Search

At first, the receiving system of the Tianma 65m radio telescope (TM65m in brief) and its noise characteristics at the L, S, C, and X four frequency bands are described. Then, a few measuring methods of system noise temperature are discussed, and the major factors affecting the noise temperature measurement are analyzed, including the errors caused by the non-linearity, feed network insertion loss, mismatch, and so on. With the Y-factor method the noise temperature of the noise source calibrated in the laboratory is verified, indicating that its accuracy attains ∼0.2K. Finally, the system noise temperatures actually measured at the four frequency bands and an analysis on the result are given.

In this paper the precision of the VLBI tracking delays and the positioning reduction results during the real-time stage of the Chang'E-2 project is statistically analyzed, the application of the positioning reduction to the real-time monitoring of the pivotal arcs of the Chang'E-2 satellite is discussed, the related technical specifications of the experiment of X-band monitoring and control system are estimated and evaluated via the positioning reduction method. Useful methodology and software are prepared as well as practical experience in engineering and technology is accumulated for the follow-on lunar exploration projects of China.

For the first time, a new concept of space VLBI's application is presented, in which space VLBI technique is used to sound ionospheric electron content along the ray path.

This paper briefly introduces the current status of the Chinese VLBI Network (CVN) Project and its astrometric and geodetic goals.

For the first time, a new concept of space VLBI’s application is presented. in which space VLBI technique is used to sound ionospheric electron content along the ray path.

The first VLBI experiment between Shanghai and Effelsberg, West Germany, was carried out at 1430 MHz in November 1981. The observations lasted 54 hours and the Mark II recording system and hydrogen masers were used at both stations. Fourteen extragalactic sources covering a wide range of declination were duly observed. The Shanghai-Effelsberg baseline vector was determined to an estimated formal precision of 2–3 metres and the positions of the sources 1739 + 52 and 1928 + 73, to 0 ″ . 05 − 0 ″ . 08 in each coordinate, with the effects of the ionosphere not removed. The source of 1928 + 73 was found to be double with a component separation of 0 ″ . 0089 .

From March 31 to April 4 and from April 13 to 17, the 1667 MHz OH line of comet Halley was observed in Shaanxi province of China with the 25B radio telescope of Shanghai Observatory and a 128-channel autocorrelation spectrometer of Peking University. The bandwidth of the spectrometer was 625 KHz and the resolution was 4.92 KHz (0.89 km/s). The receiver was frequency-switched with a frequency shift of 197 KHz. In order to improve the signal-to-noise ratio, we accumulated the 1667 MHz profiles of April 13 to 17. According to the synthetic profile, we can summarize the results as follows: 1. (1) The intensity of the absorbed OH flux was calibrated by means of measurements of the 1667 MHz OH line of W12. The observed mean OH flux of 4 days is −2.4 Jy. 2. (2) The measured OH expansion velocity VOh = 0.92 km/s, when the heliocentric distance rh = 1.39 AU. 3. (3) The profile asymmetry may be characterized by the first order moment Δv= 0.20 km/s. 4. (4) The mean OH parent production rate Qp = 1.7 × 1029 mol/s, assuming Hasser's model with the parameters defined in Despois et al.