Research On Detection Of Submarine Through Short Scale Ocean Waves Using A Streak Tube Imaging Lidar

The sea surface wave plays an important role in the area of oceanography.Especially, the research on sea surface waves widely attracts the attentions of manycountries. As lots of information contained, it has become the focus of manyinstitutes all over the world. Through the detection of sea waves, people can extractmuch information of ocean currents, landscape under oceans, sea wind, submarineand so on. No doubt it must be an effective and valuable to recognize the oceanthrough the detection of sea waves.Among the large amount of information, the searching and extracting ofinformation caused by underwater submerged body’s moving will be a new methodto detect the submarine indirectly. The submarine has always drawn the attention ofNavy as its ability of hiding and attacking, especially, hidden in the shallow sea thatposes a great threat to the harbor and ships. According to this background, a newand effective method for detection of submarine is quite required. In this paper, weproposed a new antisubmarine method which was based on our theoretical andexperiment research.Firstly, we has analyzed and compared with kinds of methods for detectingsubmarine.(1) Traditionally, the method of using sonar to detect submarine has bigproblems because of the development of the mute technology. Especially, in theshallow sea, the sonar is affected by environment noise hardly, results in the lowSNR.(2) The magnetic detection of submarine has low efficiency because of thesmall detection zone. And it can be easily affected by geomagnetic field and others.(3)Infrared detection of wake flow has always been affected by ocean infraredradiation, and the small change of temperature among the large sea area increasesthe difficulty in this method of submarine detection.(4) Synthetic Aperture Radar(SAR) can effectively detect the ocean waves, but not the short scale waves becauseof its low resolution. Therefore, we proposed that we could use Streak Tube ImagingLidar (STIL) to detect of submarine wake flow because of its high sensitivity andrange resolution.Secondly, we have introduced the imaging principle of STIL. It could detect thephotons at different time and supply the range and intensity information. The rangeresolution can be “centimeter-level”. According to the research on this method, wethought that there would be3parts in this work:(1) The process that the submarineunderwater causes the internal waves and changes the ocean surface waves field.(2)The reflection of laser by ocean surface.(3) The process that the lidar detects the changes on the ocean surface caused by the submarine. These three processes canprove it is feasible that using a STIL to detect the submarine wake flow.In this paper, we based on the principle of hydrodynamic and simulated thewave height when the submarine was driving under the sea. We built the model ofsubmarine using the software of Gambit. Through this model, we used software ofFluent to simulate the wave height of the submarine wake flow. And we modulatedthis wake flow on the ocean surface model based on P-M spectrum. It would be thebase of the detection of submarine wake flow.In this paper, we chose plane as the platform of STIL. And we had discussedthe3-D resolutions of STIL. Based on the lidar equation, we get the reflectivity ofocean surface and calculate the echo energy. This process is the important hardcore.And we have built the experiment equipment of STIL and test the sensitivity andrange resolution. It could prove that STIL has the ability to detect the short scaleocean waves through our theoretical and experiment research.Based on the simulation and calculation above, we did many experiments in theYellow Sea, Bohai Sea and South China Sea through the STIL equipment we built.And we got the real streak imaging of ocean waves as the high resolution of STIL.Especially, we detected the short scale ocean waves whose wave height is about20centimeters and get the curve of single frame of waves. Compared with the oceansurface, we can recognize the submarine wake flow. So it is feasible to detectsubmarine wake flow using a STIL on the platform of plane.Based on the calculation, the simulation and experiment results above, weproposed the extraction method to extract the range and intensity information ofocean surface waves. And we discussed the influencing factors of detection ofsubmarine wake flow using a STIL. Finally, we got the application conditions of thismethod.