RealTime Orbit And Clock Estimation Using PANDA Software

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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
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Contents

• Introduction of PANDA software
• Strategy for Real-time POD
• Strategy for Real-time Clock
• Preliminary Results
• Summary

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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 GNSSGEO (COMPASS, GPS)
• POD of LEOs, CHAMP GRACE (Delft University),
  COSMIC (JiaoTong Uni. Taiwan)
• Huge Network (NEIS)
• PPPAmbiguity-Fixing(GFZ, Nottingham Uni)
• ..

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PANDA System Structure
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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 (No2006CB701301)
• Real-time Precise Positioning Service Prototype
  System (863)
• Real-time POD for LEOs (863)

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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

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Parallel Combination

• Save the combined NEQs of the last n-1,n-2, ,1
  hours
• Combined the last hourly NEQ with the saved
  combined NEQs
• Only one combination (red) must be done in
  real-time

Combine hourly NEQs Time-Consuming

• Time-Saving
• Fast restart with saved (combined) NEQ

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Orbital Boundary Constraints
Juncture
Osculating orbital elements
Connected
Not connected
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Solution with the Constraints
NEQs
Juncture constraint
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Stratgy For RT Clocks

• Two approaches are developed
• Estimate SatClock Epoch-by-Epoch(1hz)
• Estimate SatClock Difference between Epoch

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Preliminary Results
Test Network
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
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Result of RT-POD vs IGS Finals
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Result of RT-POD
Difference between calculated real-time orbits
(Hourly predicted orbits) and IGS final products
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Result of RT-CLK vs IGS Finals
RMS values of the difference between the
calculated SatClock and IGS final products over
the period day 198-203 of year 2006
CPUT per epoch on IBM T60 notebook
Statistics of the RMS values
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Performance of the RT Production
Quality of the Real-time SatClock and SatOrbit
for the day of year 2006
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PPP Based on the RT Production
Epoch by Epoch WUHN Station RMS N 2.87cm E
3.23cm U 7.96cm
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Summary

• Real-time POD, 5cm
• Real-time Clock, 0.18ns
• PPP with the Products, 5, 10 cm

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Thanks For Your Attention !