The Cornell University Portable Radar Interferometer (CUPRI) provided nearly continuous monitoring of the mesospher above Esrange, Sweden during the noctilucent cloud rocket and radar campaign of the summer of 1991 (NLC-91). CUPRI probed the mesosphere above Esrange from 78 to 91 km altitude with 300-meter resolution and was sensitive to the enhanced Polar Mesospheric Summer Echoes (PMSE) that occur in the same altitude range as NLC formations. Out of the total of 264 hours of CUPRI observation time, PMSE were present for 140 hours. Rocket Salvo A was flown on the night of August 9--10 into an NLC event that occurred simultaneously with a thin and weakening PMSE layer. High-resolution Doppler spectrograms of this PMSE event revealed sawtooth-like discontinuities at ~83 km alitude, which we interpret to be a distorted partial reflection layer which was advected across the radar beam. ¿American Geophysical Union 1993