We have developed and flown an experimental radiosonde payload which features a fast, high-sensitivity dewpoint hygrometer. This instrument achieves fast response to atmospheric humidity by using a surface acoustic wave (SAW) device to detect condensation with much higher sensitivity than conventional optical dew detectors. An early prototype showed more than an order of magnitude faster response than chilled-mirror hygrometers in tropospheric humidity measurements on the NASA DC8. For the radiosonde experiment, we miniaturized and integrated the SAW hygrometer into a 1 kg package that includes pressure and temperature sensors, GPS, a programmable instrument controller, and a high-speed radio modem. The JPL radiosonde is capable of both autonomous and interactive operations, with local intelligence and full duplex command and control functions. In April of this year, we flew this instrument to 44,000 feet, recording pressure, temperature, humidity, and GPS position during ascent and descent. Using a mobile ground station equipped with a second GPS receiver, the payload was recovered within an hour of landing, fifty miles from the launch site. The SAW hygrometer recorded frostpoint down to -76°C, with high correlation between ascent and descent data, despite the spatial and temporal separation of the data sets. A Vaisala RS80 radiosonde was flown on the same balloon for comparison, using a completely independent transmitter and ground station to record data during ascent only. Favored by dry conditions during the flight, the Vaisala humidity sensor showed excellent agreement with the SAW hygrometer.
The authors would like to acknowledge the NASA Atmospheric Dynamics and Remote Sensing Program for supporting this research program since its inception. The support of many individuals from NASA’s Wallops Flight Facility, New Mexico State University’s Physical Science Laboratory, and the Weather Support Branch, White Sands Missile Facility was essential in the planning and execution of the balloon flight. The research described in this abstract was performed at the Center for Space Microelectronics Technology, Jet Propulsion Laboratory, California Institute of Technology, and was jointly sponsored by the National Aeronautics and Space Administration, Earth Science Enterprise and Space Science Enterprise.
The 8th Conference on Aviation, Range, and Aerospace Meteorology