Design and Performance Test of Drifter Buoy

Abstract

The modern drifter buoy is a high-tech version of the "message in a bottle". It consists of a surface buoy and a subsurface drogue, attached by a long, thin tether. The buoy measures temperature and other sea/air properties, and has a transmitter to send the data to passing satellites. Drifters buoy for oceanographic research in the field had long been developed, but the design and construction of this instrument is still on going process. The major goal of the drifter intended by the designers of the drifter are cheap, lightweight and stable on several conditions. This study attempted to produce a drifter system capable of measuring position, speed and direction of surface current using a microcontroller, GPS and GSM technology as the data transmitter and receiver. There are 3 main parts of the drifter. They are the electronic systems, software and vehicles. Electronic systems are built from the microcontroller ATmega32, storage SD / MMC cards, transmission using GSM modem, GPS as a sensor position and velocity, and DALLAS DS18B20 as temperature sensors. The software is divided into 2 parts: software that is embedded into vehicle and software to control and receiving data in ground segment. Vehicle is divided into 2 main parts, first is float to house electronics system and drogue to maintain a position of drifter from the influence of surface wind. GPS used has a precision of 10 m, therefore the determination of position requires a certain time interval, this interval is very dependent on the speed of surface currents in the area. The results of performance test systems in the field showed that the design is able to record 95% -99% of the data successfully at 64 bps transfer speed. Field trial results also showed 85% and 93% successful data transmission using the GSM network with the power used in these systems totaling approximately 541-544 mW. The value of drag area ratio is 53.38, greater than 40 indicates that the drifter is produced has a pretty good ability to follow the movement of the water. In Pelabuhan Ratu, a different current direction at the center and edge of the bay. In the middle of the bay, when the water toward to lowest ebb the current direction towards to west and then silently at the lowest ebb. Finally, when water level increase the curent direction toward to the north. On the eastern edge of the bay, when the water toward to the lowest ebb, the direction of ocean surface current sheading out the bay.

Modern Drifter buoy adalah versi teknologi tinggi dari “pesan dalam botol” dimana alat tersebut terdiri atas surface buoy dan subsurface drogue yang mampu melakukan pengukuran terhadap posisi, suhu dan faktor fisik lain dan data tersebut dikirimkan melalui satelit. Rancangan drifter yang murah, ringan dan stabil merupakan beberapa syarat yang dituju oleh para perancang drifter. Penelitian ini bertujuan menghasilkan desain dan konstruksi sistem drifter buoy untuk perairan pesisir dan mendapatkan data pengamatan drifting buoy yang handal/berkualitas. Perancangan dan pembuatan sistem serta analisis data pada penelitian ini dilaksanakan di laboratorium Instrumentasi dan Telemetri Kelautan Bagian Akustik dan Instrumentasi Kelautan Departemen Ilmu dan Teknologi Kelautan Institut Pertanian Bogor, sedangkan uji coba lapang akan dilakukan di teluk Pelabuhan Ratu Provinsi Jawa Barat, dilaksanakan pada tanggal 28 dan 30 Agustus 2010. Beberapa tahap yang dilakukan dalam penelitian ini yaitu tahap perancangan perangkat keras, perancangan wahana, perancangan perangkat lunak, uji coba laboratorium, uji coba lapang dan analisis data. Perangkat keras terdiri atas mikrokontroler sebagai pusat pengendali menggunakan ATMega32, GPS sebagai sensor posisi, DS18B20 sebagai sensor suhu, Modem GSM sebagai transceiver dan media penyimpanan data SD/MMC card. Wahana buoy dibuat dari buoy polyprophelene yang dimodifikasi terdapat tiang untuk penempatan GPS dan antenna GSM, dibagian bawah terdapat sensor suhu. Pelampung ini disambungkan dengan drogue yang disetiap ujungnya dipasang besi melingkar untuk mempertahankan bentuk. Di bagian darat (penerima) dibuat perangkat lunak penerima dengan komputer dan modem GSM sebagai perangkat keras.