The foil cloud experiment: Some results obtained during the Energy Budget Campaign November 1980

An experiment for measuring local wind speed and direction in the altitude range from 94 to 70 km is described. Radar reflecting strips are ejected backwards opposite to the direction of rocket flight. A tuned system of overpressure in the storage canister and gas jets at the end of the canister help separate the individual strips from each other, compensate centrifugal forces caused by the spin of the rocket, and generate a density distribution inside the cloud which increases towards its center. This density compensates the effect of diffusion of the foils during descent. A larger height coverage is obtained than with ordinary chaff, provided that no violent wind shears are present. During disturbed conditions the cloud descends much faster than expected in a narrow interval near 80 km, and indicates an ascending motion between 72 and 74 km. Deviations from a smooth track are small, but more frequent than during calm conditions.