Ian Avruch

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Information about Ian Avruch
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Published on January 16, 2008

Author: Stefanie

Source: authorstream.com

Slide1:  Ian Avruch*, JIVE *On behalf of the Huygens VLBI Tracking Team Team:  Team SMART-1: S. Pogrebenko, JIVE, NL I. Avruch, JIVE, NL R. Campbell, JIVE, NL L. Gurvits, JIVE, NL R. Oerlemans, JIVE, NL A. Szomoru, JIVE,NL A. Mujunen, HUT/MRO, FI J. Ritakari, HUT/MRO, FI J. Wagner, HUT/MRO, FI G. Maccaferri, INAF/IRA, IT S. Montebugnoli, INAF/IRA, IT A. Foley, ASTRON/WSRT, NL O. Camino, ESA/ESOC, DE B. Foing, ESA/ESTEC, NL K. van’t Klooster, ESA/ESTEC, NL T. Morley, ESA/ESOC, DE L. Petrov, NASA/GSFC, USA With special thanks to Klaas Stuurwold, ASTRON,NL JIVE ESA-ESTEC NASA-JPL NRAO I.M.Avruch C.. van’t Klooster S.Asmar W.Brisken H.Bignall J.-P.Lebreton W.Folkner F.Ghigo A.Brunthaler R.A.Preston G.Langston R.M.Campbell J.Romney M.A.Garrett L.I.Gurvits S.V.Pogrebenko ASTRON ATNF U Tasmania NICT (CRL) A.R.Foley J.Lovell G.Cimo T.Kondo C.Phillips S.Elingsen U Bonn J. Reynolds B.Reid M.Bird R.Sault. T.Tzioumis NAO China Helsinki University ISAS T.An (ShAO) A.Mujunen R.Dodson X.Hong(ShAO) J.Ritakari S.Huang(ShAO) D.Jiang(ShAO) X.Liu(UAO) Huygens: Spacecraft:  Spacecraft Signals:  Signals Spacecraft Spectrum Carrier Coherent Harmonics Signals:  Signals Tone Purity Dynamic Spectrum of Smart1 TX carrier line detected by Medicina telescope at 2.235 GHz ( Frequency resolution 24 Hz) After tracking smooth frequency deviations, Frequency residual < 1 mHz Velocity residual < 0.1 mm/s Of course, this is just instrumental accuracy; short-term propagation effects and S/C LO variance still present. Signals (SMART-1 Occultation by Moon):  Signals (SMART-1 Occultation by Moon) SMART-1 carrier wave voltage, power and phase as detected by Medicina station For comparison: power (red) and phase (blue) patterns for diffraction on a flat circular screen Post-egress “classical” diffraction pattern and zoom on pre-egress features, like those seen around seconds 5 and 8-10 Signals (SMART-1 Impact on Moon):  Signals (SMART-1 Impact on Moon) http://sci.esa.int Hobart 26m TIGO Concepcion SMART-1 last light @ Hobart: 05:42:22.394060(5) 03 Sep 2006 UTC Signals (Huygens Probe):  Signals (Huygens Probe) Huygens Probe Incident Power (1 IF of 16MHz Bandwidth) AGN 50mJy Flux = 4x10-21 W/m2 Huygens Probe 3.7W in carrier line Flux = 5x10-25 W/m2 But Spectral Density is high. Dn ~ 20mHz g2500Jy Signals:  Signals Low occupation number for obs. Huygens carrier @ l 15cm 0.4 photons/m2/s P/hυ = 20 photons/s at VLBA_MK (500 at GBT) Dn Dt >= 1 gDt ~ 50s There are ~1000 photons in the system, on average. The most sensitive VLBI Observation ever? VLBI and Spacecraft Navigation:  VLBI and Spacecraft Navigation DDOR “Delta Differential One-way Ranging” i.e. Group Delay Measurement. CCSDS CP-5060WO-1.1 S n f n t=Df/Dn carrier DOR tone & harmonics VLBI and Spacecraft Navigation:  VLBI and Spacecraft Navigation DDOR Technique: The s.c. carrier (S,X, or Ka band) is modulated, producing a number of harmonics. 1 hour is spent on a QSO-s.c. scan cycle, 5-10min per source. S.c. with narrow channels (50kHz) centered on tones, QSO with wide channels (2MHz) centered same. Group Delay measured for both, differenced, gives s.c. position relative to QSO. Precision: dt ~ 0.15ns g 1.5mas VLBI on Spacecraft:  VLBI on Spacecraft Phase Delay Potential precision 1-10 ps g 15mas (at the limit of delay model precision) SMART-1 Correlation Without Delay Modeling Short term phase noise 65 milliradian (or 4.6 ps) rms at 40 ms sampling, Initial phase ambiguity ~ several cycles VLBI on Spacecraft:  VLBI on Spacecraft Huygens Residual Phases Delay model for near-field source. Unfortunately, delay model is wrong! VLBI on Spacecraft:  VLBI on Spacecraft Note spread of the data points: ~ 1 km across the trajectory Huygens Trajectory on Titan preliminary Current & Future Developments:  Current & Future Developments Self-consistent VLBI Delay Model for near-zone objects “VTD” VLBI package by L.Petrov(NASA GSFC) ps precision for Earth-bound observers SPICE package for spacecraft navigation Newtonian g ms precision anywhere in the SS Time is right for a convergence VLBI observations from space Applications for precise path-lengths Plate tectonics on Europa Dynamic gravitational lensing GR Tests: Pioneer Anomaly

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