  The experimental characterization of the spatial and temporal coherence
properties of the free-electron laser in Hamburg (FLASH) at a wavelength of 8.0
nm is presented. Double pinhole diffraction patterns of single femtosecond
pulses focused to a size of about 10 microns by 10 microns were measured. A
transverse coherence length of 6.2 microns in the horizontal and 8.7 microns in
the vertical direction was determined from the most coherent pulses. Using a
split and delay unit the coherence time of the pulses produced in the same
operation conditions of FLASH was measured to be 1.75 fs. From our experiment
we estimated the degeneracy parameter of the FLASH beam to be on the order of
$10^{10}$ to $10^{11}$, which exceeds the values of this parameter at any other
source in the same energy range by many orders of magnitude.
