  Earth-based Very Long Baseline Interferometry (VLBI) has made rapid advances
in imaging black holes. However, due to the limitations imposed on terrestrial
VLBI by the Earth's finite size and turbulent atmosphere, it is imperative to
have a space-based component in future VLBI missions. Herein, this paper
investigates the effect of Earth's oblateness, also known as the $J_{2}$
effect, on orbiters in Earth-Space and Space-Space VLBI. The paper provides an
extensive discussion on how the $J_{2}$ effect can directly impact orbit
selection for black hole observations and how through informed choices of
orbital parameters, the effect can be used to the mission's advantage, a fact
that has not been addressed in existing space-VLBI investigations. We provide a
comprehensive study of how the orbital parameters of several current space VLBI
proposals will vary specifically due to the $J_{2}$ effect. For black hole
accretion flow targets of interest, we have demonstrated how the $J_{2}$ effect
leads to modest increase in shorter baseline coverage, filling gaps in the
$(u,v)$ plane. Subsequently, we construct a simple analytical formalism that
allows isolation of the impact of the $J_{2}$ effect on the $(u,v)$ plane
without requiring computationally intensive orbit propagation simulations. By
directly constructing $(u,v)$ coverage using the $J_{2}$ affected and invariant
equations of motion, we obtain distinct coverage patterns for M87* and SgrA*
that show extremely dense coverage on short baselines as well as long term
orbital stability on longer baselines.
