Abstract
The satellite clock prediction is crucial to support real-time global satellite precise positioning services. Currently, the clock prediction for the Chinese BeiDou navigation satellite system (BDS) is still challenging to satisfy the precise positioning applications. Based on the exploration of existing prediction models, an improved model combing the spectrum analysis model (SAM) and the least-squares support-vector machine (LS-SVM) is proposed especially for BDS-2/3 satellites. Considering satellite-specific characteristics, the parameters of the LS-SVM method are optimized satellite by satellite, including input length, regularization and kernel parameters. The improved model is evaluated by comparing the predicted clocks of existing methods and the improved model. The bias of the predicted clock offsets are within ±1.0 ns for most medium Earth orbits (MEOs) over three hours employing the improved model, which is better than that of the existing methods and can be applied for several real-time precise positioning applications. The predicted clock offsets are further evaluated by applying clock corrections to precise point positioning (PPP) in both static and kinematic modes for 10 international GNSS service (IGS) Multi-GNSS Experiment (MGEX) stations, including five stations in the Asia-Pacific region. According to the practical engineering experience, 2 dm and 5 dm are defined for static and kinematic PPP, respectively, as a convergence threshold. Then, in the static PPP, the improved model is demonstrated to be effective, and positioning accuracies of some stations obtain more than 15% improvements on average for each direction, which enables them to get sub-decimeter positioning, especially in the Asia-Pacific region. In the kinematic PPP, the improved model performs much better than the others in terms of both the convergence time and the positioning accuracy. The convergence time can be shortened from 1.0 h to below 0.5 h, while the positioning accuracies are enhanced by 16.3%, 10.8%, and 18.9% on average in east, north, and up direction, respectively.
Highlights
The Chinese BeiDou navigation satellite system, abbreviated as BDS [1], has finished its regional system BDS-2 consisting of 14 satellites in 2012, which provides positioning, navigation, timing, and short message communication services for Asia-Pacific users
We will focus on an improved clock prediction method for all BDS-2 satellites and most BDS-3 medium Earth orbits (MEOs), since the MEO satellite is the backbone type of BDS-3, which has better orbit and clock products than geostationary earth orbits (GEOs) and inclined geosynchronous orbits (IGSOs), due to its favorable observation geometry
The current BDS constellation consists of GEO, IGSO, and MEO satellites, which are equipped with a rubidium atomic frequency standard (RAFS) for BDS-2, and a new-generation high-quality rubidium clock and passive hydrogen masers (PHMs) for BDS-3 (Table 1)
Summary
The Chinese BeiDou navigation satellite system, abbreviated as BDS [1], has finished its regional system BDS-2 consisting of 14 satellites in 2012, which provides positioning, navigation, timing, and short message communication services for Asia-Pacific users. With the great efforts of international GNSS service (IGS) and international GNSS monitoring and assessment service (iGMAS), several types of precise orbit and clock products for BDS satellites are provided to satisfy various positioning demands with different accuracies [5,6,7,8]. Among these products, the ultra-rapid product is generated for possible real-time applications by calculating orbits and clocks over the 24 h.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
