Ian Avruch, JIVE On behalf of the Huygens VLBI Tracking Team.

Ian AvruchIan Avruch**, , JIVEJIVE

**On behalf of the Huygens On behalf of the Huygens VLBI Tracking TeamVLBI Tracking Team

28 Sep 2006I.Avruch, 8th EVN Symposium 2

Team SMART-1:S. Pogrebenko, JIVE, NLI. Avruch, JIVE, NLR. Campbell, JIVE, NLL. Gurvits, JIVE, NLR. Oerlemans, JIVE, NLA. Szomoru, JIVE,NLA. Mujunen, HUT/MRO, FIJ. Ritakari, HUT/MRO, FIJ. Wagner, HUT/MRO, FIG. Maccaferri, INAF/IRA, ITS. Montebugnoli, INAF/IRA, ITA. Foley, ASTRON/WSRT, NLO. Camino, ESA/ESOC, DEB. Foing, ESA/ESTEC, NLK. van’t Klooster, ESA/ESTEC, NLT. Morley, ESA/ESOC, DEL. Petrov, NASA/GSFC, USA With special thanks to Klaas Stuurwold, ASTRON,NL

JIVE ESA-ESTEC NASA-JPL NRAOI.M.Avruch C.. van’t KloosterS.Asmar W.BriskenH.Bignall J.-P.Lebreton W.Folkner F.GhigoA.Brunthaler R.A.Preston G.LangstonR.M.Campbell J.RomneyM.A.Garrett L.I.GurvitsS.V.Pogrebenko

ASTRON ATNF U Tasmania NICT (CRL)A.R.Foley J.Lovell G.Cimo T.Kondo

C.Phillips S.ElingsenU Bonn J. Reynolds B.ReidM.Bird R.Sault.

T.Tzioumis

NAO China Helsinki University ISAST.An (ShAO) A.Mujunen R.DodsonX.Hong(ShAO) J.RitakariS.Huang(ShAO)D.Jiang(ShAO)X.Liu(UAO)

Huygens:


Spacecraft


Signals

Spacecraft Spectrum

CarrierCoherent Harmonics


Signals

Tone Purity

Dynamic Spectrum ofSmart1 TX carrier line

detectedby Medicina telescope at

2.235 GHz( Frequency resolution 24 Hz)

After tracking smooth frequency deviations,

Frequency residual < 1 mHzVelocity 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)

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)

http://sci.esa.int

Hobart 26m TIGO Concepcion

SMART-1 lastlight @ Hobart:05:42:22.394060(5)03 Sep 2006 UTC


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.

20mHz 2500Jy


Signals

Low occupation number for obs. Huygens carrier@ 15cm 0.4 photons/m2/s

P/hυ = 20 photons/s at VLBA_MK (500 at GBT)

t t50s

There are ~1000 photons in the system, on average.

The most sensitive VLBIObservation ever?


VLBI and Spacecraft Navigation

DOR “Delta Differential One-way Ranging” i.e. Group Delay Measurement.

CCSDS CP-5060WO-1.1

S

carrierDOR tone &harmonics


VLBI and Spacecraft Navigation

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: ns 1.5mas


VLBI on Spacecraft

Phase Delay Potential precision 1-10 ps 15as

(at the limit of delay model precision)

SMART-1 CorrelationWithout Delay Modeling

Short term phase noise65 milliradian (or 4.6 ps)rms at 40 ms sampling,

Initial phase ambiguity~ several cycles


VLBI on Spacecraft

Huygens Residual Phases

Delay model for near-field source.

Unfortunately,delay model is wrong!


VLBI on Spacecraft

Note spread of the data points: ~ 1 km across the trajectory09:11:10 SCET

11:08:11

Huygens Trajectory on Titanpreliminary


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 ms precision anywhere in the SSTime is right for a convergenceVLBI observations from space

Applications for precise path-lengths Plate tectonics on Europa Dynamic gravitational lensing GR Tests: Pioneer Anomaly

Ian Avruch, JIVE On behalf of the Huygens VLBI Tracking Team.

Documents

Transcript of Ian Avruch, JIVE On behalf of the Huygens VLBI Tracking Team.

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

Documents

Transcript of Ian Avruch*, JIVE *On behalf of the Huygens VLBI Tracking Team.

Ian Avruch, JIVE On behalf of the Huygens VLBI Tracking Team.

Transcript of Ian Avruch, JIVE On behalf of the Huygens VLBI Tracking Team.