Development at the University of North Dakota of a Digital Thermosonde Instrument for the Study of Atmospheric Optical Turbulence

Atmospheric optical turbulence affects the transmission of electromagnetic waves between the Earth’s surface and orbit. High optical turbulence results in noisier ground to satellite communication and degraded satellite images. Optical turbulence profiles can increase the quality of Earth surface images obtained from satellites and stellar object images taken from ground telescopes. A NASA Undergraduate Student Instrument Project (USIP) at the University of North Dakota constructed a balloon-borne digital thermosonde instrument to measures high-resolution temperature differences using fine-wire platinum thermocouples. The digital thermosonde designs are based on the design originally developed by NASA in the 1970s and improved on by the Air Force Research Laboratory. Two tethered balloon flights indicate that the thermosonde can measure atmospheric temperature differences that agree with the low-end temperature differences derived from National Weather Service sounding data. A free flying balloon flight obtained similar refractive index structure parameter profiles from the thermocouple and the Graw radiosonde. The thermosonde horizontal temperature differences are similar to the vertical temperature differences measured by the radiosonde. The differences between the refractive index structure parameter profiles from the thermocouple and the radiosonde are consistent with values obtained by previous studies.