Radar signal spectrograph
From AMS Glossary
radar signal spectrograph
(Abbreviated RASAPH; obsolete.) Analog radar device used in the 1950s to provide the power spectrum of the fluctuations in the received signal intensity, which may be interpreted in terms of the relative velocities among the scatterers in the pulse volume.
This approach was made obsolete when pulsed Doppler radar was introduced to meteorology in the late 1950s.