The success of interferometry in space depends on the development of lasers that can survive launch conditions and the challenging space environment during missions that could last five years or more. This paper describes the fabrication of a rugged, laser-welded package for a 200mW, monolithic diode-pumped solid-state Nd:YAG laser operating at 1319nm. Environmental testing shows that the laser withstands non-operational thermal cycles over a temperature range from -20°C to 55°C, and 22.3 g-rms of random vibration, with little or no degradation of laser output power or performance. The novel packaging method employs a specially designed housing to which multi-mode or single-mode polarization-maintaining fiber pigtails can be aligned and laser-welded into place. To further enhance reliability, a redundant pumping system called the Multi-Fiber Pump Ferrule (MFPF) was developed and implemented. The MFPF allows multiple laser diode pump modules to be aligned to the laser crystal simultaneously, in order to accommodate either parallel or standby pump redundancy. This compact, lightweight design is well suited for space flight applications and the laser-welded technique can easily be adapted to a number of other fiber optic and electro-optic devices in which critical optical alignments must be maintained in a harsh environment.
KEYWORDS: LIDAR, Signal processing, Wind measurement, Digital signal processing, Velocity measurements, Control systems, Sensors, Atmospheric optics, Oscillators, Transceivers
NASA and the FAA have expressed interest in laser radar's capabilities to detect wind profiles at altitude. A number of programs have been addressing the technical feasibility and utility of laser radar atmospheric backscatter data to determine wind profiles and wind hazards for aircraft guidance and navigation. In addition, the U.S. Air Force is investigating the use of airborne lidar to achieve precision air drop capability, and to increase the accuracy of the AC- 130 gunship and the B-52 bomber by measuring the wind field from the aircraft to the ground. There are emerging capabilities of airborne laser radar to measure wind velocities and detect turbulence and other atmospheric disturbances out in front of an aircraft in real time. The measurement of these parameters can significantly increase fuel efficiency, flight safety, airframe lifetime, and terminal area capacity for new and existing aircraft. This is achieved through wind velocity detection, turbulence avoidance, active control utilization to alleviate gust loading, and detection of wingtip wake vortices produced by landing aircraft. This paper presents the first flight test results of an all solid-state 2-micrometers laser radar system measuring the wind field profile 1 to 2 km in front of an aircraft in real time. We find 0.7-m/s wind measurement accuracy for the system which is configured in a rugged, light weight, high- performance ARINC package.
A model dust distribution over the lunar terminator region, based on instrument measurements and observations by Apollo astronauts, is used to assess the feasibility of detecting and mapping the dust distribution with a lunar-based lidar instrument. We assume a refractive index appropriate to volcanic dust, and use Mie scattering formalism along with the model dust distribution to determine the expected lidar backscatter coefficient as a function of range cell location. Requirements for peak transmitter power, pulse length, and pulse repetition rate are examined. This analysis is carried out both for a lunar surface instrument package and for a lunar orbiting instrument. Orbital instrument requirements are analyzed for orbital altitudes of 60, 80, and 100 km above the lunar surface. Expected signal-to-noise ratios and additional performance parameters are presented for these candidate lidar systems. Size and power requirements for the instruments are also discussed.
The paper describes the design and performance of the Coherent Launch Site Atmospheric Wind Sounder (CLAWS), which is a test and demonstration program designed for monitoring winds with a solid-state lidar in real time for the launch site vehicle guidance and control application. Analyses were conducted to trade off CO2 (9.11- and 10.6-microns), Ho:YAG (2.09 microns), and Nd:YAG (1.06-micron) laser-based lidars. The measurements set a new altitude record (26 km) for coherent wind measurements in the stratosphere.
The problems of obtaining and processing information in pulsed laser rangefinders in order to determine ranging object characteristic feature selection and identification under permanent echo conditions are considered, including the influence of target spatial length, radiation beam nonuniformity, and random rangefinder target guidance error. Automatic target selection algorithms and circuits are also considered. The principle of target signal selection and identification based on reflected pulse data is proposed.
KEYWORDS: LIDAR, Sensors, Navigation systems, Signal processing, Backscatter, Nd:YAG lasers, Carbon dioxide, Wind measurement, Aerosols, Signal to noise ratio
The coherent launch-site atmospheric wind sounder (CLAWS) is a lidar atmospheric wind sensor designed to measure the winds aloft at space launch facilities to an altitude of 20 km. Candidate lidar systems analyzed for use in CLAWS include Nd:YAG, Ho:YAG, and CO2. Detailed simulations were carried out by Coherent Technologies, Inc. The results of our development studies include: (1) definition of lidar sensor requirements, (2) definition of a system to meet those requirements, and (3) a concept evaluation with recommendations for the most feasible and cost-effective lidar system for use as an input to a guidance and control system for a missile or spacecraft launch. A field test program will begin in August 1991, in which the ability of CLAWS to meet NASA goals for increased safety and launch/mission flexibility at Kennedy Space Center (KSC) will be evaluated with regard to maximum detection range, refractive turbulence, and aerosol backscattering efficiency at the three lidar wavelengths. It is found that the shorter wavelength solid-state lasers will afford better performance (longer detection range), are more energy efficient, and are more compact for operation in the humid, postvolcanic aerosol environment found at KSC. Finally, the Ho:YAG (2.1 micrometers ) lidar gives the best performance at an eyesafe wavelength and would be applicable for detecting winds aloft during descent as well as during ascent.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.