the radio environment of radio telescope. The protection regulations of RQZ will apply to fixed, terrestrial transmitters which require licenses, and instruments emitting electromagnetic wave using by industry, agriculture and medicine. Meanwhile, RQZs require considerable effort to maintain after their creation. In China, the radio astronomers will cooperate variously with the local spectrum management office to optimize the radio environment of the radio observations.

6. Acknowledgments

This work is supported by the National Development and Reform Commission of China and the Key Laboratory of Radio Astronomy of Chinese Academy of Sciences. We wish to make special recognition to the diligence and great efforts by colleagues in Observatories of Chinese Academy of Sciences and local spectrum management office, and would also like to apologize for the incomplete coverage of their great contributions to this work.

7. References

1. Radio Regulations, Edition 2012, International Telecommunication Union 2. ITU-R RA.2259, “Characteristics of radio quiet zones”, International Telecommunication Union, 2012 3. R. D. Nan, “Introduction to FAST: five hundred meter Aperture Spherical radio Telescope”, Ground-based and Airborne Telescopes II. Edited by Stepp, Larry M.; Gilmozzi, Roberto., Proceedings of the SPIE, Volume 7012, 2008, pp. 70121E-12. 4. R. D. Nan, D. Li, C. J. Jin, Q. M. Wang, L. C. Zhu, W. B. Zhu, H. Y. Zhang, Y. L. Yue, L. Qian, “Five-Hundred Aperture Spherical Radio Telescope (fast) Project”, International Journal of Modern Physics D, Volumne 20, 2011, pp. 989-1024. 5. B. Peng, J. B. Li, T. Y. Piao, J. M. Sun, R. G. Strom, “Radio Spectral Monitoring Campaign at Proposed SKA Sites in China”, Publications of the Astronomical Society of the Pacific, Volume 120, 2008, pp.625-633. 6. ITU-R RA769-2, “Protection criteria for radio astronomical measurements”, International Telecommunication Union, 2003. 7. Y. H. Yan, W. Wang, F. Liu, L. H. Geng, Z. J. Chen, J. Zhang, “Radio imaging-spectroscopy observations of the Sun in decimetric and centimetric wavelengths”, IAU Symposium, Volume 294, 2013, pp. 489-494 8. X. Y. Hong, S. H. Ye, T. S. Wan, D. R. Jiang, Z. H. Qian, R. D. Nan, N. Wang, Z. Q. Shen, H. B. Zhang, M. Wang, “The development of VLBI in China and its relationship with the EVN”, Proceedings of the meeting “Resolving The Sky - Radio Interferometry: Past, Present and Future”, Manchester, UK, 2012, pp. 12-14