Huygens the Planetary Probe

under VLBI Magnifier

Leonid GurvitsJoint Institute for VLBI in Europe (JIVE)Dwingeloo, The Netherlands

1629-1695 1625-1712

15.10.1997

Huygens entry, descent and landing: 14 Jan 2005

7 July 2005L.Gurvits, EC Press Conference, Dwingeloo, NL 4

Radio astronomy segment of the Huygens mission

Conceived as an Earth-based support to the Doppler Wind Experiment (DWE)

Included Direct carrier signal detection with DSN-supplied Radio Sci Receiver

(real time capability) at Green Bank and Parkes telescopes; Direct Doppler measurements (JPL-led experiment) at four NRAO

VLBA antennas; Very Long Baseline Interferometry (VLBI) tracking of the probe from

17 radio telescopes (including all six above);

Used (only!) the Channel A carrier signal at 2040 MHz only.

7 July 2005L.Gurvits, EC Press Conference, Dwingeloo, NL 5

Interferometry: a one-slide tutorial

Michelson & Young, 1890s: measurements of stars’ diametres

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Very Long Baseline Interferometry (VLBI):

the ultimate angular resolution in astrophysics

VLBI tracking of Huygens, 14 January 2005

09:30 UTC 16:00 UTC

Huygens VLBI tracking obtained:• 340 min of carrier signal• 26 TByte of data (equivalent of ~6,000 DVD movies)

Huygens signal paths

Cassini S/C

TCXO TCXO

TCXORUSO

TCXORUSO

Channel B

Channel A

“Channel C” – eavesdropping on Channel A carrier

Huygens Data

HuygensReceivers

HuygensProbe

7 July 2005L.Gurvits, EC Press Conference, Dwingeloo, NL 8

Huygens radial velocity measurements

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VLBI determination of the Huygens descent trajectory

“Doppler interferometry”: ~25 km

A priori accuracy: ~100 km

Full VLBI accuracy: ~ 1 km

VLBI tracking of the Huygens Probe

• Pushing the limits of high technology

• Demonstrates high-level synergy between radio astronomy and space exploration

• Paves the way for future experiments and applications – GPS-like accuracy anywhere in Solar System (Moon, inner and outer planets)

• Great promise of next generation radio telescopes and arrays (e.g. Square Kilometre Array, SKA)

7 July 2005L.Gurvits, EC Press Conference, Dwingeloo, NL 11

Huygens VLBI tracking team (abbreviated)

JIVE ESA-ESTEC NASA-JPL NRAOI.M.Avruch C.. van’t Klooster S.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.Gurvits, R.OerlemansS.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.ReidM.Bird R.Sault.

T.Tzioumis

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

12 institutes and international 12 institutes and international organisations in 7 countriesorganisations in 7 countries