  Here we present an analysis of the X-ray morphology and flux variability of
the particularly bright and extended Western hotspot in the nearest powerful
(FR II-type) radio galaxy, Pictor A, based on data obtained with the Chandra
X-ray Observatory. The hotspot marks the position where the relativistic jet,
that originates in the active nucleus of the system, interacts with the
intergalactic medium, at hundreds-of-kiloparsec distances from the host galaxy,
forming a termination shock that converts jet bulk kinetic energy to internal
energy of the plasma. The hotspot is bright in X-rays due to the synchrotron
emission of electrons accelerated to ultra-relativistic energies at the shock
front. In our analysis, we make use of several Chandra observations targeting
the hotspot over the last decades with various exposures and off-axis angles.
For each pointing, we study in detail the PSF, which allows us to perform the
image deconvolution, and to resolve the hotspot structure. In particular, the
brightest segment of the X-ray hotspot is observed to be extended in the
direction perpendicular to the jet, forming a thin, $\sim$3 kpc-long, feature
that we identify with the front of the reverse shock. The position of this
feature agrees well with the position of the optical intensity peak of the
hotspot, but is clearly off-set from the position of the radio intensity peak,
located $\sim$1 kpc further downstream. In addition, we measure the net count
rate on the deconvolved images, finding a gradual flux decrease by about 30%
over the 15-year timescale of the monitoring.
