... force

According to Nordtvedt (2003), the Earth-Moon range is affected by long-periodic harmonic perturbations of gravitomagnetic origin whose amplitudes are of the order of 5 m and the periods are monthly and semi-monthly. The amplitudes of the lunar motion at both these periods are determined to better than half a centimeter precision in the total orbital fit to the LLR data.

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... origin

In the case of the LAGEOS-LAGEOS II experiment in the gravitational field of the Earth, the non-gravitational effects also play a very important role, especially in perturbing the perigee of LAGEOS II. In the case of planetary motions the non-conservative forces are, instead, irrelevant.

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... harmonics

In general, they are the first low-degree ones J₂, J₄,...

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... evolution

Here we speak about nodal residuals in a, strictly speaking, improper sense. The Keplerian orbital elements are not directly observable: they can only be computed (in the case of the Solar System bodies exhibiting small inclinations the nodes should be obtained by the currently used parameters $\sin i\cos\Omega$ and $\sin i\sin\Omega$). The basic observable quantities are ranges, range-rates and angles. Here we mean the differences between the time series of the node computed from a given observed orbital arc and the time series of the node computed from a propagated orbital arc with the gravitomagnetic force switched off in the force models. The two time series share the same initial conditions. Note that the post-Newtonian equations of motion used at JPL for the computation of the planetary ephemerides (Estabrook 1971) do not include the gravitomagnetic force, so that the Lense-Thirring effect would automatically be absorbed in the time series of $\delta\Omega$.

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... especially

While the spacecraft trajectory will be determined from the range-rate data, the planet's orbit will be retrieved from the range data (Milani et al. 2002). In particular, the determination of the planetary centre of mass is important for this goal which can be better reached by a not too elliptical spacecraft orbit. The relatively moderate ellipticity of the planned $400\times 1500$ km polar orbit of BepiColombo, contrary to the much more elliptical path of Messenger, is, then, appropriate.

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... GTR

It can be shown that it can be expressed in terms of the PPNparameter $\gamma$.

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... inclination

As pointed out in Milani et al. (2002), the angle i refers to the inclination between the planet's orbital plane and the fixed reference plane of the celestial reference frame; it is not the angle $\epsilon$ between the planet's orbital plane and the ecliptic. It turns out that $i\sim\epsilon/2$. For Mercury $\epsilon=7.00487^\circ$.

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