Deriving Mercury geodetic parameters with altimetric crossovers from the
Mercury Laser Altimeter (MLA)
Based on previous applications of laser altimetry to planetary geodesy
at GSFC, we use the recently developed PyXover software package to
analyze altimetric crossovers from the Mercury Laser Altimeter (MLA).
Using PyXover, we place new constraints on Mercury’s geodetic parameters
via least‐squares minimization of crossover discrepancies. We
simultaneously solve for orbital corrections for each MLA ground track,
for the geodetic parameters of the IAU‐recommended orientation model for
Mercury (pole right‐ascension and declination coordinates, prime
meridian rotation rate and librations), and for the Mercury’s Love
number h2. We calibrate the formal errors of our solution based on
closed‐loop simulations and on the level of robustness against a priori
values, data selection, and parametrization. Our solution of the
Mercury’s rotational parameters is consistent with published values. In
particular, our new estimate for the orientation of the pole places
Mercury in a Cassini state, with an obliquity ϵ = 2.031 ± 0.03 arcmin
compatible with previous “surface” related measurements. Moreover, we
provide a first data‐based estimate of the Love number h2 = 1.55 ± 0.65.
The latter is consistent with expectations from models of Mercury’s
interior, although its precision does not enable their refinement.