VLBI Observations of Spacecraft Ian Avruch*, JIVE *On behalf of the Huygens VLBI Tracking Team This tutorial is divided in two parts connected by the methodology – VLBI.

I.Avruch, 8th EVN Symposium 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 28 Sep 2006

I.Avruch, 8th EVN Symposium Spacecraft I.Avruch, 8th EVN Symposium 28 Sep 2006

I.Avruch, 8th EVN Symposium Signals Spacecraft Spectrum Coherent Harmonics Carrier I.Avruch, 8th EVN Symposium 28 Sep 2006

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. I.Avruch, 8th EVN Symposium 28 Sep 2006

Signals (SMART-1 Occultation by Moon) SMART-1 carrier wave voltage, power and phase as 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 28 Sep 2006

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 28 Sep 2006

Signals (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 28 Sep 2006

I.Avruch, 8th EVN Symposium 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 28 Sep 2006

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 28 Sep 2006

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 28 Sep 2006

I.Avruch, 8th EVN Symposium 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 28 Sep 2006

I.Avruch, 8th EVN Symposium VLBI on Spacecraft Huygens Residual Phases Delay model for near-field source. Unfortunately, delay model is wrong! I.Avruch, 8th EVN Symposium 28 Sep 2006

VLBI on Spacecraft Huygens Trajectory on Titan preliminary 11:08:11 Note spread of the data points: ~ 1 km across the trajectory 09:11:10 SCET 11:08:11 I.Avruch, 8th EVN Symposium 28 Sep 2006

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 28 Sep 2006