【正文】 2) Verified and modeled the possibility of using ACEVS to test the change of state of stochastic delays The possibility of using ACEVS to monitor ionosphere is verified in terms of theory. Also it is found that the statistical property of ACEVS is sensitive to the change of the random ionospheric delay, on the basis of modeling the characteristics of ACEVS using a dual frequency GPS receiver. The application conditions of using ACEVS to monitor the variation of TEC extracted by GPS data are preliminarily discussed and analyzed as well. 3) Established a preliminary framework scheme of using GPS to monitor the disturbance of random ionospheric delay. According to ACVES and all other results of the above and the characteristic of the time series observations of GPS, a preliminary framework scheme for monitoring the disturbance of random ionospheric delay using GPS is established. Although this method is proposed for real time monitoring, it can be easily applied to postprocessing of GPS data. The framework scheme based on ACVES can be used to design many practical schemes for monitoring ionosphere variation using a (static or kinematic) dual frequency GPS receiver. 5 A new method of modelling ionospheric delay using GPS data ——Ionospheric Eclipse Factor Method (IEFM) The Ionospheric Eclipse Factor (IEF) and its influence factor (IFF) of Ionospheric Pierce Point (IPP) is present and a simple method of calculating the IEF is also given. By bining the IEF and IFF with the local time t of IPP, a new method of modelling ionospheric delay using GPS data —Ionospheric Eclipse Factor Method (IEFM) is developed. The IEF and its IFF can efficiently bine the different ionospheric models for different seasons according to the diurnal, seasonal and annual variations of ionosphere. The preliminary experimental results show that the correction accuracy of the ionospheric delay modeled by IEFM is very close to that of using the ionosphere free observation to correct directly the ionospheric delay, that is, the precision of using IEFM to model ionospheric delay for single GPS users seems to has a breakthrough improvement and be similar to that of using the corresponding dual frequency GPS data to correct directly the ionospheric delays. The IEFM also suits to model the ionospheric delays for a kinematic based–single GPS receiver embeded in lowearth satellite with high rapid due to its good ability in distinguishing the daytime and nighttime of the earth ionosphere for an IPP. 6 A new strategy of correcting ionospheric delay for highprecision orbit determination for lowearth satellite using a single frequency GPS receiver the APRII scheme, ., Spacebased APR scheme Analyzed the shortings of using the previous methods to divide with high accuracy the earth ionosphere into different layers. Used GPS data to model global ionospheric TEC. Established a high precision grid ionospheric model. Discussed the possibility of finding out some local areas whose ionospheric construction and action have relatively better obvious law with respect to the other areas on a global scale. Designed a scheme for bining GPSgrounded data with GPSspaced data to divide efficiently the ionosphere into some layers. Given the corresponding formula of estimating the precision of the scheme. The preliminary precision estimation a nd the experimental results show the possibility and property of the above idea of dividing ionosphere into different layers according to application requirement and its implementation scheme. Based on the above research, the APRII scheme is presented which is a new and bined method of correcting the ionospheric delays of highprecision orbit determination for