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 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

I.M.Avruch

H.Bignall

A.Brunthaler R.M.Campbell M.A.Garrett L.I.Gurvits

S.V.Pogrebenko

ESA-ESTEC NASA-JPL

C.. van’t KloosterS.Asmar

J.-P.Lebreton

W.Folkner

R.A.Preston

ASTRON

A.R.Foley

U Bonn

M.Bird

ATNF

J.Lovell C.Phillips

J. Reynolds R.Sault.

T.Tzioumis

U Tasmania

G.Cimo S.Elingsen

B.Reid

NAO China

T.An (ShAO) X.Hong(ShAO) S.Huang(ShAO) D.Jiang(ShAO) X.Liu(UAO)

Helsinki University

A.Mujunen

J.Ritakari

NRAO

W.Brisken

F.Ghigo

G.Langston

J.Romney

NICT (CRL)

T.Kondo

ISAS

R.Dodson

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Spacecraft

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Signals

 Spacecraft Spectrum Coherent Harmonics Carrier

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Signals

 Tone Purity

I.Avruch, 8th EVN Symposium

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.

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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

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Signals (SMART-1 Impact on Moon)

http://sci.esa.int

Hobart 26m SMART-1 last light @ Hobart: 05:42:22.394060(5) 03 Sep 2006 UTC

I.Avruch, 8th EVN Symposium 28 Sep 2006

TIGO Concepcion 7

Signals (Huygens Probe)

 Huygens Probe Incident Power (1 IF of 16MHz Bandwidth)   AGN 50mJy Flux = 4x10 -21 W/m 2 Huygens Probe 3.7W in carrier line Flux = 5x10 -25 W/m 2  But Spectral Density is high.

 Dn ~ 20mHz g 2500Jy

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Signals

 Low occupation number for obs. Huygens carrier @ l 15cm 0.4 photons/ m 2 /s P/ hυ = 20 photons/s at VLBA_MK (500 at GBT)  Dn D t >= 1 g D t ~ 50s There are ~1000 photons in the system, on average.

The most sensitive VLBI Observation ever?

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VLBI and Spacecraft Navigation

 D DOR “Delta Differential One-way Ranging” i.e

. Group Delay Measurement.

CCSDS CP-5060WO-1.1

carrier S DOR tone & harmonics n f t=Df/Dn

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VLBI and Spacecraft Navigation



D DOR 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 ~ 0.15

ns

g

1.5mas

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VLBI on Spacecraft



Phase Delay

 Potential precision 1-10 ps g 15 m as (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

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VLBI on Spacecraft



Huygens Residual Phases



Delay model for near-field source.

Unfortunately, delay model is wrong!

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VLBI on Spacecraft

Huygens Trajectory on Titan

preliminary

09:11:10 SCET 

Note spread of the data points: ~ 1 km across the trajectory

11:08:11

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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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