Near Real-time Monitoring And Inverting TEC Of Ionosphere Based On Kalman Filter

Ionosphere is an important part of terrestrial space environment. The study ofionosphere can expand our knowledge of integral activities of solar and terrestrial spacesystem and further provide better service for human space activities; therefore, the study ofionosphere is of great significance. In recent years, with the increasing of human spaceactivities and satellite communication systems, it has a strong demand for monitoring andInverting of various variation characteristics and laws (especially the temporal and spatialvariation) of the ionosphere.At present, utilizing GPS to calculate the Total Electron Content (TEC) has become theprimary technology to monitor the ionosphere activities. The continuous operating GPSobserving station networks of diverse scales and densities both at home and abroad providethe platform for local, regional and global ionosphere research. Since1998, the InternationalGNSS Service (IGS) has began to broadcast Global Ionosphere Map everyday (GIM),however, the ionosphere IONEX Files issued by the IGS Analysis Centers do not have highresolving capability both in time and space. Since there are few IGS observing stations inChina, its accuracy is not desirable; besides, IONEX Files is a non-GPS user interface forusing IGS ionosphere products rather than the specific format of GPS. So we need to set up aregional GPS observation station network and set up a ionosphere model based on real-timeGPS observation data to monitor, broadcast/forecast the ionosphere activities, which canprovide single frequency GPS users the delayed and corrected information of ionosphere.Under this background, selecting4GPS double frequency observation station networks,adopting the kalman filtering to monitor the real-time the temporal and spatial variation ofionosphere, and choosing the kriging method that is frequently-used in geographic statistics toreconstruct the ionosphere TEC map at Xi’an in this paper.The main work and achievements of the paper are as follows:1. The TurboEdit algorithm is introduced in this paper which detected and repaired cycleslips in GIPSY, and the detection conditions of cycle slip is analyzed to TurboEdit algorithm.Moving average is used to replace overall average of all data before each epoch in theWide-lane ambiguity, at the same time Geometry-free Combination is improved bydifferenced in the adjacent epoch. Experimental results show that the improved algorithm ismore effective than TurboEdit algorithm for the problem of blind spots in TurboEditalgorithm and high cycle slip rates and bad multipath condition.2. Using the pseudo range method to extract revised carrier phase extracting TECPso as to real-time extract the slant path ionosphere in this paper. The result shows that the revisedionosphere TEC well coincides with slant path ionosphere TECPextracted from pseudo rangeobservation, which is able to reflect the trend of ionosphere TECPextracted from pseudorange observation, and the revised ionosphere TEC data are more smooth and centralized.Using the Chebyshev polynomials to interpolate the GPS Satellite orbits and calculates thecoordinates of ionosphere puncture points in this paper.3. Using the Kalman filtering to estimate ionosphere mode coefficients of every epoch aswell as the hardware delay of observation stations and satellites in this paper., achieving thepurpose of real-time monitoring of the ionosphere activities. Compared the directly calculatedionosphere TEC of GPS observation data with the vertical TEC obtained by kalman filteringalgorithm the result shows that the latter can reflect the real-time change of ionosphere TECactivities.4. It applies kriging method to reconstruct the ionosphere TEC map in Xi’an region andverifies the calculated result through the final TEC products provided by CODE analysiscenter. The result shows that its calculated result in this paper is basically the same with thatof the CODE.