  We report high-precision X-ray monitoring observations in the 0.4-10 keV band
of the luminous, long-period colliding-wind binary Eta Carinae up to and
through its most recent X-ray minimum/periastron passage in February 2020. Eta
Carinae reached its observed maximum X-ray flux on 7 January 2020, at a flux
level of $3.30 \times 10^{-10}$ ergs s$^{-1}$ cm$^{-2}$, followed by a rapid
plunge to its observed minimum flux, $0.03 \times 10^{-10}$ ergs s$^{-1}$
cm$^{-2}$ near 17 February 2020. The NICER observations show an X-ray recovery
from minimum of only $\sim$16 days, the shortest X-ray minimum observed so far.
We provide new constraints of the "deep" and "shallow" minimum intervals.
Variations in the characteristic X-ray temperature of the hottest observed
X-ray emission indicate that the apex of the wind-wind "bow shock" enters the
companion's wind acceleration zone about 81 days before the start of the X-ray
minimum. There is a step-like increase in column density just before the X-ray
minimum, probably associated with the presence of dense clumps near the shock
apex. During recovery and after, the column density shows a smooth decline,
which agrees with previous $N_{H}$ measurements made by SWIFT at the same
orbital phase, indicating that changes in mass-loss rate are only a few percent
over the two cycles. Finally, we use the variations in the X-ray flux of the
outer ejecta seen by NICER to derive a kinetic X-ray luminosity of the ejecta
of $\sim 10^{41}$ ergs s$^{-1}$ near the time of the "Great Eruption'.
