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The Qujing Incoherent Scatter Radar: System Description and Preliminary Measurements Zonghua Ding*, Jian Wu, Zhengwen Xu, Bin Xu and Liandong Dai

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The Qujing Incoherent Scatter Radar: System Description and Preliminary Measurements Zonghua Ding*, Jian Wu, Zhengwen Xu, Bin Xu and Liandong Dai Ding et al. Earth, Planets and Space (2018) 70:87 https://doi.org/10.1186/s40623-018-0859-8 FULL PAPER Open Access The Qujing incoherent scatter radar: system description and preliminary measurements ZongHua Ding*, Jian Wu, ZhengWen Xu, Bin Xu and LianDong Dai Abstract The Qujing incoherent scatter radar (QJISR), the frst one in China with the geographic location (25.6°N, 103.8°E), was brought into operation since the spring of 2014. The QJISR was a mono-static pulsed radar working in the operating frequency 500 MHz, the peak power 2 Megawatt, and a 29-m steerable parabolic dish. This paper mainly presents the basic confguration and implementation of QJISR, including the antenna, transmitter, receiver, signal processing, and data analysis. Some preliminary observation results are also reported including the raw echo, power spectra, and its ionospheric parameters: electron density, electron temperature, ion temperature, and drift velocity. Keywords: Incoherent scatter radar, Ionosphere, Echo profle, Power spectra, Electron density, Electron temperature, Ion temperature Introduction than ten ISRs in the world, which are mainly constructed Te incoherent scatter radar (ISR) owns some unique in America and the Northern Europe (European Incoher- advantages including the wider coverage and simulta- ent Scatter Scientifc Association, EISCAT) separately neous measurements of multi-parameters, which pro- (Evans 1969; Huuskonen et al. 1987; Kelly et al. 1995; vides an outstanding opportunity to investigate the Wannberg et al. 1997; Ya and Zhivolup 2013). In Asia, the ionospheric phenomena and its physical process. Gor- middle and upper atmosphere (MU) radar was completed don (1958) proposed to use the Tomson scatter of free at Shigaraki (34.8°N, 136.1°E) in 1984 (Susumu et al. 1984) electron to sound the ionosphere on the ground by the and had played an important role in the research of mid- powerful radar. In the same year, Bowles (1958) success- dle and upper atmospheric dynamics in Japan. At pre- fully carried out the frst incoherent scatter experiment sent there is no ISR available in the low latitude of Asia, using a radar with peak power 6 MW and central fre- in which the ionosphere has some unique characteristic quency 41 MHz. Bowles’ results found approximately the compared with the American sector such as the known expected amount of power scattered from the electrons east–west longitudinal diferences (Zhao et al. 2013). Te but one much narrower the spectral width, which implies southwest of China is located in the northern crest of that the scatter is not fully independent since the heavier the equatorial ionization anomaly (EIA) and near to the and slower ions are controlling the scattering spectral. Qinghai–Tibet plateau, in which some important science Afterward, the ionospheric incoherent scatter technique cases have not completely resolved including the evolu- is widely used in the world (Evans 1970). tion of EIA and the coupling between the atmosphere As the earliest ISR, the Arecibo (Ioannidis and Farley and ionosphere. 1972) and Jicamarca (Farley 1991) radars started the rou- Supported by the Space Weather Monitoring Meridian tinely operation since 1962. Nowadays, there are more Project of China (Wang 2010), China Research Institute of Radio-wave Propagation (CRIRP) started the con- struction of Qujing incoherent scatter radar (QJISR), *Correspondence: [email protected] the frst one in the mainland of China, in January 2008. China Research Institute of Radio-wave Propagation, 36 Xianshan Road, Chengyang District, Qingdao 266107, China After more than 6 years of efort, CRIRP completed the © The Author(s) 2018. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creat​iveco​mmons​.org/licen​ses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Ding et al. Earth, Planets and Space (2018) 70:87 Page 2 of 13 construction and started the routine operation from the ionosphere, parts of which are detected by the radar March 2014 (Ding et al. 2014a). Te QJISR is located receiving antenna. Te received RF signals are band- in Zhanyi county (25.6°N, 103.8°E, with the altitude of pass-fltered and low-noise-amplifed in the analogue 2040 m), Yunnan Province, China. Te geomagnetic lat- front end and then transferred to the back-end receiver itude is 14.3°N, which is just near to the northern crest located in the control room. Here the RF signal is ampli- of EIA. Te QJISR is one