This group researches methods of precise orbit determination for a spacecraft and their applications. These applications include monitoring the motion and variation of the Earth as a whole and in its component parts (the atmosphere, oceans, and the Earth's crust), as well as the orbit design of spacecraft related to the national economy and national defense. The main directions of our current research are: (1) the synthetic processing of many satellites, many stations, and many kinds of observational data, including the method of calculation, the mechanical model, and the establishment of an appropriate software system; (2) space-based GPS meteorology, including orbit design for the LEO satellite, in order to make the GPS's occultation position unchangeable, and the weather monitoring in the flood or rainstorm disaster areas. The research group is lead by Prof. Xiaogong Hu .

Main research progress:

(1) The problem of occultation position control in the GPS/LEO satellite: this problem was first solved by using orbit commensuration, and will thus benefit the study of atmospheric structure and weather monitoring for some areas, such as the ocean, desert, and regions difficult to travel to by foot.
(2) Contributions to the Earth’s dynamical oblateness from the mass transfer which results from oceanic circulation change: the oceans, when considered as a fluid, were found to make notable contributions to the unusualchange of the Earth’s dynamical oblateness on non-seasonal time scales. This effect was first observed using SLR techniques in 1997.
(3) The newest plate motion model NNR-ITRF96VEL was derived based on the velocity field of ITRF96, and better reflects the kinetic characteristics of the global plates. We have also put forward the idea that there exists global rotation of the ITRF96 frame presently maintained by the IERS, and that this is not concordant with the definition of the Conventional Terrestrial Reference Frame (CTRF).
(4) We proposed that the criteria of whether the posterior residual satisfies a Gaussian distribution can be used to judge the solution quality of data analysis results in space geodesy. In addition, we have quantitatively evaluated the solution quality of results from space geodesy data analysis with statistical quantities such as the Pearson χ2 and higher order moments.
(5) Data from the ocean altimetry satellite TOPEX was used to monitor the global sea level change from January 1993 to May 1999, in which various sources of small measurement error were considered. A mean value of 2.0±0.2mm/year for the global rate of sea level change was derived.
(6) The software used to process space geodesy data has been improved greatly, and significant progress made in our ability to process observational data taken using new space-based techniques such as SLR, GPS, and PRARE. The accuracy of orbit determination, as well as data processing are all approaching international advanced ranks.
(7) Proofread of the predicted accuracies of some SLR satellite orbits has completed. Our conclusions were that if the Chinese local SLR network is used to track a satellite with a height of order 800km, the prediction accuracy is good to 300m per day.

Leading Professor: Xiaogong Hu

Group Members :

Faculty: Yanling Chen(ssociate professor),  Xiaojun Dong(professor),Xiaogong Hu(professor), Cheng Huang(professor),  Yong Huang(ssistant professor), Shuhua Ye(professor,Academician of CAS).