The System Design And Experiments Of The Airborne Fluorescence Ocean Lidar

Airborne ocean fluorescence lidar is an advanced technique in remote sensing scope. It has many advantages, such as its high efficiency, real time measuring and its measuring accuracy etc. With the improvement of the lidar technique and its increasingly broader applying prospect, in the year 2001, ORSI, OUC took on the item "Airborne ocean lidar oceanic environmental surveillance technique", which belongs to National 863 Resource and Environment technique field. Since then, ORSI has been developing the airborne ocean fluorescence lidar to measure the chlorophyll-a concentration in the sea surface. In November 2003, the Airborne ocean fluorescence lidar was installed on the China Marine Surveillance airplane B-3807, and its first aviation experiment was carried out successfully.This dissertation is based on the project, mainly consisted of four parts: First part is introduction which narrates the development history and basic principle of measuring chlorophyll-a concentration, actualities and development current of Ocean Lidar; The second part is the hardware design and construction of airborne Ocean Lidar; The third part is software design and the method of data processing; The last part is experiments and analysis of result of experiments.The introduction firstly introduces the theory of measuring chlorophyll-a concentration, then enumerates the applications of airborne ocean lidar on measuring depth of water, ocean zoology environment and verify of ocean color satellite. Then the development and actuality of ocean lidar are introduced. The airborne ocean lidar in developed country are advanced, but airborne ocean lidar in our country is just beginning. It should be developed fast to satisfy the need of ocean environment watching. At the end of the introduction, the trend of airborne ocean lidar in our country is indicated based on the domestic actuality of airborne ocean lidar.The second part includes the hardware design with the computer engineering theory, and mechanical structure design. The hardware of system includes laser transmit, fluorescence and Raman receive, spectral system, conversion from photon to electron and data gathering. The 355nm laser is used as light source because it has higher exciting efficiency and is safe to eyes. The receiver consists of telescope,coupling lens and fiber. The parameters of them are confirmed from theory calculate. The overlap of laser beam and telescope field of view is calculated when the flying height changes, in order to get the appropriate distance between laser and telescope. The spectral system is reconstructed from spectrometer. The grating efficiency and resolution are calculated to get the width of slit of fluorescence and Raman channel. The fluorescence and Raman channel use interferential filter to restrain the light in other wavelength and laser reflected from ocean surface. The photomultiplier tubes are used to converse photon to electron. The 40MHz A/D card realizes the data gathering. The software design consist of data gathering, database, performance simulation and data processing. The data gathering software gathers, saves and display the data from A/D card. The mechanical structure part introduce the position of lidar system on airplane and the mechanical structure of head of lidar and controlling cabinet. After airborne experiment, in order to overcome the shortages, it tables a proposal of 5 improvements for the system, include the upgrade of laser, the construct of new optics configuration, the selection of multichannel photomultiplier tubes, performance upgrade of A/D converter and the design of USB data acquiring with notebook computer adoption.The third part mainly introduces the software design with software engineering theory. It included the system analysis of ocean lidar, and designed the process of software. It designed a brand new lidar software, include data acquiring, storing, user interface and the estimation method of chlorophyll-a concentration.Some experiments are undertaken during building this system. They include the experiment of making sure the wavelength and bandwidth of fluorescence and Raman, the experiment of relationship between chlorophyll-a concentration and fluorescence intensity, the experiment of comparing fluorescence efficiency between 355nm and 532nm laser and the experiment of validating arithmetic that get the peak value of fluorescence and Raman, and the airborne experiment. The result of experiments shows that the relationship between chlorophyll-a concentration and fluorescence is near linear. The result of third experiment shows that 355nm laser have higher fluorescence efficiency than 532nm laser with same Nd:YAG laser which has same pulse energy at 1064nm. The success of experiment on flying validates the correctness of the design and adjustment of the airborne ocean lidar, and it provides valuable experience of the ameliorating of the system. It experiments many times after the experiment on flying.At the end of this dissertation all the content is summarized. At the same time the flaw of the system and way of improving is pointed out.