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JPL radio science researchers participate in many NASA deep space missions. Their contribute to developing engineering requirements consistent with the scientific objectives for the spacecraft and ground elements of Radio Science instruments; participate in instrument design and development; acquire the science data; participate in analysis and interpretation.
Radio links between spacecraft and Earth are utilized to examine changes in the characteristics of the electromagnetic waves such as the phase/frequency, amplitude, radio spectrum, or polarization to investigate many aspects of planetary science, space physics and fundamental physics. Radio Science investigations include:
Currently, radio scientists at JPL are supporting several NASA missions, including Cassini, Mars Reconnaissance Orbiter, Dawn, and Messenger and preparing for upcoming missions that include GRAIL and Juno. They also support ESA missions Mars Express, Venus Express, and Rosetta. They have in the recent past conducted Radio Science experiments on Galileo, Mars Global Surveyor, Mars Odyssey, NEAR, Lunar Prospector, and other missions.
A profile of the rings of Saturn from radio occultations at three wavelengths (three radios on-board the Cassini spacecraft at different frequencies) S-band (red), X-band (green) and Ka-band (blue). The signal extinction is shown from which the optical thickness and particle size distribution are inferred The profile is superimposed on an image of the rings generated from radio occultation data (credit: E. A. Marouf, SJSU).
Recent Opportunities and Discoveries
A gravity map of Mars generated from radio tracking techniques shows variations esulting from surface and subsurface density variations (credit A.S. Konopliv, JPL).
Since 1995, RS has had a significant role in subsequent missions and is credited with the following additional accomplishments:
First detection of Martian core and bulk seasonal CO2 deposition at poles (Mars Pathfinder)
Vastly improved gravity field of Mars, with determination of Love number and correlation with topography (MGS, Odyssey, MRO, and Mars Express)
First detection of planetary gravity field variations other than Earth (MGS)
First determination of the mass of Phobos (MGS)
First non-spherical gravity field of an asteroid (NEAR mission to Eros)
High accuracy profiling of Martian atmospheric structure from radio occultations (MGS)
Detection of ionospheres on the Galilean Satellites (Galileo)
Jovian deep atmospheric wind speeds and ammonia concentration (Galileo Probe)
State-of-the art tests of General Relativity and search for gravitational waves (Cassini)
Improved gravity field of Mercury (MESSENGER)
Measurement of Mars upper atmospheric density from spacecraft drag (several orbiters)
Surface characteristics of Venus, Moon, Mars and Titan from bistatic radar experiments
Detection of meteor layers in ionospheres of Mars and Venus (Mars Express, Venus Express)
Modeling the mass distribution in the interiors of the large moons of Jupiter (Galileo)
Height profile of winds on Titan with the Doppler Wind Experiment (Huygens)
High resolution gravitational field of the Earth via spacecraft-to-spacecraft links (GRACE)
Gravitational field of Saturn and its large satellites (Cassini)
Atmospheric Structure of Saturn and its large satellites (Cassini)
Profiling of internal dynamics and of particle size distribution within Saturn’s rings (Cassini)
First direct gravity measurements in the lunar farside (SELENE (Kaguya)).
Future missions could potentially include significant RS investigations such as:
Dawn: Coherent X-band Doppler tracking could enable the measurement of the gravity field of Vesta and Ceres and constrain their interior structure.
Rosetta: RS objectives include measurements of cometary nucleus mass, bulk density, and internal structure as well the composition and roughness of the nucleus surface.
Juno: Coherent X- and Ka-band links would enable precise measurement of spacecraft motion during close polar orbits to determine the gravity field, distribution of mass, core characteristics, and convective motion in the deep atmosphere.
GRAIL: Spacecraft-to-spacecraft radio links at Ka-band, timing synchronization at S-band, and X-band Doppler links to Earth would enable the Gravity Recovery and Interior Laboratory to measure the lunar gravity field in unprecedented detail to be used to probe the Moon’s interior from crust to core, reveal its subsurface structure, reconstruct its thermal history, and place limits on a possible inner core.
New Horizons: High-precision uplink radio occultation would allow derivation of Pluto's atmospheric structure while Doppler tracking will constrain interior structure.
ExoMars: Links from a possible future Mars lander/rover or network would potentially improve knowledge of the interior structure by determining the total moment of inertia, core moment of inertia and state of the core in order to constrain the evolution of the planet Mars.
BepiColombo: Order-of-magnitude improved Ka-Band Doppler and ranging would enable: (1) investigating the interior structure of Mercury, (2) testing relativistic gravity and significantly improved General Relativity post-Newtonian parameters, (3) testing any time variation of the gravitation constant to high accuracy, (4) determining the solar oblateness to high accuracy (5) characterizing the structure of the solar wind in and out of the solar ecliptic.