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Range Bias vs Intensity 2005 Toshimichi Otsubo Kashima Space Research Center National Institute of Information and Communications Technology ILRS Fall.

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Presentation on theme: "Range Bias vs Intensity 2005 Toshimichi Otsubo Kashima Space Research Center National Institute of Information and Communications Technology ILRS Fall."— Presentation transcript:

1 Range Bias vs Intensity 2005 Toshimichi Otsubo Kashima Space Research Center National Institute of Information and Communications Technology ILRS Fall 2005 Workshop, 5 Oct 2005

2 Satelllite signature Transmitted pulse NOT equal to Return pulse –Multiple CCRs contributing to the return. –Where is the detection timing? –Key error factor for TRF scale, GM, etc.

3 System-type-dependent centre-of-mass correction LAGEOS From Otsubo and Appleby, JGR, (m) 251 “Standard”257.6 r - nL sigma 242 w/o clipping 245 Ideal S.P. (<0.1 p.e.) p.e p.e p.e ps ps ps 244 1ns 242 3ns FWHM SinglePhoton C-SPAD PMT(LEHM) sigma sigma (n=2.0) 245 Hx

4 System-type-dependent centre-of-mass correction AJISAI SinglePhoton C-SPAD (m) 1010 “Standard” 1028 r - nL sigma 962 w/o clip 977 Ideal S.P. (<0.1 p.e.) p.e p.e p.e ps ps ps ns ns FWHM sigma sigma PMT(LEHM) 977(n=2.0) Hx From Otsubo and Appleby, JGR, 2003.

5 Intensity-dependent Bias Are CoM corrections constant in the real world? –Big challenge for “mm accuracy” Systematic error  harmful in the analysis stage –Likely to be elevation-angle-dependent –Directly contaminates station heights (Otsubo, 2004). –Short pulse: fully compensated by C-SPAD / CFD. –Long pulse: target signature (STRL < LAG < AJI) –The stronger, the shorter? Not so simple?

6 Bias vs Intensity: Analysis Procedure Use of “Returns per NP bin” as intensity parameter –Strong signal  High return rate –Weak signal  Low return rate (Extreme: single photon) Orbit determination –Period: Jan 2004 to Jul 2005 (210 days) –Satellites: LAG1+LAG2, AJISAI, STARLETTE+STELLA –‘ concerto v4 ’ solved for orbits, station position & range bias –Stations: Top 20 in Quarterly Performance Card (Thanks Mark!) –Post-fit residuals sorted by “returns per NP bin”

7 Riga 1884: PMT

8 McDonald 7080: PMT

9 Yarragadee 7090: PMT

10 Greenbelt 7105: PMT

11 Monument Peak 7110: PMT

12 Changchun 7237: APD

13 Beijing 7249: APD

14 Hartebeestoek 7501: PMT

15 Zimmerwald 7810 (423 nm): APD

16 Zimmerwald 7810 (846 nm): APD

17 Borowiec 7811: PMT

18 San Fernando 7824: PMT

19 Mt Stromlo 7825: APD

20 Riyadh 7832: SPAD? (No SCI Log)

21 Grasse 7835: APD

22 Shanghai 7837: APD

23 Simosato 7838: PMT

24 Graz 7839: APD

25 Herstmonceux 7840: APD

26 Potsdam 7841: PMT

27 Matera 7941: PMT? (No SCI Log)

28 Wettzell 8834: PMT+APD (?)

29 Discussions: 1 mm accuracy? Still things to do! “Bias vs Intensity”: overall summary –Up to +/- 5 mm for LAG1+LAG2 and STRL+STEL. –Up to +/ mm for AJI. –Single photon systems behave superbly. –The result is most likely to be underestimated. –It has already affected TRFs for a long time. Necessity to eliminate the intensity dependence –Accurate vertical component is our strength! –Think “accuracy” instead of “single shot rms” or “# of returns.” –Let us see “High-Low Experiments” !!

30

31 System-type-dependent centre-of-mass correction ETALON SinglePhoton C-SPAD (m) 576 “Standard”613 r - nL sigma 552 w/o clip 558 Ideal S.P. (<0.1 p.e.) p.e p.e p.e ps ps ps ns ns FWHM sigma sigma PMT(LEHM) (n=2.0) 565 Hx From Otsubo and Appleby, JGR, 2003.


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