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We present the first direct ground based observations of important cometary plasma properties. We measured plasma velocities and temperatures both sunward and tailward of the nucleus of comet P/Swift-Tuttle in Novemeber and December of 1992. The observations are a series of long-slit high resolution spectra of the H$_2$O$^+$ emission centered at 6199\AA with a velocity resolution of about 7 km s$^-1$ (FWHM) and a spatial resolution of about 10$^4$ km at the comet. Emission is visible from just inside the predicted position of the cometopause on the sunward side of the nucleus out to $5 \times 10^5$ km on the tailward side. The shock heating and deceleration of the plasma on the sunward side is clearly observed as is the acceleration and heating into the tail. These observations show the effectiveness of ground based methods for the systematic study of cometary plasmas.
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