tailieunhanh - Sensitivity limit of the vatly radio telescope: Observing the moon

The Moon has been observed using the VATLY radio telescope at frequencies of and MHz in order to study the behaviour of the instrument in a domain of flux density close to the limit of its sensitivity. Drift scans have revealed a Moon flux density of ± kJy corresponding to a Moon black body temperature of 207±40 K. From these results, a limit sensitivity of ∼ 300 Jy has been inferred in agreement with earlier coarser estimates. | Communications in Physics, Vol. 24, No. 4 (2014), pp. 371-380 DOI: SENSITIVITY LIMIT OF THE VATLY RADIO TELESCOPE: OBSERVING THE MOON NGUYEN THI PHUONG, NGUYEN THI THAO, PIERRE DARRIULAT, PHAM NGOC DIEP, DO THI HOAI, PHAM THI TUYET NHUNG, AND PHAM TUAN ANH Department of Astrophysics (DAP), Vietnam National Satellite Center (VNSC), Vietnam Academy of Science and Technology (VAST), 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam E-mail: ntphuong02@ Received 10 November 2014 Accepted for publication 22 December 2014 Abstract. The Moon has been observed using the VATLY radio telescope at frequencies of and MHz in order to study the behaviour of the instrument in a domain of flux density close to the limit of its sensitivity. Drift scans have revealed a Moon flux density of ± kJy corresponding to a Moon black body temperature of 207 ± 40 K. From these results, a limit sensitivity of ∼ 300 Jy has been inferred in agreement with earlier coarser estimates. I. INTRODUCTION The Moon is known to be a strong radio source. At the limit of the ability of our telescope, it is a convenient target for the study of its sensitivity. Its radio emission has been studied in detail in the third quarter of the past century [1]. At infrared wavelengths there are variations correlated with the lunar phase which are due to solar heating. At centimetre wavelengths such variations are nearly negligible. This is because radio emission (which is thermal) arises from below the surface, underneath the regolith, where the rock is heated by conduction and the variations lag behind solar heating. Earlier studies of the performance of the VATLY radio telescope [2, 3], including observations of the Crab (Taurus A) and measurements of fluctuations of the antenna temperature during quiet nights, have suggested that the limit sensitivity of the instrument would be a few hundred Jansky, mostly limited by man-made radio-frequency interferences .