A role for high power millimeter wave sources in atmospheric remote sensing

Summary form only given. Applications of high-power radiation sources (gyrotrons) at 94 GHz to atmospheric sensing have been studied. Sources in the atmospheric window at 94 GHz are particularly useful for the remote sensing of clouds due to the fact that Rayleigh scattering from the droplets in the cloud have a cross section which is proportional to /spl lambdasup -4/. Earlier 94 GHz data on clouds were very limited because the transmitter average power was only 4 W. Gyrotrons have the capability of achieving at least two-orders-of-magnitude increase in average power. The quasi-optical gyrotron developed at NRL brings an additional capability of tunability. Tuning from 85-130 GHz has been demonstrated, and harmonic operation could open the possibility of tuning up to 260 GHz. Ground based radiometry in this frequency range has been extremely useful in detecting upper atmosphere trace elements. One possible application to remote sensing is the measurement of transmission of this radiation through the upper atmosphere.