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Range Bias vs Intensity 2005
Toshimichi Otsubo
Kashima Space Research CenterNational Institute of Information and Communications Technology
ILRS Fall 2005 Workshop, 5 Oct 2005
Satelllite signature
Transmitted pulse NOT equal to Return pulse– Multiple CCRs contributing to the return.– Where is the detection timing?
+
satellite
centre
(pulse transmittedfrom ground station)
(retroreflectedpulse)
cube corner reflectors
(imaginary pulse reflected
at centre)– Key error factor for TRF scale, GM, etc.
System-type-dependent centre-of-mass System-type-dependent centre-of-mass correctioncorrection
LAGEOSFrom Otsubo and Appleby, JGR, 2003.
0.25 0.24 (m)
251 “Standard”257.6r - nL
2453-sigma
242w/o clipping
245Ideal S.P. (<0.1 p.e.)
2491 p.e.
257100 p.e.
25610 p.e.
2561 ps
252100 ps
248300 ps
2441ns
2423ns FWHM
SingleSinglePhotonPhoton
C-SPADC-SPAD
PMTPMT(LEHM)(LEHM)
2502-sigma
2472.5-sigma
247249250252 (n=2.0)
245Hx
System-type-dependent centre-of-mass System-type-dependent centre-of-mass correctioncorrectionAJISAI
SingleSinglePhotonPhoton
C-SPADC-SPAD
1.00 0.95 (m)
1010 “Standard”1028r - nL
9763-sigma
962w/o clip
977Ideal S.P. (<0.1 p.e.)
9901 p.e.
1023100 p.e.
102010 p.e.
10221 ps
1017100 ps
1009300 ps
9931 ns
9763 ns FWHM
9852.5-sigma
9972-sigma
PMTPMT(LEHM)(LEHM)
977 (n=2.0)9879931002
985Hx
From Otsubo and Appleby, JGR, 2003.
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?
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”
Riga 1884: PMT
McDonald 7080: PMT
Yarragadee 7090: PMT
Greenbelt 7105: PMT
Monument Peak 7110: PMT
Changchun 7237: APD
Beijing 7249: APD
Hartebeestoek 7501: PMT
Zimmerwald 7810 (423 nm): APD
Zimmerwald 7810 (846 nm): APD
Borowiec 7811: PMT
San Fernando 7824: PMT
Mt Stromlo 7825: APD
Riyadh 7832: SPAD? (No SCI Log)
Grasse 7835: APD
Shanghai 7837: APD
Simosato 7838: PMT
Graz 7839: APD
Herstmonceux 7840: APD
Potsdam 7841: PMT
Matera 7941: PMT? (No SCI Log)
Wettzell 8834: PMT+APD (?)
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 +/- 10-15 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” !!
System-type-dependent centre-of-mass System-type-dependent centre-of-mass correctioncorrectionETALON
SingleSinglePhotonPhoton
C-SPADC-SPAD
0.60 0.55 (m)
576 “Standard”613r - nL
5563-sigma
552w/o clip
558 Ideal S.P. (<0.1 p.e.)
5731 p.e.
613100 p.e.
60810 p.e.
6121 ps
607100 ps
598300 ps
5781 ns
5623 ns FWHM
5802-sigma
5642.5-sigma
PMTPMT(LEHM)(LEHM)
570575582593 (n=2.0)
565Hx
From Otsubo and Appleby, JGR, 2003.