1 BDS GNSS GNSS BDS [1] [2] BDS (GEO) (IGSO) (MEO) GEO MEO BDS BDS ICD (Interface Control Document) [2] [2, 3] GPS WAAS (Wide Area Augme

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1 33 1 Vol. 33, No PROGRESS IN ASTRONOMY Feb., 2015 doi: /j.issn BDS 1, ,2 3 1 ( ) BDS BDS ( ICD ) DOP GEO BDS 50% 60% P173 A 1 (GNSS) (BDS) BDS ( ) ( ) (14DZ ) hxg@shao.ac.cn

2 1 BDS GNSS GNSS BDS [1] [2] BDS (GEO) (IGSO) (MEO) GEO MEO BDS BDS ICD (Interface Control Document) [2] [2, 3] GPS WAAS (Wide Area Augmentation System) [4] BDS GNSS BDS i j P j i = X sat X rcv + c( t i t j ) + ε orb + ε satclk + t Iono + t Trop + t cor + ε j i. (1) P j i X sat X rcv t i t j ε orb ε satclk t Iono t Trop t cor ε j i (1)

3 pcor j = (ε orb + ε satclk ), (2) pcor j j 2.2 (2) (dr, dt, dn) i ε orb = a i dr + b i dt + c i dn (a i, b i, c i ) [5,10] GEO G5 (60 E) G4 (160 E) 1 R, T, N 1 1 (a) GEO4 (b) GEO T N IGSO

4 1 BDS GEO 4 GEO 5 R T N WAAS BDS 2 2 [6] T AS = 1 2 (R A R S ) [(τ A T + τs R ) (τs T + τa R )] + 1 ion (τas τsa ion ) tro (τas τsa tro ) (τ AS G τsa) G (τ AS τ SA ), (3) T AS R A R B τ A T τ S T τ A R τ S R ion ion τ AS τ SA

5 τ AS tro tro τ SA τ AS G τ SA G τ AS τ SA 1 ns [3,7] kalman [4] ε satclk n n Clk sta = (ρ(o) ρ (C) ). (4) n ρ (C) ρ (O) (dx i j dy i j dz i j) ρ i(o) j ρ i(c) j = A dx i j dy i j dz i j dr i = A RT N dt i, (5) dn i A i j ns [5] [2] BDS DOP DOP (5) Q RT Ni = (A T RT Ni P i A RT Ni ) 1 RDOP i = Q RT Ni1,1, T DOP i = Q RT Ni2,2, NDOP i = Q RT Ni3,3. (6) 10 BDS R 4.3 T 26.6 N GNSS BDS

6 1 BDS SatID RDOP T DOP NDOP P DOP SatID RDOP T DOP NDOP P DOP GEO IGSO GEO IGSO GEO IGSO GEO IGSO MEO IGSO MEO Mean BDS (24MEO+3GEO+3IGSO) 3 cowell MEO MEO IGSO GEO MEO 3 IGSO GEO BDS 4

7 m [8] 0.01 m 4 DOP UERE [9] = DOP UERE UDRE 4.1 DOP MEO IGSO GEO R T N 24 h RMS 3 RMS = mean 2 + std 2 mean std 3 20 MEO IGSO GEO 50% R T 10% R N

8 1 BDS MEO-06 MEO-10 IGSO-28 IGSO-30 IGSO-25 IGSO-26 DOP (COV ) RDOP T DOP NDOP P DOP R/T R/N T/N / / / / / / % T N 20% 1 MEO 1 GEO 1 IGSO P DOP 7 7 (a) 6 MEO (b) 26 GEO (c) 28 IGSO SG SS DOP MEO IGSO 7 / P DOP DOP

9 MEO / R 4 cm T 18 cm N 11 cm R 1 cm T 4 cm N 5 cm 8 MEO (a) (b) / 4.2 UDRE UERE (UERE) (UDRE) [2] (dx i j dyj i dzj) i 3 (dx i j dyj i dzj) i ( 4) ( ) ( ) 2 3 UDRE UERE 9 10 UERE UDRE 1 1 UDRE 2 2 UDRE 3 3 UDRE UDRE UDRE UDRE

10 1 BDS UDRE UERE 10 UDRE UERE 5 BDS BDS GEO/IGSO DOP

11 (dx i j dyj i dzj) i T N R 4 BDS MEO IGSO GEO 50% R T 10% R N 20% T N 20% UDRE 60% [1] [2] Cao Y L, Hu X G, et al. Sci China Phys Mech Astron, 2012, 55: 1307 [3] Zhou S S, Cao Y L, et al. Sci China Phys Mech Astron, 2012, 55: 2290 [4] Yeou-Jyh Tsai. Dissertation. Stanford: Stanford University, 1999: 175 [5],,. GPS ( ). :, 2004: 97 [6],., 2004, 22(3): 219 [7] Zhou S S, Hu X G, Wu B, et al. Sci China Phys Mech Astron, 2011, 54: 1089 [8] Karl S, Zeta AI, Peter S, et al. ION GPS Utah: ION, 2001: 2334 [9] Jiao W H, Ding Q, Li J W, et al. Sci China Phys Mech Astron, 2011, 41: 521 [10] Cai C L, Li X H, Wu H T. Sci China Ser G-Phys Mech Astron, 2009, 52: 310 The Method for Real-time Wide Area Differential Corrections of BDS with Inter Satellite Links CAO Yue-ling 1,2, HU Xiao-gong 1, ZHOU Shan-shi 1, LIU Li 3, WU Xiao-li 3, SU Ran-ran 3, CHANG Zhi-qiao 3, HE Feng 3, WU Bin 1 (1. Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai , China; 2. Graduate University of Chinese Academy of Sciences, Beijing , China; 3. Beijing Global Information Application and Development Center, Beijing , China) Abstract: Real-time wide area differential corrections ensure BDS authorized users with high-accuracy navigation service. A new method for introducing time synchronization observations for the correction estimation is introduced, the performance of two approaches with one- or four-dimensional correction parameters are compared. Results show that for

12 1 BDS 133 one-dimensional approach, the correction accuracy will decrease when the orbital errors are large. Therefore it is not suitable for the situations such as quickly orbit determination recovery after satellite failure or maneuver. While for four-dimensional approach, the stability and precision of ephemeris and satellite clock parameters are seriously affected by the limited regional monitoring network. Considering that the Inter satellite links will be setup to support auto-navigation for the global BDS system, the separation of orbital and satellite clock errors is discussed with inter satellite links. Simulation processing results show that the orbital errors in ephemeris may be effectively solved with inter satellite link observations, and propagation error may be reduced by 50%. Compared with one-dimensional approach, the performance of four-dimensional approach is also improved by 60% in the area lacked monitor stations. Key words: equivalent satellite clock error; separation of orbital and clock error; inter satellite links; DOP; UDRE

MHz 10 MHz Mbps 1 C 2(a) 4 GHz MHz 56 Msps 70 MHz 70 MHz 23 MHz 14 MHz 23 MHz 2(b)

MHz 10 MHz Mbps 1 C 2(a) 4 GHz MHz 56 Msps 70 MHz 70 MHz 23 MHz 14 MHz 23 MHz 2(b) 2011 32 ANNALS OF SHANGHAI OBSERVATORY ACADEMIA SINICA No. 32, 2011 1,2,3 1 2,3 2,3 2,3 2 1 1 ( 1. 200030 2. 100094 3. 100094 ) V474 1 (CEI) ( VLBI ), CEI 100 nrad ( 50 km) CEI 10 100 km 2 2 2 CEI [1]