Doppler spectrum of the Hartley grain-coma echo, averaged over all CW observations from 2010 October 24 to 30. The nucleus has been subtracted from this spectrum by interpolation. Shown are both circular polarization components: OC (solid) and SC (dotted). The spectra have been smoothed and decimated to 5 Hz resolution. Also shown is model fit (dashed) to the OC spectrum based on a 90° wide grain-ejection fan (see the text).