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VLBI Observations of Spacecraft

VLBI Observations of Spacecraft. Ian Avruch * , JIVE. * On behalf of the Huygens VLBI Tracking 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

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VLBI Observations of Spacecraft

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  1. VLBI Observations of Spacecraft Ian Avruch*, JIVE *On behalf of the Huygens VLBI Tracking Team

  2. 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 Huygens: 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) I.Avruch, 8th EVN Symposium

  3. Spacecraft I.Avruch, 8th EVN Symposium

  4. Signals • Spacecraft Spectrum Carrier Coherent Harmonics I.Avruch, 8th EVN Symposium

  5. 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 LOvariance still present. I.Avruch, 8th EVN Symposium

  6. Signals (SMART-1 Occultation by Moon) SMART-1 carrier wave voltage, powerand phaseas detected by Medicina station Post-egress “classical” diffraction pattern and zoom on pre-egress features, like those seen around seconds 5 and 8-10 For comparison: power (red) and phase (blue) patterns for diffraction on a flat circular screen I.Avruch, 8th EVN Symposium

  7. Signals (SMART-1 Impact on Moon) http://sci.esa.int TIGO Concepcion Hobart 26m SMART-1 last light @ Hobart: 05:42:22.394060(5) 03 Sep 2006 UTC I.Avruch, 8th EVN Symposium

  8. 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 I.Avruch, 8th EVN Symposium

  9. 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? I.Avruch, 8th EVN Symposium

  10. VLBI and Spacecraft Navigation • DDOR “Delta Differential One-way Ranging” • i.e. Group Delay Measurement. DOR tone & harmonics CCSDS CP-5060WO-1.1 carrier S n t=Df/Dn f n I.Avruch, 8th EVN Symposium

  11. 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 I.Avruch, 8th EVN Symposium

  12. 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 I.Avruch, 8th EVN Symposium

  13. VLBI on Spacecraft • Huygens Residual Phases • Delay model for near-field source. Unfortunately, delay model is wrong! I.Avruch, 8th EVN Symposium

  14. 09:11:10 SCET 11:08:11 VLBI on Spacecraft Huygens Trajectory on Titan preliminary • Note spread of the data points: ~ 1 km across the trajectory I.Avruch, 8th EVN Symposium

  15. 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 I.Avruch, 8th EVN Symposium

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