  The X-ray nova XTE J1118+480 suffers minimal extinction (b = 62 degrees) and
therefore represents an outstanding opportunity for multiwavelength studies.
Hynes et al. (2000) conducted the first such study, which was centered on 2000
April 8 using UKIRT, EUVE, HST and RXTE. On 2000 April 18, the Chandra X-ray
Observatory obtained data coincident with a second set of observations using
all of these same observatories. A 30 ks grating observation using Chandra
yielded a spectrum with high resolution and sensitivity covering the range
0.24-7 keV. Our near-simultaneous observations cover approximately 80% of the
electromagnetic spectrum from the infrared to hard X-rays. The UV/X-ray
spectrum of XTE J1118+480 consists of two principal components. The first of
these is an approximately 24 eV thermal component which is due to an accretion
disk with a large inner disk radius: > 35 Schwarzschild radii. The second is a
quasi power-law component that was recorded with complete spectral coverage
from 0.4-160 keV. A model for this two-component spectrum is presented in a
companion paper by Esin et al. (2001).
