Diode Laser Hygrometer and Thermometer for Aerial Vehicles
An instrument that will perform rapid simultaneous measurements of water vapor and temperature on an aerial platform is being developed in this project. Water vapor concentration and ambient temperature are two critical parameters in any atmospheric model of weather or climate. Researchers want increased measurement speed to improve spatial resolution of data sets. The instrument being developed will measure water vapor at 50 Hz and temperature at 100 Hz. No instrument exists that can perform both measurements concurrently at these speeds. The project will build upon the VCSEL hygrometer that was developed by Southwest Sciences for the NSF G-V in 2007. A second laser will be added to perform fast optical thermometry based upon the optical absorbance of oxygen at 760 nm. The optical system will employ a multilaser, multipass optical scheme used on the Mars Curiosity Rover. Although the project targets an instrument for a jet platform such as the ARM Challenger 850 jet, the measurement approach can be applied to all types of aerial vehicles – manned aircraft, unmanned aircraft, and balloons. The main difference between instruments for these different platforms is the structural strength needed for the optical platform. During the Phase I project, the two beam optical system for the hygrometer/thermometer was demonstrated and used to perform oxygen measurements. Several types of absorption measurements were performed including one and two peak conventional absorbance measurements as well as wavelength modulation measurements. Single peak conventional absorbance spectroscopy was found to provide the best precision for the temperature measurement. Overall, the 100 Hz noise levels observed were 0.5 to 1.5 degrees K with a measurement accuracy of ~0.3 degrees. While the theoretical models relating temperature to oxygen absorbance proved to be inaccurate, empirical measurements showed that temperature is a single valued function of oxygen absorbance for a given pressure. This demonstration was performed over the range of conditions that are encountered during jet flight. These measurements form the basis for designing the jet thermometer/hygrometer instrument and are indicative of the precision and accuracy that the final instrument will display.
- Research Organization:
- Southwest Sciences, Inc., Santa Fe, NM (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- SC0021446
- OSTI ID:
- 1833000
- Type / Phase:
- SBIR (Phase I)
- Report Number(s):
- DOE-SWS-21446; 81.049
- Country of Publication:
- United States
- Language:
- English
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