Some Thoughts on L1CAL2C Derived TEC - PowerPoint PPT Presentation
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Some Thoughts on L1CAL2C Derived TEC
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Examine Ithaca data from two consecutive days using Brady's C receiver and ... Difference in consecutive. measurements of TEC by D(df) TOA TEC with Recursive Filter ... – PowerPoint PPT presentation
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Title: Some Thoughts on L1CAL2C Derived TEC
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Some Thoughts on L1CA/L2C Derived TEC
Paul Kintner, Aug. 2009 Cornell University
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Required Precision
- C/A and C code chip period 1ms
- A/D cadence is 175 ns (digitization rate)
- 1 TECU produces differential code arrival time of
about 0.54 ns or 16 cm at L1 (10 ns 20 TECU) - A/D samples at 175 ns so 0.5 ns is tough
- 1 TECU produce differential phase of 0.28 cycle
- Fraction of a cycle is easy to measure (IQ
clouds) - Examine Ithaca data from two consecutive days
using Bradys C receiver and data from digital
storage receiver - Night of April 18 and 19, 2009 PRN 7
- Use L1CA and L2CL with 1 ms accumulations, DLL
updated every 1 ms and PLL updated every 10 ms
and PR and phase reported every 20 ms
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Measurement Precision
0.02 cycle
TIME
PHASE
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Effect of zero mean white noise on ranging
Early
Late
TCd
T accumulation time d fraction of chip
time C/N0 carrier-to-noise ratio TC chip time
about 1 msec
TC
TC
For C/N0 44dB, TC 1 msec, BWDLL0.3 Hz, d
1, then sDP 0.73 m or 4.5 TECU
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Time of Arrival (TOA) TEC
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Comparison between Day1 and Day2 TOA TEC
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Comparison of Day1 and Day2 TOA TEC
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Difference Day 1 with Day 2
sDTEC sqrt(2).73m9.52 TECU/m 9.8 TECU
(theoretical value from noise, neglecting
multipath)
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Comparison of Day1 and Day2 Phase TEC
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Some Multipath in Phase TEC
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Difference Phase TEC Day1 with Day2Is this real?
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Recursive Filter
Current measurement of TEC by D(dt)
Difference in consecutive measurements of TEC by
D(df)
Previous estimate of TEC
Current estimate of TEC
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TOA TEC with Recursive Filter
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