L. Mullen

Application of RADAR technology to aerial LIDAR systems for enhancement of shallow underwater target detection

Since microwaves do not penetrate water, RADAR, the principal tool for remote sensing of the earth and atmosphere, cannot be used directly for the detection of underwater objects. Currently, aerial light detecting and ranging (LIDAR) systems are therefore preferred for the detection and ranging of objects submerged in the sea. LIDAR provides for large area coverage at high speed, but it lacks coherent detection capability, a shortcoming that severely limits system sensitivity and underwater target contrast. In response to this problem, this paper details the merging of RADAR and LIDAR technologies in the constitution of a hybrid LIDAR-RADAR detection scheme. This new sensor configuration has reduced incoherent backscatter clutter by 17 dB in laboratory experiments and related computer simulations. >

Modulated pulse LIDAR system for shallow underwater target detection

This paper concerns the merging of the lightwave and microwave technologies in remote sensing and its application to airborne light detecting and ranging (LIDAR). By modulating an optical pulse at microwave frequencies, a coherent, underwater detection scheme is produced which provides orders of magnitude improvement over the presently-existing LIDAR system. Laboratory measurements show an unprecedented 17 dB optical (34 dB electrical) suppression of the backscatter clutter and a corresponding enhancement in shallow underwater target contrast. In this paper, the implementation of the modulated pulse LIDAR system is discussed and experimental results supporting the predicted improvements in detection sensitivity will be analyzed.<<ETX>>

Experimental and Theoretical Analysis of a Microwave-Modulated LIDAR System

This paper concerns the merging of the lightwave and miscrowave technologies for improvements in sensitivity and resolution of aerial light detecting and ranging (LIDAR) measurements. By the transposing of a microwave signal on a blue-green optical carrier, a hybrid LIDAR-RADAR detection scheme was created. Simulations and laboratory measurements showed a dramatic 17 dB optical (34 dB electrical) suppression of the backscatter clutter and corresponding improvement in contrast for shallow underwater targets.

Microwave-modulated transmitter design for hybrid LIDAR-RADAR

The application of well-established, coherent RADAR technology to aerial light detecting and ranging (LIDAR) systems has reduced incoherent backscatter clutter by 17 dB in laboratory experiments and computer simulations. The full-scale experimental realization of this hybrid LIDAR-RADAR system is hampered by the unavailability of a stable modulation source capable of providing high peak powers to overcome the large dynamic range required for the LIDAR backscatter measurement. Two methods being investigated for the microwave-modulation of a transmitted optical pulse to be utilized in the actual LIDAR environment are detailed.<<ETX>>

Ocean mass simulator for underwater LIDAR applications

Since microwaves are both reflected and absorbed by water, radar techniques cannot be utilized in the detection of underwater objects. For this situation, light detecting and ranging methods (LIDAR) are used. However, unlike radar, conventional LIDAR systems do not allow for coherent detection techniques which results in a loss in system sensitivity. Therefore, it is proposed that by combining millimeter wave and optical techniques, new coherent detection schemes can be developed. The transmitted optical signal in a LIDAR system is subject to attenuation, distributed backscattering, and dispersion as it propagates through the sea water. Since the goal of the project is to test hybrid microwave-LIDAR signal processing techniques, a simple, inexpensive method is needed to simulate the water medium. The backscattered signal from plastic optical fiber is examined to qualify the fiber as an accurate model of different types of sea water.<<ETX>>

Full scale hybrid lidar-radar system

This paper concerns a novel hybrid lidar-radar system for underwater surveillance. Simulations and laboratory measurements based on the hybrid detection scheme revealed a 17 dB suppression of the water backscatter signal (clutter) and corresponding target contrast enhancement. These results led to the design, implementation and testing of a full scale lidar-radar system. Details of this system and results obtained in the ocean experiment are presented.

Ocean LIDAR technology and applications

LIDAR (Light Detection And Ranging) systems have been developed for a wide range of oceanographic applications. This paper first reviews current LIDAR technology and applications. Technology advancements that will enhance the performance level of such systems for underwater investigation in the near future and make their use more economically feasible are then discussed. Transmitter, detector, and filter component improvements will refine the performance of existing systems as well as permit the implementation of new design approaches that take advantage of existing radar signal processing techniques.

Fabry-Perot intensity modulator for hybrid lidar-radar applications

To improve the detection sensitivity of aerial light detection and ranging (lidar), a hybrid lidar-radar detection scheme has been studied. Preliminary laboratory experiments are promising, but the full-scale realization of this novel system requires the development of high speed modulators for high power, blue-green laser pulses. This paper details experimental and analytical studies performed on a Fabry-Perot modulator suitable for lidar-radar applications.

Hybrid lidar-radar system for ocean experimentation

The merging of lidar and radar in the invention of a hybrid lidar-radar system has been shown to reduce incoherent backscatter clutter by 17 dB, with a corresponding enhancement of underwater target contrast. The success of these laboratory experiments led to the design of a system to be utilized in an ocean experiment. In the past, the main experimental restrictions in the full-scale realization have been the lack of a stable modulated transmitter and a large-area, high-speed optical receiver. Recent advances which have made these two components realizable for use in a hybrid system are detailed.

Evaluation of hybrid lidar-rader for ocean exploration

Past laboratory experiments established the ability of the hybrid lidar-radar system to improve underwater target contrast. Due to the limitations of the laboratory environment in assessing the performance of the hybrid detection scheme, a system was designed and constructed for use in an ocean experiment which was carried out in December, 1995. Results from the field test confirm the capability of hybrid lidar-radar to reduce backscatter clutter and enhance underwater target contrast. In addition, the existence of microwave subcarrier interference effects confirmed that the microwave signal integrity was maintained throughout the range of measurements.