Linear FMCW Laser Radar for Precision Range and Vector Velocity Measurements
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Linear FMCW Laser Radar for Precision Range and Vector Velocity Measurements Diego F. Pierrottet1, Farzin Amzajerdian2, Larry Petway2, Bruce Barnes2, George Lockard2, and Manuel Rubio2 1 Coherent Applications, Inc., 101-C Research Drive, Hampton, VA, 23666 2 NASA Langley Research Center, MS 468, Hampton, VA, 23681 ABSTRACT An all fiber linear frequency modulated continuous wave (FMCW) coherent laser radar system is under development with a goal to aide NASA’s new Space Exploration initiative for manned and robotic missions to the Moon and Mars. 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. Linear FMCW lidar has the capability of high-resolution range measurements, and when configured into a multi-channel receiver system it has the capability of obtaining high precision horizontal and vertical velocity measurements. Precision range and vector velocity data are beneficial to navigating planetary landing pods to the preselected site and achieving autonomous, safe soft-landing. 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 measure directly the platform velocity by extracting the Doppler shift generated from the motion, as opposed to time of flight range finders where terrain features such as hills, cliffs, or slopes add error to the velocity measurement. Doppler measurements are about two orders of magnitude more accurate than the velocity estimates obtained by pulsed laser altimeters [4]. In addition, most of the components of the device are efficient and reliable commercial off-the-shelf fiber optic telecommunication components. This paper discusses the design and performance of a second-generation brassboard system under development at NASA Langley Research Center as part of the Autonomous Landing and Hazard Avoidance (ALHAT) project.
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 the Moon and Mars will become more focused towards landing at locations with high scientific value. This may include targeting sites near cliffs, valleys, craters, or other geographically interesting terrain [5,6]. Exploring technologies that will lead to an efficient and rugged method that provides feedback to the navigation and terrain hazard avoidance systems for soft landing at the targeted landing site are the main goals of this investigation [7]. This paper presents the work in progress of an all fiber lidar system capable
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