  The neutron-rich mass region around $A\approx100$ presents challenges for
modeling the astrophysical $r$-process because of rapid shape transitions. We
report on mass measurements using the TITAN Penning trap at TRIUMF-ISAC to
attain more reliable theoretical predictions of $r$-process nucleosynthesis
paths in this region. A new approach using highly charged ($q=15+$) ions has
been applied which considerably saves measurement time and preserves accuracy.
New mass measurements of neutron-rich $^{94,97,98}$Rb and $^{94,97-99}$Sr have
uncertainties of less than 4 keV and show deviations of up to 11$\sigma$ to
previous measurements. An analysis using a parameterized $r$-process model is
performed and shows that mass uncertainties for the A=90 abundance region are
eliminated.
