orbital frequencies of the two planets (here, 1 is the inner transiting planet and 2 is the outer one). The periods of these terms are comparable to the orbital periods and that’s why they are called the short-period TTVs. There is a slight complication as some identified frequencies can be aliases of $k_1 n_1 + k_2 n_2$. Still, given a set of frequencies, it should be possible to figure out which ones are real and which ones are aliases, eventually giving us $n_2$ (frequency $n_1$ is known from transits).

It then remains to match the observed amplitudes and phases to their theoretical expressions and we have a set of equations to compute unknowns, including masses of the two planets and their six orbital elements. That is, in general, 14 unknowns. Not all unknowns, however, can be determined from TTVs. For example, the unknown orbit orientation with respect to the sky plane causes a degeneracy in the nodal longitudes. The TTVs can be used to determine the difference, $\Omega_1-\Omega_2$, but not the individual values. Also, the true longitude of the transiting planet is known from the transit observations. So there are really only 12 unknowns. So, if the goal is to 