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:
28 Sep 2006I.Avruch, 8th EVN Symposium 5
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.
28 Sep 2006I.Avruch, 8th EVN Symposium 6
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
28 Sep 2006I.Avruch, 8th EVN Symposium 7
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
28 Sep 2006I.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.
20mHz 2500Jy
28 Sep 2006I.Avruch, 8th EVN Symposium 9
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?
28 Sep 2006I.Avruch, 8th EVN Symposium 10
VLBI and Spacecraft Navigation
DOR “Delta Differential One-way Ranging” i.e. Group Delay Measurement.
CCSDS CP-5060WO-1.1
S
carrierDOR tone &harmonics
28 Sep 2006I.Avruch, 8th EVN Symposium 11
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
28 Sep 2006I.Avruch, 8th EVN Symposium 12
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
28 Sep 2006I.Avruch, 8th EVN Symposium 13
VLBI on Spacecraft
Huygens Residual Phases
Delay model for near-field source.
Unfortunately,delay model is wrong!
28 Sep 2006I.Avruch, 8th EVN Symposium 14
VLBI on Spacecraft
Note spread of the data points: ~ 1 km across the trajectory09:11:10 SCET
11:08:11
Huygens Trajectory on Titanpreliminary
28 Sep 2006I.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 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