Ionospheric winds measured by gun-launched projectiles

Project HARP (High Altitude Research Project) is using gun-launched projectiles to probe the upper atmosphere. Under this program, 130-mm projectiles have reached 70 km, and 420-mm projectiles have been placed 143 km over Barbados. The first experimental program for the 420-mm gun has been the production of luminous TMA trails for the measurement of winds above 90 km. This smoothbore extended gun is 36 meters long, weights 180 metric tons, and has flown vehicles that generate TMA trails from 90 km to 138 km. In the time period July 1964 to February 1966, forty-nine such nighttime trails have been photographed and twenty-nine of these analyzed. During twenty-two of these flights, concurrent ionosonde records have been taken, and the locations of sporadic-E layers have been determined for comparison with the wind profiles. The wind data analyzed showed little evidence for the Rosenberg suggestion that the wind vector rotates with increasing altitude. Nine direction reversals occurring in less than 3 km were observed, and fourteen layers of constant direction flow with thicknesses greater than 8 km were observed. A maximum wind speed of 147 m/sec was measured. The six trails of the night of September 20–21, 1965, showed a rapid variation of meridional component of wind at fixed altitude with peak-to-peak amplitude of over 200 m/sec. Sine waves were fitted to wind components at fixed altitude with fair-to-good standard deviations.