Development of an All-Fiber Coherent Laser Radar for Precision Range and Velocity Measurements
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Development of an All-Fiber Coherent Laser Radar for Precision Range and Velocity Measurements Diego Pierrotteta, Farzin Amzajerdianb, and Frank Perib a Coherent Applications, Inc., Hampton VA, 23669 b NASA Langley Research Center, Hampton VA 23681 ABSTRACT An all-fiber coherent laser radar system capable of high-resolution range and line of sight velocity measurements is under development with a goal to aid NASA’s new Space Exploration initiative for manned and robotic missions to the Moon and Mars. Precision range and velocity data are key parameters to navigating planetary landing pods to the pre-selected site and achieving autonomous safe soft-landing. By employing a combination of optical heterodyne and linear frequency modulation techniques [1-3] and utilizing state-of-the-art fiber optic technologies, highly efficient, compact and reliable laser radar suitable for operation in a space environment is being developed. The all-fiber coherent laser radar has several important advantages over more conventional pulsed laser altimeters or range finders. One of the advantages of the coherent laser radar is its ability to directly measure the platform velocity by extracting the Doppler shift generated by the platform motion. The Doppler velocity measurement is about two orders of magnitude more accurate than the velocity estimates obtained by laser altimeters using the rate of change in range [4]. Another advantage is continuous-wave operation that allows the use of highly efficient and reliable commercial off-the-shelf fiber optic telecommunication components. This paper will describe the design and operation of this laser radar sensor and discuss its projected performance. A laboratory breadboard system has already been developed as a step toward a flight prototype. The experimental data representing the potentials of this laser radar system will be reported. INTRODUCTION The motivation behind the development of an all-fiber high resolution coherent lidar system comes from the need to meet requirements set by NASA’s space exploration initiative. To support activities related to planetary exploration missions, this effort addresses the call for advancement of entry, descent, and landing technologies. Future exploratory missions to Mars will become more focused towards landing at locations with high scientific value. This may include targeting sites near cliffs, valleys or other geographically interesting terrain [5,6]. Exploring technologies that will lead to an efficient and rugged method of acquiring and locking into a target landing site by supplying feedback to the navigation and terrain hazard avoidance systems are the main goals of this investigation [7]. This paper presents the work in progress of an all fiber lidar system capable of providing critical descent range and velocity of the planetary vehicles with a high degree of precision. The development of a breadboard system is reported and the experimental data characterizing its operation is described.
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LASER WAVEFORM DESCRIPTION The lidar
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