A description is given of the design of an instrument which has been built to detect the lithium 671 nm line against the daytime sky continuum. The instrument covers the field of view by means of a servocontrolled scanning mirror and detects the lithium line by chopping the received beam and using phase sensitive detection. Data obtained for a daytime release of lithium between 90 and 130 Ian altitude are presented, and the methods for the analysis of these data to obtain a wind profile of the upper atmosphere are described. The derived wind profile is similar in its main features to those observed at twilight and night.

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