  We report on X-ray observations of the the large-scale jets recently
discovered in the radio and detected in X-rays from the black hole candidate
X-ray transient and microquasar XTE J1550-564. On 11 March 2002, X-ray emission
was detected 23 arcsec to the West of the black hole candidate and was extended
along the jet axis with a full width at half maximum of 1.2 arcsec and a full
width at 10% of maximum intensity of 5 arcsec. The morphology of the X-ray
emission matched well to that of the radio emission at the same epoch. The jet
moved by 0.52 +/- 0.13 arcsec between 11 March and 19 June 2002. The apparent
speed during that interval was 5.2 +/- 1.3 mas/day. This is significantly less
than the average apparent speed of 18.1 +/- 0.4 mas/day from 1998 to 2002,
assuming that the jet was ejected in September 1998, and indicates that the jet
has decelerated. The X-ray spectrum is adequately described by a powerlaw with
a photon index near 1.8 subject to interstellar absorption. The unabsorbed
X-ray flux was 3.4 x 10^-13 erg cm^-2 s^-1 in the 0.3-8 keV band in March 2002,
and decreased to 2.9 x 10^-13 erg cm^-2 s^-1 in June. We also detect X-rays
from the eastern jet in March 2002 and show that it has decelerated and dimmed
since the previous detections in 2000.
