5.10 A high-resolution temperature probe for airborne measurements

Tuesday, 16 January 2001: 10:45 AM
Jeffrey R. French, NOAA/ERL/ARL, Idaho Falls, ID; and T. L. Crawford, R. C. Johnson, and O. R. Cote

A new device for measuring temperature from an aircraft in clear air is being developed and tested. This instrument will measure temperature fluctuations near the top of the troposphere and in the lower stratosphere to determine the turbulent characteristics in this region of the atmosphere. It will provide a means to measure temperature fluctuations to 0.005 C with a response time of 0.02 s. To achieve such high resolution it is important that the probe is insensitive to slight changes in the airflow direction that may affect the recovery factor. Fluctuations in pressure (turbulence) must also be corrected for. This is accomplished by placing the sensing element near the back end of a conically-shaped, 20-cm long protective housing. The aluminum housing expands the flow, thereby slowing it to roughly 5% of its free-stream value. The housing is designed to be insensitive to flow direction, and thus the recovery factor remains constant. Pressure measurements inside the housing will verify the speed of the flow past the element, and correct for turbulent fluctuations if this proves necessary. To mitigate erroneous signal caused by mechanical strains on the element, a thermocouple is used as opposed to the more traditional thermal resistor.

Initial bench tests have proven to be very promising. Flight tests are scheduled for the end of July. Comparisons of data from this probe will be made with the Polish-designed Ultra-Fast Temperature (UFT) sensor. We will report on the design, construction, and initial testing of this instrument.

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