Size of the Vela pulsar's emission region at 13 centimeter wavelength

We present measurements of the size of the Vela pulsar in three gates acros s the pulse, from observations of the distribution of intensity. We calcula te the effects on this distribution of noise in the observing system, and m easure and remove it using observations of a strong continuum source. We al so calculate and remove the expected effects of averaging in time and frequ ency. We find that effects of variations in pulsar flux density and instrum ental gain, self-noise, and 1 bit digitization are undetectably small. Effe cts of normalization of the correlation are detectable, but do not affect t he fitted size. The size of the pulsar declines from 440+/-90 km (FWHM of b est-fitting Gaussian distribution) to less than 200 km across the pulse. We discuss implications of this size for theories of pulsar emission.