  We present new HST/WFPC2 imagery and STIS long-slit spectroscopy of the
planetary nebula NGC 7009. The primary goal was to obtain high spatial
resolution of the intrinsic line ratio [O III] 4364/5008 and thereby evaluate
the electron temperature (T_e) and the fractional mean-square T_e variation
(t_A^2) across the nebula. The WFPC2 T_e map is rather uniform; almost all
values are between 9000 - 11,000 K, with the higher T_e's closely coinciding
with the inner He^++-zone. The results indicate very small values - <~ 0.01 -
for t_A^2 throughout. Our STIS data allow an even more direct determination of
T_e and t_A^2, albeit for a much smaller area than with WFPC2. We present
results from binning the data along the slit into tiles that are 0.5'' square
(matching the slit width). The average [O III] temperature using 45 tiles
(excluding the central star and STIS fiducial bars) is 10,139 K; t_A^2 is
0.0035. The measurements of T_e reported here are an average along each line of
sight. Therefore, despite finding remarkably low t_A^2, we cannot completely
rule out temperature fluctuations along the line of sight as the cause of the
large abundance discrepancy between heavy element abundances inferred from
collisionally excited emission lines compared to those derived from
recombination lines.
