On the use of different function bases for the determination of Jupiter's gravity field
Abstract
The Juno mission is approaching the landmark of 30 close encounters with Jupiter, designed for the study of the magnetosphere, atmosphere and gravity field of the planet. While orbiting the gas giant in a quasi-polar eccentric trajectory, the spacecraft maintains almost constant communication with Earth's ground stations through its HGA. Radio links are used for precise Doppler-tracking of the probe, which are exploited both for navigation purposes and for the determination of Jupiter's gravity field. The latter is connected to the deep structure of the planet and its strong atmospheric dynamics. The low-degree gravity field constitutes the strongest deviation from spherical symmetry and perturbs the trajectory of the spacecraft throughout the duration of the perijove (closest approach to Jupiter), about 2 hours around periapsis from north to south pole. On the other hand, since the term of degree l of Jupiter's gravitational potential is proportional to the inverse of the lth power of the distance between the spacecraft and the planet, the Juno spacecraft is sensitive to short-scale or high-degree variations of the gravity field of Jupiter only when extremely close to the planet (<1.1 Jupiter's radii). Juno perijove latitudes are concentrated between 4 and 29 degrees north during the span of the nominal mission. Here we explore the use of a combination of function bases, namely spherical harmonics and Slepian functions, for the optimal determination of the low-degree and high-degree gravity field of Jupiter. The latter basis is tailored for the Juno trajectory, and the estimated values of the Slepian coefficients from the Juno data match the predicted thermal wind values for a specific wind depth. The approach allows the concurrent estimation of the global and local gravity field of Jupiter, which is desired for the study of both the deep interior of the planet and the surface atmospheric dynamics.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMP090...03P
- Keywords:
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- 5714 Gravitational fields;
- PLANETARY SCIENCES: FLUID PLANETS;
- 5724 Interiors;
- PLANETARY SCIENCES: FLUID PLANETS;
- 6220 Jupiter;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS;
- 6275 Saturn;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS