  Massive black hole binaries are key targets for the space based gravitational
wave interferometer LISA. Several studies have investigated how LISA
observations could be used to constrain the parameters of these systems. Until
recently, most of these studies have ignored the higher harmonic corrections to
the waveforms. Here we analyze the effects of the higher harmonics in more
detail by performing extensive Monte Carlo simulations. We pay particular
attention to how the higher harmonics impact parameter correlations, and show
that the additional harmonics help mitigate the impact of having two laser
links fail, by allowing for an instantaneous measurement of the gravitational
wave polarization with a single interferometer channel. By looking at parameter
correlations we are able to explain why certain mass ratios provide dramatic
improvements in certain parameter estimations, and illustrate how the improved
polarization measurement improves the prospects for single interferometer
operation.
