  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.
