Response of NBS microwave refractometer cavities to atmospheric variations

Abstract

The sampling cavity of the NBS refractome te rs has bee n e valuated in a wind tunnel , a wate r flow tunn el, and in the free atmos phere. The cavity is slightly velocity-sensitive. It is also as pectse nsitive, an error bein g introduced whe n the wind is oblique to the axi s of the cavity affecting th e level of th e s pec trum. Th e charac te ri stic flu shing length of th e cavity in normal operation is estimated as 0.75 meters whe n the wind is into the c avity and co nsid erably more whe n th e wind is at an oblique an gle. A modifi ed cavity has been de veloped whi c h a ppears to substantially impro ve the res ponse of the refractome te r.

Generation and dissipation of microwave refractive-index fluctuations in the boundary layer

“…The overall accuracy of the instrument is 0.1 N unit and it is capable of fully resolving refractivity variations separated by 0.75 m (Gilmer et al, 1965). Thermocouples consisting of welded, 2-rail copper-constantan junctions measure the air temperature.…”