RAMAN-shifted backscatter of laser radar radiation from atmospheric constituents in the troposphere has been reported1-3. Signals from nitrogen have been detected up to heights of about 6 km and there have been indications of backscatter at even greater heights4. Oxygen and water vapour have also been the subject of tropospheric Raman investigations, generally using frequency doubled ruby (0.3472 µm) as the laser transmitter.