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We have built and tested two autonomous ozone measurement systems for use on ocean buoys and towers. They are based on low-power atmospheric ozone sensors from Physical Sciences Inc. (PSI) and 2B Technologies. The PSI sensor operates at 1 Hz with a precision of 1 ppb, but requires about 45 W with the present data system; the 2B makes a measurement every 10 seconds with a precision of 1-2 ppb and uses less than 4 W. The sensors have been packaged in watertight enclosures, with a set of valves and filters to keep out seawater and aerosols. A controller uses data from the sensors and a meteorological system to determine whether sampling should proceed. If a sensor malfunction (such as an incorrect valve position or a temperature beyond its proper range) is detected, the controller attempts to correct it. Both sensors have been tested and used over the ocean, and one complete ozone measurement system (with the PSI sensor) has been successfully deployed on a buoy off Woods Hole. In 2003, this system was operated at the Chesapeake Bay Lighthouse Tower for over a month with excellent results. The2B system was also successfully tested in 2003, at a nearby offshore tower. The design of the systems and their testing and deployments are described, and data from some of the first experiments are presented.

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The Vector Measuring Current Meter (VMCM), developed by Drs. Robert Weller and Russ Davis and commercially produced by EG&G Sealink Systems, has proven itself over many years as the instrument of choice for accurate velocity measurements in the upper ocean, especially when used on a surface mooring. The Upper Ocean Processes (UOP) group at the Woods Hole Oceanographic Institution (WHOI) is presently in the process of upgrading the existing inventory of VMCMs. This project was undertaken because the VMCM and most of its electronic components are no longer commercially available and because replacement for the Sea Data Corp., data reader and 4-track cassette reader are no longer available. The firmware control of the VMCM makes it virtually impossible to add additional sensors to the existing instruments. By upgrading the VMCM with a flexible data loggerkontroller, they will continue to be a viable instrument. VECTOR MEASURING CURRENT METER (VMCM) OVERVIEWThe Vector Measuring Current Meter (VMCM) was developed in the late 1970s by Drs. Robert A. Weller and Russ E. Davis and in the 1980s was commercially available from EG&G Sealink Systems. Figure 1 shows a VMCM housed in its load cage. The VMCM has two orthogonal cosine response propeller sensors that measure the components of horizontal current velocity parallel to the axles of the two propeller sensors. The orientation of the instrument relative to magnetic north is determined by a flux gate compass. East and north components of velocity are computed, averaged and stored on cassette magnetic tape.The VMCM is the current standard for making high quality velocity measurements in near-surface regions. Figure 2 compares the published test data from Aanderaa, VACM, and electromagnetic current meters with data from the VMCM and ACM. Based on the intercomparison of the test data, the VMCM sensor will introduce the least error in relatively small mean flows when high frequency oscillatory flow is also present. Davis 1980, and Halpern et al. 1981).The propeller sensor assembly, commonly referred to as the "sting", has undergone a number of changes that have improved its long-term performance. The orig~nal propellers were subject to blade breakage. Several years ago a new material was selected for injection molding the propeller camponents and since that time there has not been any breakage. Early on the propeller bearings were a source of failure. After considerable testing the bearings were upgraded to silicon nitride, and as a result of this change there have not been any bearing failures. In fact several stings, outfitted with silicon nitride bearings have been deployed with the same bearings for a total of two years without any noticeable degradation in the bearing.The Sony magnetodiodes used on the rotor sensing circuitry have been replaced by Hall-effect sensors. These changes have resulted in a propeller sensor subassembly that is extremely reliable, has measurement dynamics that are well understood, and has collected the highest quality data possible in the upper...