This research will develop and test "smart" balloons whose altitude can be controlled to provide the capability to follow isentropic, constant pressure surfaces or other chosen strategies. In addition to providing track information through Global Positioning System (GPS) derived position data, the smart balloons will carry pressure, temperature and humidity sensors, and these data will be transmitted along with the position data. By including pressure and temperature sensors and a pressure pump, the smart balloon can be programmed to track along isentropic, moist isentropic, isopycnic or constant pressure surfaces. The ballasting of the smart balloon will be achieved using an helium filled, expandable balloon inside an air-filled constant-volume, pressurized balloon. If a higher altitude is required during an experiment, air is released from the pressurized outer balloon. This action allows the helium-filled inner balloon to expand and take the place of the heavier released air. If a lower altitude is desired, outside air is pumped into the outer balloon, which increases its density and causes the balloon package to decrease in altitude. The virtue in development of this capability is that the instrumented smart balloons can be utilized in a number of observational applications including: Lagrangian observational strategies, or in prescribed sounding strategies, without the threat of balloon loss through groundings. Smart balloons capitalize on recent technological advances to provide a cost-effective, new data gathering capability for the atmospheric sciences research community. Such balloons, or tetroons, can be deployed during field experiments directed at investigation a variety of research problems ranging from storm structure to atmospheric chemistry in the troposphere and stratosphere. In situ observational data for the previous seven hours are transmitted at five minute intervals on UHF along with GPS position of the tetroon. These da ta can then be intercepted by receivers on-board research platforms within approximately one hundred miles of the tetroon.
