Modeling Jupiter's Local Gravitational Field Using Ring Mascons
Abstract
The global gravitational field of a celestial body is classically represented by means of an expansion in series of spherical harmonics. The coefficients of the expansion, called spherical harmonic coefficients, hold all the information regarding the mass distribution of the body. In the case of rocky bodies like the Earth's Moon, significant local mass anomalies, often associated with the presence of large craters, are modeled using mascons. These are pointwise mass concentrations added to the spherical harmonic expansion of the body's gravity field, with the aim to account for the local observed mass variation.
In the case of fluid bodies the concept of mascon can be generalized in order to take into account the nature of the planet, by introducing ring mascons, mass concentrations in shape of a ring, which model near-axially-symmetric mass anomalies. Through numerical simulations and possibly real data analysis, in this work we explore the possibility of using ring mascons for the determination of the gravity field of Jupiter with Juno. The orbital geometry causes the spacecraft to fly by the planet at a very low altitude (~4000 km) during the six-hour perijove pass and stay very far for the rest of the 53-day polar orbit. The latitude of the pericenter is not fixed: with every orbit it increases by about 1 degree as an effect of Jupiter's oblateness. The portion of the planet corresponding to the latitudes of the pericenters is the one where the gravity field is observed with the highest resolution. Therefore, instead of determining a global gravity field using a high-degree (l=25 or l=30) spherical harmonic expansion, we reconstruct the local gravity field of the region of latitudes covered by the spacecraft. The considered model for Jupiter's gravitational potential is the combination of a degree-10 zonal spherical harmonic expansion and the potential of a number of ring mascons located in the latitude band corresponding to Juno's pericenters latitudes. The zonal coefficients as well as the masses of the rings are adjusted in a least square fit. The uncertainties of the parameters are mapped to gravity anomalies uncertainties and compared to those obtained considering a global gravity field.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.P21H3465S
- Keywords:
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- 5714 Gravitational fields;
- PLANETARY SCIENCES: FLUID PLANETS;
- 5734 Magnetic fields and magnetism;
- PLANETARY SCIENCES: FLUID PLANETS;
- 6220 Jupiter;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS;
- 6275 Saturn;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS