Phase Calibration Of The All Sky Meteor Radar Located At Wuhan

Meteor radar have been used for the observation for over 50 years.The observed objects of the meteor radar during the initial stages are mainly the meteor shower and its correlative astronomic issues.With the development of radar techinque ,while the data storage and analysis algorithms were possible now, meteor radar was widely used in the study of atmospheric dynamics including atmospheric average wind fields,atmospheric tides and atmospheric planet waves.It was within the renewed interest in the observation of dynamics in meteor regions,meteor radar became one kind of important spatial sounding techniques.Last decade,with the environment of signifacantly improved technology, all sky meteor radar system with wide beam and isotropic receivers was developed,which are capable of seeing the meteors over the whole sky.Moreover,the latest meteor radar system can find the parameters of meteor regions including the winds ,temperatures and pressures. The all-sky meteor radar recently developed was the newest generation of meteor radars, and the Wuhan meteor radar (WHMR) installed at the beginning of 2002 is the first meteor radar system in China. At present, the main objects observed by WHMR are the atmospheric dynamics in the meteor regions, these some extremely typical research topics including atmospheric averaging wind fields, atmospheric tides and atmospheric planet waves.Interferometric radar use phase information recorded at the receiving antennas to determine meteor locations,so errors in antenna placement and instrumental phase differences caused by various factors can degrade the spatial location estimation.It is therefore critical to have an accurate assessment of the phase offsets in the radar system in order to accurately determine the direction of arrival.This thesis attempted to estimate the WHMR system phase offsets and calibrate the phase error using the raw data of meteor echoes.Furthermore,we also use the data after calibration to study the statistical characterization of meteor distribution and wind field over Wuhan.First, we can estimate the phase differences of the meteor echo between each receiver pairs with data collected by WHMR,take account of the receiver pairs geometries to form the linear equation matrix, solving for the phase bias between each receiver pairs in the least-squares sense, and finally find the location of meteor echoes after calibration. Compare with the conventional method, this method can use the history data to find the system phase bias, without the need for additional hardware. It can routinely use for off-line to correct data collected using the bias estimated before. We take the data between April 2004 to June 2004 as an example, and the result shows the system bias show very small variations during this period. The data calibrated using this method shows a more consistent height distribution in terms of number of echoes with the same meridian.Moreover, we use the raw data,which had been calibrated using the method mentioned above, from January 2005 to December 2005 to study the seasonal characteristics of mean winds and tides in the 80-100km height over Wuhan. Conspicuous features of mean winds include a strong shear in the summer zonal flow, resulting in eastward flows of exceeding 34m/s at the heights of 85-95km. Westward flows occur in a very limited height range. An westward flow appears below 86km in March/April, as well as a weak westward flow occurring above 92km in December. The diurnal tides have strong maximum amplitude in March/April, respectively. The secondary maximum of the diurnal tide appears in November and the minimum appears in winter and summer solstices. The phase advancing in winter before in summer. At each height the diurnal tide shows an phase advance of the meridional component against the zonal component。In brief,this thesis discusses a new method of phase calibration for WHMR,and used the data after calibration to study the statistical characterization of meteor distribution and wind field over Wuhan.The result shows that this new method used in the calibration can remove the phase offset from the radar system. This method can significantly improve the precision of the detection parameters,and get better exertion of the meteor radar. This method can be applied to all-sky meteor radar,and can be generalized to the similar interference radar system.