Frag Out! Magazine
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imaging and a LED lighting system to sup- port its performance. The Hugin vehicle can be operated in three modes: Ä supervised by an operator. This means that the crew of the mother ship is constantly able to give orders to the vehicle, change its tasks, and receive in- formation about its current position; Äin autonomous mode, in which the vehicle operates autonomously and inde- pendently of its carrier; Äin semi-autonomous mode, when tasks are carried partially autonomously and partially under human supervision. There are several ways to communicate with a vehicle carrying out a task. A sub- merged AUV can be contacted by means of acoustic communication – using a high-capacity uplink, a bidirectional data transmission link of a lower capacity, and – in emergency situations – through the HIPAP system (which is normally used for high-precision positioning of the vehicle); when the AUV is on the surface, contact is made by means of an UHF radio link and by Iridium satellite communication. The technically easiest communication solution is used when the vehicle is lifted out of the water and placed on board of its carrier ship. Then, the vehicle is con- nected to the carrier's combat system through an Ethernet port. One of the major challenges concerning operations carried out with the use of Hugin is the procedure of launching it from the ship to the water and recover- ing it onto the deck after the mission is complete. The system designed to han- dle both these tasks is a special sting- er (ramp) on which the vehicle rests. When the vehicle is launched, the system with the AUV extends almost complete- ly beyond the envelope of the stern and is tilted down – creating a ramp from which Hugin is released into the water. The recovery procedure is the reverse of the above steps. The AUV surfaces about 50–100 meters away from the ship. A recovery line is fixed to the vehicle. The line is used to pull it towards the lowered stinger. Next, the vehicle is pulled onto the stinger and lifted back onto the deck of the mother ship. DATA ANALYSIS The system is supplied with a dedicated software package. It enables process- ing and analyzing the collected material. These processes are carried out on three levels: Ä supply of raw sonar input material of the frequency of 100kHz; the material enables only a rough analysis and detec- tion of very large objects, such as ship- wrecks; Ähigh resolution – such imaging is the effect of raw material being "processed" and converted to the SAS standard, and is usually performed for the entire scanned surface of the seabed. The reso- lution of 4 cm makes it possible to detect even the smallest mines or other danger- ous objects; Äspot processing – the highest attain- able image resolution of 2 cm. It takes a lot of time because of the significant size of raw data, whose processing requires considerable computing power. On ac- count of the above, it is is usually used to deal only with objects and areas defined in the analysis of materials of lower qual- ity. It is not utilized too often because imaging in the resolution of 4 cm is nor- mally more than sufficient to carry out anti-mine operations. HUGIN WITHIN THE COMBAT SYSTEM OF THE KORMORAN The Kormoran minehunter is one of the units which are very well suited to com- bating contemporary mine threats. Its range of payloads includes a whole spec- trum of sensors fitted on the ship itself and on the unmanned vehicles carried on its deck. The unit features an SHL- 10/TM hull mounted sonar designed by Ośrodek Badawczo Rozwojowy Cetrum Techniki Morskiej [Research Center – Marine Technology Center]. The sonar makes it possible to scan the space un- der the bottom of the ship, but only to a certain depth, limited by water layers of different temperature levels. The sys- tem used to overcome this limitation is a Swedish ROV named Double Eagle Mk III, carrying an SHL-300 towed sonar. Thanks to SAAB's product, the sonar's antenna can be placed closer to the sea- bed, below particular water layers, and at some distance away from the ship, thus improving its security. The vehicle is controlled from the ship's deck by means of an umbilical cable, which means it's not an autonomous system, but one that re- mains constantly under the control of an operator. The third solution enabling mine threat detection is the abovementioned Hugin 1000 MR autonomous underwater ve- hicle, packed with a very broad range of features. It can be used for mine countermeasure purposes thanks to be- ing equipped with a HISAS 1032 sonar. The Hugin – HISAS duo has substantially increased the surface area that can be scanned by the carrier. This is possible thanks to the application of a synthetic aperture sonar operating in an appro- priate frequency range, fitted on an unmanned underwater platform able to operate close to the seabed within a sig- nificant range of depth ratings. Apart from the improved capacity, sea- men speak also highly of another major advantage of the said solution. Placing the sensors on board of an autonomous unmanned vehicle grants a high level of safety to the carrier and its crew, re- maining away from any potential threats the AUV may come across. One of the few disadvantages of using an www.fragoutmag.com