INVESTIGATION OF UPPER ATMOSPHERIC TURBULENCE

The experiment was aimed to estimate the parameters of homogeneous, isotropic optical turbulence in the upper atmosphere.

The payload consisted in an array of 13 anemometers placed in a plane on the perimeter of a hexagonal grid, with two additional sensors placed on two arms extending from the hexagonal array for a total of 15 sensors. The locations of sensors were chosen to approximately evenly sample the autocorrelation space of the temperature fluctuations. The sensor array was suspended under the gondola, several centimeters below the hexagonal ring to minimize the turbulent interference during the descent.

In addition to the high resolution temperature sensing package, the balloon was instrumented with a three axis attitude sensing package, a pressure sensor, a global positioning system, and an ambient temperature sensor. The attitude sensing package allowed the temperature measurements to be registered in three dimensional space if the balloon swinged or rotated. The pressure sensor was required because the atmospheric pressure varied significantly over the balloon flight, and index of refraction fluctuations are function of both temperature and pressure. All of the high resolution temperature data and the auxiliary data was transmitted to the ground in real time and recorded on magnetic tape drives.

The entire package weighted around 700 kg.

Balloon launched on: 8/20/2000
Launch site: Holloman Air Force Base, Alamogordo, New Mexico, US Nenninger Site
Balloon launched by: Air Force Research Laboratory (AFRL)
Balloon manufacturer/size/composition: Zero Pressure Balloon Winzen - 17.000 m3 (1.5 mil)
End of flight (L for landing time, W for last contact, otherwise termination time): 8/20/2000
Landing site: White Sands Missile Range, New Mexico, US
Payload weight: 700 kgs

The balloon was launched from Holloman AFB on the early morning on August 20, 2000. Due to the sensitive nature of the probes, the entire flight was conducted at night over the White Sands Missile Range with no cloud cover. The original flight plan called for the balloon to ascend to approximately 21 kilometers and release helium to begin a controlled descent at a rate of 4 m/s to an altitude of 10 kilometers. At that point, ballast was to be dropped so that the balloon would rise, and the flight profile repeated. Due to the failure of the ballast release mechanism, only one controlled descent was possible, lasting approximately 150 minutes. Also, one of the two digital transmitters failed and a probe was corrupted by noise preventing the experimenters from collecting data from eight of the probes. However, they did collect data from seven probes.

• Experimental estimation of the spatial statistics of turbulence-induced index of refraction fluctuations in the upper atmosphere Applied Optics Vol. 40, Issue 12, pp. 1863
• Experimental Investigation of Upper Turbulence Models Final report, Michigan Technological Univ. Houghton