  We present the results of deep X-ray and gamma-ray observations of the
Geminga pulsar obtained in the final years of the ASCA and CGRO missions, and
an upper limit from RXTE. A phase-connected ephemeris from the gamma-rays is
derived that spans the years 1973-2000, after allowing for a minor glitch in
frequency of Delta f/f = 6.2 x 10^-10 in late 1996. ASCA observations of the
hard X-ray pulse profile in 1994 and 1999 confirm this glitch. An improved
characterization of the hard X-ray pulse profile and spectrum from the long
ASCA observation of 1999 confirms that there is a non-thermal X-ray component
that is distinct from the gamma-ray spectrum as measured by EGRET. It can be
parameterized as a power-law of photon index Gamma = 1.72 +/- 0.10 with a flux
of 2.62 x 10^-13 ergs/cm^2/s in the 0.7-5 keV band and pulsed fraction 0.54 +/-
0.05, similar to, but more precise than values measured previously. An
extrapolation of this spectrum into the energy band observed by the RXTE PCA is
consistent with the non-detection of pulsed emission from Geminga with that
instrument. These results are interpreted in the context of outer-gap models,
and motivations for future X-ray observations of Geminga are given.
