b'INTERNATIONAL WATERSChallenging Environment Calibrating the sensors for the EXO sondesAt each site, they profile conductivity, temperature may be easy, but the life of an instrument in theand salinity of the water column with two Baltic sea is anything but. instruments, including a SonTek CastAway CTD, a baseball-sized instrument that can be quickly cast "The Baltic Sea is a brackish water basinto the bottom and retrieved with a simple reel. with large vertical and horizontal gradients,"The maintenance visits also provide a chance for Lindfors explains. "Therefore, a selectedthe group to collect and analyze water samples for monitoring device must be able to handle biglaboratory-based verifications.temperature and salinity variations. In addition, a long ice-covered period brings challengesEven after enduring Baltic winters, during which to monitoring. Systems need to run severalwater temperatures can fall to -0.2 or -0.3 months without maintenance, and the presenceCelsius (31.4 Fahrenheit), the EXO sondes have a of drifting ice makes it impossible to use anyremarkable track record for delivering extensive telemetry systems. Therefore, monitoring islogs of water quality data for scientists.based on stand-alone sensors." Lindfors and his team pull each EXO to the surface approximately every three monthsthe gap widens to four or five months when the sea is frozen over. During the quarterly visits, they download logged data and change outCASTAWAY-CTD instruments for replacements calibrated in the Key featureslab and equipped with fresh batteries. Highly accurate sensors Salinity accuracy: 0.1 PSU Temperature accuracy: 0.05CWireless data transfer Integrated GPSFor more on the CastAway:Compact sizeSonTek.com/castaway-ctdThe right tool for the job. Like you, our engineers and scientists have spent years in the field, developing and using the products we design.That passion has culminated in the EXO Platform, a smart and field-ready water monitoring system. Offering a wide range of capabilities to those dedicated to measuring natural aquatic environments such as oceans, estuaries, rivers, lakes and ground water.For more on the EXO Platform: YSI.com/EXOWhos Minding the Planet? 41'