  The spatial structure of the emission lines and continuum over the 50
arcsecond extent of the nearby, O-rich, planetary nebula NGC 7009 (Saturn
Nebula) have been observed with the MUSE integral field spectrograph on the ESO
Very Large Telescope. Science Verification data, in <0.6 arcsecond seeing, have
been reduced and analysed as images over the wavelength range 4750-9350A.
Emission line maps over the bright shells are presented, from neutral to the
highest ionization available (He II and [Mn V]). For collisionally excited
lines (CELs), maps of electron temperature (T_e from [N II] and [S III]) and
electron density (N_e from [S II] and [Cl III]) are available and for optical
recombination lines (ORLs) temperature (from the Paschen jump and ratio of He I
lines) and density (from high Paschen lines). These estimates are compared: for
the first time, maps of the differences in CEL and ORL T_e's have been derived,
and correspondingly a map of t^2 between a CEL and ORL temperature, showing
considerable detail. Total abundances of He and O were formed, the latter using
three ionization correction factors. However the map of He/H is not flat,
departing by ~2% from a constant value, with remnants corresponding to
ionization structures. Ionization correction factor methods are compared for O
abundance, but none delivers a flat map. An integrated spectrum over an area of
2340 square arcseconds was also formed and compared to 1D photoionization
models. The spatial variation of a range of nebular parameters illustrates the
complexity of the ionized media in NGC 7009. These MUSE data are very rich with
detections of many lines over areas of hundreds of square arcseconds and
follow-on studies are indicated. (Abridged)
