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Thirteen minutes after sunrise on September 30, 2013,16.5 m deep in northern Monterey Bay, a white shark (Car-charodon carcharias) struck the MBARI long-range autonomous underwater vehicle (LRAUV) Tethys and left bite grooves in the pressure vessel and tooth fragments embedded in the aft fairing. Tethys survived the attack and continued her mission measuring ocean properties in that area for another week. The operators did not know about the strike until recovering the vehicle normally at the end of the deployment, when the tooth fragments and apparent bite diameter provided sufficient information to identify the shark species. We discuss the motion of the vehicle during the strike, its control response after being released by the shark, and the environmental properties it measured near the time of the strike. We also provide a damage report — although Tethys was able to complete her mission after the strike, she did not get away without a scratch. This event is a good example for recent work aimed at detecting faults and performance anomalies onboard in realtime so that operators can be notified. We show that a statistical anomaly detector correctly identifies the strike and effectively highlights it as unexpected behavior for the operator to review.

In this note we examine the relationships between a subnormal shift, the measure its moment sequence generates, and those of a large family of weighted shifts associated with the original shift. We examine the effects on subnormality of adding a new weight or changing a weight. We also obtain formulas for evaluating point mass at the origin for the measure associated with the shift. In addition, we examine the relationship between the measure associated with a subnormal shift and those of a family of shifts substantially different from the original shift.

This paper presents the development effort toward demonstrating acoustic tracking and homing with a long-range AUV (LRAUV) at the Monterey Bay Aquarium Research Institute (MBARI). The acoustic tracking system uses a directional acoustic transponder (DAT) from Teledyne Benthos, backed by an acoustic baffle made from syntactic acoustic damping material (SADM). We discuss sensor integration into the LRAUV system, procedures and results from an in-house calibration, and field tests with both anchored and towed transponders.

The autonomous localization and tracking of the center of a phytoplankton bloom patch by the Tethys Autonomous Underwater Vehicle (AUV) is introduced. This capability is motivated by the desire to separate temporal variability from spatial variability in the observation of phytoplankton dynamics. In effect, by observing the organisms in their own reference frame, we isolate their temporal variability. The small spatial scales and the high temporal variability of phytoplankton patches make strategies that rely on human control challenging, as these strategies must contend with the high latency of intermittent low-bandwidth communications between the submerged AUV and an operator. The autonomous capabilities demonstrated here make much greater use of the responsiveness of the AUV platform to minimize the chance of losing track of the patch and maximize the rate at which the patch center is revisited.

The Tethys autonomous underwater vehicle (AUV) is a 110 kg vehicle designed for long-range, high- endurance operations. Performance goals include supporting a payload power draw of 8 W for a range of 1000 km at 1 m/s, and a power draw of 1 W for 4000 km at 0.5 m/s. Achieving this performance requires minimizing drag and maximizing propulsion efficiency. In this paper, we present the design of the propulsion system, explore the issues of propeller-hull interactions, and present preliminary test results of power consumption and efficiency. In recent underwater experiments, the propulsion system's power consumptions were measured in both Bollard pull tests and during the vehicle's flights. Preliminary results of power consumptions and efficiency are shown to be close to the theoretical predictions.

Thermoclines play a key role in ocean circulation, marine ecology, and underwater acoustics. In oceanographic surveys, it is often desirable to detect the thermocline and track its spatio-temporal variation. Mobility of an autonomous underwater vehicle (AUV) makes it an efficient platform for thermocline tracking. In this paper, we present a fully autonomous algorithm for detecting and tracking the thermocline by an AUV. The key is detection of the peak gradient of temperature. We have tested the algorithm by post-processing data from a previous Dorado AUV survey over the northern Monterey Bay shelf. We are in preparation for field tests of the algorithm on the newly developed long-range AUV Tethys.

The Monterey Bay Aquarium Research Institute (MBARI) has developed an AUV docking station for a 21-inch (54 cm) diameter AUV. The system was designed for operation with cabled undersea observatories in water depths up to 4 km deep and has been demonstrated in the open ocean, though at much shallower depths. The program demonstrated successful autonomous homing and docking, data downloads, uploading of new mission plans, battery recharging, and complete power cycling of the AUV. We describe the design, and at-sea tests.

We prove that two automorphisms of L??-spaces are conjugate if and only if certain related operator algebras are algebraically isomorphic. This extends a result of W. Arveson by dropping the assumptions that the automorphisms are ergodic and measure-preserving. W. B. Arveson [1] first looked at the conjugacy problem for automorphisms of measure spaces in terms of operator algebras. Suppose (X, ,u) is a finite measure space and a is an ergodic measure-preserving automorphism of L? (,u) . Arveson [1] showed that the Banach algebra of operators on L2(X, u) generated by the unitary operator Ua of composition with a, together with the multiplications by L? (X, ,u)-functions, classifies a in the sense that two such automorphisms are conjugate if and only if the associated algebras are unitarily equivalent. Later, Arveson and K. B. Josephson [2] extended this result by showing that the algebras need only be isomorphic. This was proved not in the setting of measure-preserving automorphisms but of homeomorphisms on locally compact spaces. The Arveson-Josephson result was later extended by J. Peters [4] using semi-crossed products. In [3] the present authors associated with each homeomorphism on a compact Hausdorff space a family of algebras called conjugacy algebras. It was then proved that two homeomorphisms are conjugate if and only if some conjugacy algebra for the first is isomorphic to some conjugacy algebra for the second. The algebras considered in [1, 2], and [4] are conjugacy algebras, so the results in [3] include these. In this note, we return to the automorphisms of Arveson's original paper [1]. We show that two such automorphisms are conjugate if the corresponding algebras are isomorphic, and we do not need to assume that the automorphisms Received by the editors June 24, 1988. 1980 Mathematics Subject Classification (1985 Revision). Primary 28D05, 47D25; Secondary 46L40, 47D30.

A family of algebras is associated with each continuous map on a compact Hausdorff space. These algebras are called conjugacy algebras. It is shown that two continuous maps are conjugate if and only if some conjugacy algebra of one is isomorphic to some conjugacy for the other. Numerous examples of conjugacy algebras are provided.