of the key instruments in the fed and down-converted to the intermediate-frequency Meridian Project which consists of diverse ground-based (IF) 30 MHz with the bandwidth 5 MHz. Te IF signals remote sensing facilities aligned near the longitude 120 oE will be digitized, processed, and stored by the signal pro- for space environment monitoring and forecasting. cessor. And the echo profle and power spectrum of the Tis paper presents a detailed technical description of ionosphere are output to the data terminal computer, the QJISR system and its preliminary observations for the from which the ionospheric parameters including the frst time. electron density, electron and ion temperature, plasma drift velocity can be derived. Binary phase codes includ- QJISR technical description ing the 13-bit Barker code and 16-bit alternative code are Te QJISR is a 500-MHz mono-static pulse-modulated utilized for pulse compression by which the signal-to- radar with a 29-m fully steerable parabolic dish and a noise ratio can be improved with better range resolution. 44-m radome. Te technical parameters are listed in Te sequence of 13-bit Barker code is 1,1,1,1,1,− 1,− 1,1, Table 1. Te overall block diagram is presented in Fig. 1. 1,− 1,1,− 1,1. Here ‘1’ and ‘− 1’ represent the phase 0 and Except that the transmitter is imported from USA, all 180, respectively. And the 16-bit alternative code is the the other subsystems are designed and manufactured in same to that used by EISCAT (Lehtinen and Haggstrom China. 1987; Lehtinen and Huuskonen 1996; Sulzer 1993; Mark- Te operation process of the QJISR can be summarized kanenet al. 2008). as follows. Te phase-modulated pulse is generated by Since there is a lightning rod and a small steel plate a direct digital synthesis (DDS) exciter unit and then is used for the elevator at the top of the radome, the maxi- mixed with the reference oscillation frequency (30 MHz) mal elevation cannot be set to 90° so as to avoid the to be up-converted to radio frequency 500 MHz with strong refections. Te minimal elevation is set to 10° to the power level of 10 dBm, which will act as the signal avoid the infuence of clutter from the ground and moun- to excite the subsequent power amplifer. Te exciter sig- tain refection. nal is frst amplifed by a solid-state amplifer to about 100 w and then amplifed by the pulsed klystron to the Antenna high power of 2 MW. Te RF output power from the Figure 2 shows the radome with the diameter of 44 m and transmitter goes through the wave guide, azimuth and the parabolic dish with the aperture of 29 m. Te radome elevation knot, T/R switch, and orthogonal polarizer, and is made of organic reinforced plastics and consists of fnally reaches the feeder, where the RF signal is radiated about 1600 honeycomb-like sub-plates with the thickness into the ionosphere. Te radio signal will be scattered by 0.2 m. Te radio attenuation of the radome is estimated be as 0.3 dB in 500 MHz. Te antenna is a Cassegrain- type parabolic dish of which the total gain is about 41 dB. Figure 3 shows the measured antenna diagram, from Table 1 Technical specifcations of the QJISR which the frst side lobe − 17.58 dB and the 3 dB beam Item Specifcations width can be known. A calibration tower about 3 km away is used to perform the antenna pattern test and Frequency 500 MHz calibration. Peak power 2 MW RF duty cycle 5% ≤ Transmitter System temperature 150 K Figure 4 shows the overview of the transmitter, which Pulse width 20–500 μs is designed and manufactured by the Diversifed Tech- Pulse repetition period 1–20 ms nologies Inc, USA. It consists of the pre-amplifer, the Modulation type 13-bit Barker, 16-bit Alternative code cathode-modulated pulsed klystron, solid-state modula- Antenna Parabolic dish with the 29 m aperture tor, capacitor bank, high voltage–power supply, voltage Antenna gain 41 dB regulator and distribution box, water-cooling manifolds, Side lobe 17.5 dB (frst) three-port circulator, harmonic flter, monitoring and Beam width 1.3° controlling equipment. For safety, all the components Slew rate 3º/s (elevation),5º/s (azimuth) with high voltage are stored inside the oil tank. Te Ding et al. Earth, Planets and Space (2018) 70:87 Page 3 of 13 Fig. 1 Overall block diagram of the QJISR Fig. 2 Radome (left) and the parabolic dish (right) water-cooling manifolds perform the real-time monitor- used to protect the klystron from the refected power sig- ing of the water temperature, pressure and fow. Once nal. Te directional coupler acts as a waveform and power any faults occur, the high-voltage system is shut down monitoring of the output RF signal. Te harmonic flter is and the alarm information is shown immediately in the used to flter out the harmonic signal from the klystron computer touch screen.
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