Expected Precision of Europa Clipper Gravity Measurements

TL;DR

This paper simulates Europa Clipper's gravity measurements to assess the potential for detecting a subsurface ocean and characterizing Europa's interior, emphasizing the importance of DSN tracking assets and measurement precision.

Contribution

It provides detailed covariance analyses of gravity measurement precision using simulated data, including radar altimeter crossover ranges, for Europa Clipper's mission.

Findings

Some DSN configurations can confirm the presence of a global ocean.

Measurement precision allows estimation of Europa's gravity coefficients and tidal Love number.

Adequate crossover range performance can assess ice shell hydrostaticity.

Abstract

The primary gravity science objective of NASA's Clipper mission to Europa is to confirm the presence or absence of a global subsurface ocean beneath Europa's Icy crust. Gravity field measurements obtained with a radio science investigation can reveal much about Europa's interior structure. Here, we conduct extensive simulations of the radio science measurements with the anticipated spacecraft trajectory and attitude (17F12v2) and assets on the spacecraft and the ground, including antenna orientations and beam patterns, transmitter characteristics, and receiver noise figures. In addition to two-way Doppler measurements, we also include radar altimeter crossover range measurements. We concentrate on +/-2 hour intervals centered on the closest approach of each of the 46 flybys. Our covariance analyses reveal the precision with which the tidal Love number k2, second-degree gravity coefficients C20 and C22, and higher-order gravity coefficients can be determined. The results depend on the Deep Space Network (DSN) assets that are deployed to track the spacecraft. We find that some DSN allocations are sufficient to conclusively confirm the presence or absence of a global ocean. Given adequate crossover range performance, it is also possible to evaluate whether the ice shell is hydrostatic.