This paper relates a short history of laser radar development in the United States. It starts in the 60's, shortly after
the invention of the laser. Initially laser radars used various lasers, until CO2 became the popular choice for coherent
laser radar and NdYag for laser range finders and designators. CO2 reigned as the coherent laser radar of choice
from the early 70's until the 80's or 90's. Most CO2 laser radars were at a wavelength of 10.6 μm, although to
avoid atmospheric CO2 absorption some CO2 laser radars used different isotopes of CO2 to avoid 10.6 μm
operation. The exception to the early laser radar development being CO2 were laser designators, which can be
considered a form of bi-static laser radar, and laser range finders. NdYag, at 1.064 μm wavelength, was the laser of
choice for laser designators and range finders. Laser designators started in the late 60's. In the 80's to 90's solid
state lasers came more into their own for laser radar application, including coherent solid state laser radars. The
main development was the ability to eliminate heat from solid state material, thus allowing higher power operation.
Laser diodes also became prominent, allowing a reliable and efficient method of pumping. Wind sensing,
navigation, terrain following, 2D, and 3D imaging, and velocity detection are some of the other laser radar uses that
have been pursued. CO2 based navigation laser radar was deployed, but with the advent of GPS has become less
This paper discusses the design and development of a 2J, 10Hz coherent Doppler wind lidar transmitter for global wind sensing from the International Space Station. This work is being performed in support of a proposal to operate such a lidar from the Japanese Experimental Module. The conceptual lidar transmitter design is complete and risk reduction measurements are currently underway to demonstrate the 2J, 10Hz operation using a 2 micron laser transmitter with a MOPA (master oscillator – power amplifier) configuration. The paper discusses the lidar performance requirements for global wind sensing from the Space Station, general design characteristics of the two micron lidar transmitter, and the current status of the risk reduction measurements.
KEYWORDS: Human-machine interfaces, Transceivers, LIDAR, Laser development, Solid state lasers, Signal processing, Solid state physics, Solid state electronics, Wind measurement, Laser systems engineering
Diode-pumped solid-state pulsed coherent laser radar systems have recently been developed at Coherent Technologies, Inc., for the remote measurement of atmospheric wind fields. Flash- lamp pumped systems have been utilized since 1990 for obtaining wind field measurements. These flash-lamp pumped lidar systems have been applied to wind profiling, aircraft wake vortex measurements, airport wind shear and gust front monitoring, and military cargo air drops and many other applications. The diode-pumped coherent lidar systems currently available are capable of near turnkey operation. The Tm:YAG laser transceivers operate at 2.02 microns with output pulse energies of 1 t 10 mJ with PRFs of 1,000 to 100 Hz respectively. Range resolution of 30 - 75 m are typical. A real-time lidar signal processor has also been developed for collecting and analyzing laser radar (lidar) data. The signal processor is based on a commercial PC architecture and offers a real-time data acquisition, analysis, display, recording and playback environment. Wind measurements and overall system performance results are presented. Wind measurement performance, for a variety of applications, are presented using the flashlamp and diode pumped coherent lidars including measured wind profiles from ground and on aircraft, wake vortex tracking results, and example flows over mountain terrain.
Pulsed coherent solid-state 2 micron laser radar systems have been developed at Coherent Technologies, Inc. for ground- and airborne-based applications. Ground-based measurements of wind profiles and aerosol backscatter have been performed for several years. Examples of wind and aerosol backscatter coefficient measurements will be presented which cover a variety of weather conditions. Airborne measurements of wind profiles below the aircraft have been performed by Wright Laboratories, operating in a VAD measurement mode and will be reviewed. An engineered flight-worthy coherent lidar system is under development at CTI for flight on the SR-71 aircraft, in support of the High Speed Civil Transport program. Flights will be conducted by NASA-Dryden Flight Research Center at altitudes above 60,000 feet for the measurement of atmospheric turbulence ahead of the aircraft. Efforts are also underway at CTI for the development of high power coherent laser radar systems. Extensive detailed physical optics models of diode-pumped solid-state laser performance have been developed to characterize transient thermo-optic aberrations and the overall efficiency of lasers intended for space-based applications. We are currently developing a 2 micron 0.5 J/pulse transmitter with a 10 Hz PRF and a pulse duration of 400 - 500 ns. The status and expected space-based wind measuring performance for this system will be presented.
Coherent lidar systems based on eyesafe solid-state laser technology are rapidly emerging in ruggedized packages. The airport terminal area presents several measurement scenarios appropriate for application of pulsed coherent lidar sensors. This paper briefly reviews the status of coherent lidar technology and presents results produced with a mobile flashlamp- pumped 2.09 micrometers coherent lidar sensor for windshear detection and measurement, wind turbulence estimation, and wake vortex detection and tracking.
A low average power, pulsed, solid-state, 1.06-micron coherent laser radar (CLR) for range and velocity measurements of atmospheric and hard targets has been developed. The system has been operating at a field test site near Boulder, CO since September, 1988. Measurements have been taken on moving targets such as atmospheric aerosol particles, belt sanders, spinning disks, and various stationary targets. The field measurements have shown that this system exhibits excellent velocity measurement performance. A fast-tuning CW Nd:YAG oscillator has also been developed which has a frequency tuning range of greater than 30 GHz (which spans a target radial velocity range of over 16 km/s) and a tuning speed greater than 30 GHz/ms.