Recent Developments in Planetary Ephemeris...
Transcript of Recent Developments in Planetary Ephemeris...
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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
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range
resid
(m)
2004.0 2005.0 2006.0 2007.0 2008.0 2009.0 2010.0
-50
-25
0
25
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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)