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:
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
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.
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”
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” !!