利用COSMIC数据构建的全球垂直TEC图的验证研究

Validation of Global VTEC Maps Constructed Using Data Derived From COSMIC Constellation

在日固坐标系(地磁纬度和地方时)下,累积地方时过去24 h的COSMIC(Constellation Observing System for Meteorology Ionosphere and Climate)观测资料,通过对110～750 km高度范围内的电子密度进行数值积分得到各掩星点的垂直TEC值,进而利用Kriging方法插值产生近实时的全球地方时MAGLat 2.5°×2 h的COSMIC TEC图.利用2008年1月1日至2010年6月30日共30个月的COSMIC数据,逐日构建COSMIC TEC图,将其与全球导航卫星系统服务组织(International GNSS Service,IGS)发布的全球电离层TEC图(Global Ionospheric Maps,GIMs)以及OSTM/JASON-2卫星高度计观测值分别进行比对,证明利用COSMIC掩星资料构建全球电离层垂直TEC图是可行的.

The construction of reliable global maps of vertical total electron content of the Iono- sphere （Vertical TEC or VTEC Maps） is a useful but challenging task. A new technological route to construct global VTEC maps has been raised by us that COSMIC RO data points are collected dur- ing the past 24 hours in the sun-fixed coordinate system （local time and geomagnetic latitude） and then vertical TEC values within height range from 110 km to 750 km are calculated by numerical integration of electron density profiles at these RO points after quality control. At last, ordinary Kriging method is adopted to construct Global COSMIC TEC Maps with a grid resolution of MAGLat 2.5°× 2 h. Comparisons during the interval from DOY （Day of Year） 001, 2008 to 181, 2010 between Global COSMIC TEC Maps and IGS GIMs, from DOY 194, 2008, to 181, 2010 between Global COSMIC TEC Maps and OSTM/JASON-2 observations have been made, and differences are calculated for different seasons, local time and geomagnetic latitudes. It proves that COSMIC TEC Maps have good agreements with IGS GIMs and OSTM/JASON-2 observations, so COSMIC TEC Maps are accurate enough to be used to correct the ionospheric delay in GNSS systems. With further improvement on RO theories and commencement of new RO constellations in future, the quality and quantity of ionospheric RO data will be raised greatly with no doubt. Hence, it will be a much promising technology to apply ionospheric RO data to correct the ionosoheric delav for GNSS svstems.