  We present the result of a Chandra ACIS observation of the pulsar PSR
B1853+01 and its associated pulsar wind nebula (PWN), embedded within the
supernova remnant W44. A hard band ACIS map cleanly distinguishes the PWN from
the thermal emission of W44. The nebula is extended in the north-south
direction, with an extent about half that of the radio emission. Morphological
differences between the X-ray and radio images are apparent. Spectral fitting
reveals a clear difference in spectral index between the hard emission from PSR
B1853+01 (Gamma ~ 1.4) and the extended nebula (Gamma ~ 2.2). The more accurate
values for the X-ray flux and spectral index are used refine estimates for PWN
parameters, including magnetic field strength, the average Lorentz factor,
gamma, of the particles in the wind, the magnetization parameter, sigma, and
the ratio k of electrons to other particles.
