Recent Developments in Planetary Ephemeris Observations W. M. Folkner 2 September 21 21. Government sponsorship acknowledged. 1!
Acknowledgements 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) 2!
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 <1m VLBI measurement types; Doubly-difference range (ΔDOR) DSN and ESA stations Differenced carrier phase Very Long Baseline Array spacecraft delay τ θ Baseline B τ = B cos(θ)/c Correlator τ 3!
Mercury Orbit Data 1. Radar Ranging Arecibo Haystack Goldstone Eupatoria residual (1-way km) 5.. -5. -1. 1965 1975 1985 1995 Mariner 1 range MESSENGER Encounters residual (1-way km).2.1 -.1 -.2 1974 1975 1976-4 right ascencion resid (mas) 4 2-2 28 29 21 declination resid (mas) 4 2-2 -4 28 29 21 range resid (1-way m) 1 5-5 -1 28 29 21 4!
Mercury Orbit Uncertainty w.r.t. Earth 5!
Venus Data Venus Express Range Magellan VLBI Venus Express VLBI residual (milliarcsecond) 1 5-5 -1 Goldstone-Canberra 1991 1994 5-5 -1 1994. 1994.75 residual (milliarcsecond)1 Goldstone-Madrid residual (mas) 8 New Norcia - Cebreros 4-4 -8 27 28 29 21 6!
Venus Orbit Uncertainty w.r.t. Earth 7!
Mars VLBI Data 2 Mars Spacecraft VLBI on Goldstone-Madrid Baseline 1 residual (mas) -1-2 21. 23. 25. 27. 29. 211. 2 Mars Spacecraft VLBI on Goldstone-Canberra Baseline 1 residual (mas) -1-2 21. 23. 25. 27. 29. 211. 8!
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 9!
Mars Orbit Uncertainty w.r.t. Earth 1!
Jupiter Astrometry Nikolaev Observatory USNO Flagstaff 11!
Jupiter Spacecraft Data right ascension resid (mas) 4 Pioneer 1 2-2 -4 197 Voyager 1 Voyager 2 Pioneer 11 198 Ulysses 199 Cassini 2 declination resid (mas) 4 Pioneer 1 2-2 -4 197 Voyager 1 Voyager 2 Ulysses Cassini Pioneer 11 198 199 2 4 range resid (km) 2-2 -4 Pioneer 1 Voyager 1 Pioneer 11 Voyager 2 Ulysses Cassini 197 198 199 2 12!
Jupiter Orbit Uncertainty w.r.t. Earth 13!
Cassini VLBA Observations 14!
Saturn Astrometry Nikolaev Observatory USNO Flagstaff 15!
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 5 range resid (m) 25-25 Spacecraft orbits include ranging -5 24. 25. 26. 27. 28. 29. 21. 5 range resid (m) 25-25 Spacecraft orbits Doppler only -5 24. 25. 26. 27. 28. 29. 21. 16!
Saturn Orbit Uncertainty w.r.t. Earth 17!
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 18!
Uranus Orbit Uncertainty w.r.t. Earth Voyager 2 flyby 19!
Neptune Orbit Uncertainty w.r.t. Earth Voyager 2 flyby 2!
Pluto Orbit Uncertainty w.r.t. Earth New Horizons encounter Desired Accuracy 21!
Future Plans Deliver ephemerides for MSL cruise and arrival Improve Pluto for New Horizons encounter (215) 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 (211) Jupiter orbit from Juno (216-217) 22!