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JAMSTEC 2002 Annual Report Marine Technology Department ated vehicles and deployed observation systems using acoustic signals. This fiscal year, we created demodulation software that applies multi-channel DFE (Decision Feedback Equalizer), which can utilize the space diversity effect, to facilitate communication under environments that contains a large multi-path mix. Sea trials carried out in Suruga Bay showed that demodulation is possible using -QAM multi-channel DFE demodulator, even when there is a large multi-path. Figure shows the channel characteristics through chirp pulse correlated value, and Figures and Correlated value 110 100 90 80 70 60 50 40 30 20 10 Direct wave Reflected wave 0 14 15 16 17 18 19 20 Time [ms] Fig. 1 Channel characteristics measured using chirp pulse Constelation in training mode 4 2 0 -2 -4 -4 -2 0 2 4 Constelation in decision oriented mode 4 2 0 -2 -4 -4 -2 0 2 4 show demodulation results. From Figure we can see that a multi-path (in this sea trial, it is a bottom reflected wave) of about % of the direct wave is received about ms after the direct-path. Under such environment, when using a single-channel receiver, errors arise as indicated in figure . If data are demodulated using a two-channel receiver, the space diversity effect will enable error-free data to be received as in Figure . (d) Measurement and sensor technology A great deal of effort is required by operators to control AUV attitude in marine research. As AUVs become more highly functional, there is a greater need to incorporate various automatic functions using highprecision sensors and powerful computers to enhance control over their movement. In this research we are developing sensors capable of measuring underwater movement with a high degree of precision. For ring laser gyros developed as a part of this research, we adopted conditions used for aircraft in environmental endurance. Conditions for aircraft require much tougher environmental performance than conditions used for ROVs, so in fiscal we improved the performance of the gyros by modifying a part of the environmental conditions so they conform with the condi- Constelation in training mode Constelation in decision oriented mode 4 2 0 -2 -4 -4 -2 0 2 4 4 2 0 -2 -4 -4 -2 0 2 4 MSE [dB] 0 -10 -20 MSE [dB] 0 -10 -20 -30 0 1000 2000 3000 4000 5000 6000 7000 8000 Time [symbols] Fig. 2 Demodulation example (single element, error: 1.2x10 -3 ) -30 0 1000 2000 3000 4000 5000 6000 7000 8000 Time [symbols] Fig. 3 Demodulation result (two elements, error free) 26
Japan Marine Science and Technology Center Marine Technology Department stratospheric platform airship prototype, and confirmed that it operates without any problems (Fig.). (3) AUV research and development From Fiscal Autonomous Underwater Vehicles (AUVs) are unmanned submersibles capable of cruising underwater independently according to a preset schedule program. Through this research, the Department is developing important key technologies, power source and navigation system for AUV. JAMSTEC completed ocean-going AUV in , the major principal particulars and external view are shown in Table and Fig. respectivity. The AUV was named URASHIMA, and sea trials began in fiscal . (Hereafter, called AUV). The AUV has capabilities of maximum operational depth of ,m, a cruising speed of kn, and a cruising range of km. The body is cylindrical to minimize drag force in advance. A high-performance power source and navigation system are essential to Table 1 URASHIMA specifications tions used in ROVs. In fiscal we produced an addition gyro to that produced in fiscal , and carried out tests on incorporating it in the inertial navigation system. The tests resulted in a performance of less than a half of the previous performance. (2) Research on ocean observation sensors for mounting on the stratospheric platform airship system From Fiscal We are carrying out research aimed at deploying an unmanned airship equipped with communication systems in the stratosphere at an altitude of about km for use in communication, broadcasting and global observation. It was decided that as a part of the initial plan, stratospheric trials would be carried out as a millennium project. JAMSTEC was responsible for the mission test, and developed the mission equipment (air sampling and measuring system) for the stratospheric platform airship prototype. We will mount this system in the airship prototype to take direct measurements of atmospheric CO up to the stratosphere, and take air samples. In fiscal we produced instruments based on prototypes produced the previous year, and confirmed through simulation that atmospheric CO can be readily measured under the assumed environments. We also fitted this measuring system on an aircraft for high-altitude trials, and obtained some excellent results. In addition, we carried out tests on connecting the measuring system to the Fig. 4 Air sampling and measuring system fitted on the airship Dimensions Maximum Range Maximum Depth Cruising Speed Navigation Operation Mode Sensors Length 10 [m] Width 1.3 [m] Height 1.5 [m] Weight 7/10 [ton] 300 [km] (Fuel Cell) 100 [km] (Lithium ion battery) 3,500 [m] 3 kn (Maximum 4 kn) Inertial Navigation System Doppler Sonar Homing Sonar Autonomous Remote (Optical, Acoustic) Side Scan Sonar Snap Shot Digital Camera Forward Looking Sonar CTDO (Conductivity, Temperature, Depth, Dissolved Oxygen) 27
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