1!

W. M. Folkner Jet Propulsion Laboratory

California Institute of Technology

Recent Developments in Planetary Ephemeris Observations

20 September 2010

This document has been reviewed for export control and does NOT contain controlled technical data.

©2010 California Institute of Technology. Government sponsorship acknowledged.

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•  Sensitivity to relativistic parameters in the ephemerides comes (mainly) through processed planetary spacecraft observations;

•  MESSENGER - Tony Taylor (Kinetx) •  Venus Express - Trevor Morley (ESOC) •  Mars ranging - Alex Konopliv (JPL); Trevor Morley (ESOC) •  Mars VLBI - Jim Border (JPL) •  Saturn r, α, δ - Bob Jacobson (JPL) •  Saturn VLBA Dayton Jones (JPL)/Ed Fomalont (NRAO) •  Astrometry - W. Owen (JPL), A. Monet, H. Harris (USNO)

Acknowledgements

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τ

CorrelatorBaseline B

θ

τ= B⋅cos(θ) /c

spacecraft d

elay τ

Ephemeris Tie to ICRF

•  VLBI measures spacecraft angular position relative to radio reference frame •  MGS, Odyssey, MRO

•  Doppler ties spacecraft position to center of planet •  Reconstructed accuracy <10m

•  VLBI measurement types; •  Doubly-difference range (ΔDOR)

•  DSN and ESA stations •  Differenced carrier phase

•  Very Long Baseline Array

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Mercury Orbit Data

-10.0

-5.00

0.00

5.00

10.0Arecibo Haystack Goldstone Eupatoria

resid

ual (

1-w

ay k

m)

1965 1975 19951985

-0.2

-0.1

0

0.10

0.2

resid

ual (

1-wa

y km

)

1974 19761975 -4

-2

0

2

4

right

asc

enci

on re

sid (m

as)

2008 2009 2010-4

-2

0

2

4

decl

inat

ion

resid

(mas

)

2008 2009 2010-100

-50

0

50

100

rang

e res

id (1

-way

m)

2008 2009 2010

Radar Ranging

Mariner 10 range MESSENGER Encounters

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Mercury Orbit Uncertainty w.r.t. Earth

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Venus Data

-10

-5

0

5

10

resid

ual (

mill

iarc

seco

nd)

1991 1994-10

-5

0

5

10

resid

ual (

mill

iarc

seco

nd)

1994.0 1994.75-8

-4

0

4

8

resid

ual (

mas

)

2007 2008 2009 2010

Venus Express Range

Magellan VLBI Venus Express VLBI

Goldstone-Canberra Goldstone-Madrid New Norcia - Cebreros

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Venus Orbit Uncertainty w.r.t. Earth

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Mars VLBI Data

-2

-1

0

1

2

resid

ual (

mas

)

2001.0 2003.0 2005.0 2007.0 2009.0

Mars Spacecraft VLBI on Goldstone-Madrid Baseline

2011.0

-2

-1

0

1

2

resid

ual (

mas

)

2001.0 2003.0 2005.0 2007.0 2009.0

Mars Spacecraft VLBI on Goldstone-Canberra Baseline

2011.0

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Mars Range Fit/Extrapolation

•  Mars spacecraft (MGS, ODY, MRO, MEX)range residuals show improving prediction •  DE 414 fit 67 asteroid GM

with constraints •  DE 418 and DE 421 fit to

11 asteroid GM with no constraint

•  DE423 fit to 21 asteroid GM with a priori uncertainty from Baer et al.

DE414

DE418

DE421

DE423

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Mars Orbit Uncertainty w.r.t. Earth

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Jupiter Astrometry Nikolaev Observatory USNO Flagstaff

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Jupiter Spacecraft Data

-40

-20

0

20

40

right

asc

ensio

n re

sid (m

as)

2000199019801970

Pioneer 10

Pioneer 11

Voyager 1

Voyager 2

Ulysses Cassini

-40

-20

0

20

40

decl

inat

ion

resid

(mas

)

2000199019801970

Pioneer 10

Pioneer 11

Voyager 1

Voyager 2 Ulysses Cassini

-4

-2

0

2

4

rang

e re

sid (k

m)

2000199019801970

Pioneer 10

Pioneer 11

Voyager 1

Voyager 2Ulysses

Cassini

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Jupiter Orbit Uncertainty w.r.t. Earth

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Cassini VLBA Observations

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Saturn Astrometry Nikolaev Observatory USNO Flagstaff

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Cassini Range to Saturn

•  Derived range to Saturn depends on spacecraft orbit estimate •  Range data usually used to estimate spacecraft maneuvers

•  May have unwanted correlations with range to Saturn

•  Doppler-only spacecraft orbits more independent, but noisier

-50

-25

0

25

50

range

resid

(m)

2004.0 2005.0 2006.0 2007.0 2008.0 2009.0 2010.0

-50

-25

0

25

50

range

resid

(m)

2004.0 2005.0 2006.0 2007.0 2008.0 2009.0 2010.0

Spacecraft orbits include ranging

Spacecraft orbits Doppler only

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Saturn Orbit Uncertainty w.r.t. Earth

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Uranus, Neptune, Pluto

•  Orbits dominated by astrometric observations •  Nikolaev, USNOFS, TMO •  Voyager 2 fly-bys of Uranus, Neptune, give 3-D point for one epoch

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Uranus Orbit Uncertainty w.r.t. Earth

Voyager 2 flyby

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Neptune Orbit Uncertainty w.r.t. Earth

Voyager 2 flyby

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Pluto Orbit Uncertainty w.r.t. Earth

New Horizons encounter

Desired Accuracy

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Future Plans

•  Deliver ephemerides for MSL cruise and arrival •  Improve Pluto for New Horizons encounter (2015)

•  Re-process old data? HST near radio source? GAIA/J-MAPS?

•  Long integration with converged LLR data •  Lunar core model without exponential damping •  Significant asteroids integrated along with planets

•  Mercury orbit from MESSENGER prime science phase (2011) •  Jupiter orbit from Juno (2016-2017)