1. Real-Time Orbit And Clock Estimation Using PANDA Software Shi C, Lou YD, Zhao QL, Liu JN GNSS Research Center, Wuhan University, China IGS Analysis Center Workshop 2008 2-6, June 2008, Miami, Florida, USA

2. Contents Introduction of PANDA software Strategy for Real-time POD Strategy for Real-time Clock Preliminary Results Summary

3. Introduction of PANDA PANDA : Positioning And Navigation Data Analyst To derive possible information from GNSS/SLR/ VLBI data in real-time and post-mission Developed at Wuhan University since 2001 Current Applications –POD of GNSS&GEO (COMPASS, GPS) –POD of LEOs, CHAMP GRACE (Delft University), COSMIC (JiaoTong Uni. Taiwan) –Huge Network (NEIS) –PPP+Ambiguity-Fixing(GFZ, Nottingham Uni) –…..

4. PANDA System Structure

5. New Development: Real-Time PPP Based Positioning Service System –Real-time GPS orbits –Real-time GPS Satellite Clock Offsets –Precise Point Positioning Funded by –the Program 973 (No:2006CB701301) –Real-time Precise Positioning Service Prototype System (863) –Real-time POD for LEOs (863)

6. The Strategy For RT-POD Two Steps: Generate NEQs of short ARCs Combine NEQs to estiamte orbits Key Issues: Ambiguity-Fixing Weight of predicted orbits Constrained Parameter: Orbit boundaries Ambiguities ZTD, ERP

7. Parallel Combination Combine hourly NEQs Time-Consuming 1.Save the combined NEQs of the last n-1,n-2, …,1 hours 2.Combined the last hourly NEQ with the saved combined NEQs 3.Only one combination (red) must be done in real-time Time-Saving Fast restart with saved (combined) NEQ

8. Orbital Boundary Constraints Juncture Connected Not connected Osculating orbital elements

9. NEQs: Juncture constraint: Solution with the Constraints

10. Stratgy For RT Clocks Two approaches are developed: Estimate SatClock Epoch-by- Epoch(1hz) Estimate SatClock Difference between Epoch

11. Preliminary Results The distribution of the 70 IGS stations for Real time satellite orbit determination (70stations) Rinex data are inputted as stream through simulated real-time model Test Network

12. Result of RT-POD vs IGS Finals Max （ cm ） Min （ cm ） Mean （ cm ） Radial6.02.74.1 Cross6.53.14.0 Along10.64.67.3 Mean7.53.65.4

13. Result of RT-POD Difference between calculated real-time orbits (Hourly predicted orbits) and IGS final products

14. Result of RT-CLK vs IGS Finals Statistics of the RMS values max(ns)min(ns)mean(ns) 1980.300.040.13 1990.360.100.22 2000.380.070.16 2010.310.070.18 2020.300.120.19 2030.410.070.21 mean0.18 CPUT per epoch on IBM T60 notebook RMS values of the difference between the calculated SatClock and IGS final products over the period day 198-203 of year 2006

15. Performance of the RT Production Quality of the Real-time SatClock and SatOrbit for the day of year 2006

16. PPP Based on the RT Production Epoch by Epoch WUHN Station RMS: N: 2.87cm E: 3.23cm U: 7.96cm

17. Real-time POD, 5cm Real-time Clock, 0.18ns PPP with the Products, 5, 10 cm Summary

18. Thanks For Your Attention !