A technique for routinely updating the ITU-R database using radio occultation electron density profiles
A technique for routinely updating the ITU-R database using radio occultation electron density profiles
复制标题
DOI：
10.1007/s00190-013-0648-x
复制
发表时间：
2013-06
影响因子：
4.4
通讯作者：
C. Brunini;F. Azpilicueta;B. Nava
中科院分区：
文献类型：
--
作者：
C. Brunini;F. Azpilicueta;B. Nava
国际参考电离层或NeQuick等公认和广泛使用的电离层模型通过与F2峰参数（电子密度和高度）相关的分段剖面描述了电子密度随高度的变化。这些参数的准确值是至关重要的，从这些模型中检索可靠的电子密度估计。当无法直接测量这些参数时，模型使用1960年代初建立的所谓ITU-R数据库计算参数。本文介绍了一种技术，目的是定期更新ITU-R数据库使用无线电掩星电子密度剖面来自GPS测量收集的低地球轨道卫星。在使用之前，这些无线电掩星剖面通过拟合电子密度模型来验证。一个重新加权最小二乘算法是用来降低权重不可靠的测量（偶尔，整个配置文件），并retrieveandvalues-连同他们的误差估计-从配置文件。这些值用于每月更新数据库，该数据库由两组类似ITU-R的系数组成，可以很容易地在IRI或NeQuick模型中实现。利用宇宙学/FORMOSAT-3使命小组向社区提供的无线电掩星电子密度剖面图对该技术进行了测试。在高和低太阳活动条件下对至点和春分季节进行了测试。用最小二乘法估计得到的结果图的全局平均误差为F2峰电子密度（相当于估计参数值的7%）和高度（2%）的2.0 ~ 5.6 km之间。
Well credited and widely used ionospheric models, such as the International Reference Ionosphere or NeQuick, describe the variation of the electron density with height by means of a piecewise profile tied to the F2-peak parameters: the electron density,, and the height,. Accurate values of these parameters are crucial for retrieving reliable electron density estimations from those models. When direct measurements of these parameters are not available, the models compute the parameters using the so-called ITU-R database, which was established in the early 1960s. This paper presents a technique aimed at routinely updating the ITU-R database using radio occultation electron density profiles derived from GPS measurements gathered from low Earth orbit satellites. Before being used, these radio occultation profiles are validated by fitting to them an electron density model. A re-weighted Least Squares algorithm is used for down-weighting unreliable measurements (occasionally, entire profiles) and to retrieveandvalues—together with their error estimates—from the profiles. These values are used to monthly update the database, which consists of two sets of ITU-R-like coefficients that could easily be implemented in the IRI or NeQuick models. The technique was tested with radio occultation electron density profiles that are delivered to the community by the COSMIC/FORMOSAT-3 mission team. Tests were performed for solstices and equinoxes seasons in high and low-solar activity conditions. The global mean error of the resulting maps—estimated by the Least Squares technique—is betweenandelec/mfor the F2-peak electron density (which is equivalent to 7 % of the value of the estimated parameter) and from 2.0 to 5.6 km for the height (2 %).