利用国内VLBI网跟踪大椭圆轨道卫星

2004年7月,昆明VLBI站经过改造,由上海、乌鲁木齐和昆明站组成的中国VLBI网(CVN)采用统一的MARK4格式编制器和CVN硬盘记录系统,对大椭圆轨道卫星“探测1号”的2圈轨道的共同可视弧段进行了跟踪观测．软件相关处理程序已成功地用于检测卫星遥测信号的干涉条纹和数据相关处理．采用基于条纹幅度的加权最小二乘条纹拟合方法,获得了卫星VLBI观测量及其精度估计,完成了卫星VLBI观测量的3基线闭合误差检验．应用河外射电源校准方法和多频点相位校正信号提取方法,进行了台站钟差和仪器延迟等系统误差改正．经系统差改正后的卫星VLBI观测量序列已用于“探测1号”卫星的轨道确定．

VLBI Tracking of Highly Elliptical Orbit Satellite with Chinese Domestic Network

VLBI technique has been playing an important role in the precise tracking of deep space probes in the past decades. As the China's furthest satellite launched to date with its 12Re apogee height, the Tance-1 satellite is a good candidate to demonstrate the potential application of VLBI technique for near-Earth space satellites tracking. With participation of Shanghai, Urumqi and Kunming stations, Chinese VLBI network (CVN) conducted an experiment to track the Tance-1 satellite for 2 sequential orbital periods in July 2004. After upgrade of Kunming station, MARK4 formatters and CVN hard disk recording systems, which developed by Shanghai Astronomical Observatory, have been adopted at all 3 stations during this experiment. Software cross-correlation programs were used for fringe check of satellite's telemetry signals and data cross-correlation. Based on weighted least square fringe-fitting algorithm, satellite VLBI delay and rate measurements were acquired. For 0.5s integration time, satellite VLBI delay precision is about 6ns and rate precision is about 2ps/s for Shanghai-Urumqi baseline, while the other 2 baselines have relatively larger measurement errors due to smaller antenna aperture of Kunming station. Three baselines closure test on satellite delay and rate measurements was carried out, which indicated that delay and rate closure errors were consistent with measurement errors. Stations clock offsets and instrumental delays were corrected by calibration of quasars observation and multiple tones Pcal signal extraction method. Corrected data have been applied for orbit determination of the Tance-1 satellite.