A turnkey lidar system with
depolarization sensitivity.
A turnkey lidar system with
depolarization sensitivity.
Brief System Description
PEELS was developed by Visidyne to address those issues
which have restricted the routine use of conventional lidar technology.
The state-of-the-art components employed in PEELS as well as its system
design and rigid construction allow for safe, sensitive, reliable, unattended,
and continuous operation. In addition, it is small, robust, easily
transportable, and readily configurable for different basing modes.
The system operates at a wavelength of 1.574 microns using a compact laser/OPO
transmitter. The receiver delivers unsurpassed performance by employing
proprietary F/1 optics and the most sensitive proven detector technology
available for this wavelength. The baseline system incorporates dual
channel polarization sensitive reception in order to quantify both the magnitude
and depolarization characteristics of the target
backscatter. Several models of PEELS have been built and extensively
utilized by customers in both ground and aircraft based configurations.
The applications have included tracking, mapping, and depolarization discrimination
of: rocket effluents, anthropogenic dust clouds, hard targets, and
optically thin to subvisual cirrus clouds.
Sample Data: Ground Based, Signal Averaging Mode
The images below illustrate 90 minutes of ground based
PEELS data accumulated at a 31 degree elevation angle, on a clear cool
New England fall day, and with an averaging time of about 1 minute.
The lower troposphere aerosol layering evident in the data was not visually
discernible. The cirrus cloud coverage was visually discernible but
optically quite thin. The data also clearly show that the
cirrus cloud backscatter depolarization was in the expected range for (irregular)
ice particles (0.3-0.7), whereas the depolarization of the lower layer
is consistent with (near spherical) liquid aqueous aerosols (0.01-0.04)
with, perhaps, a dust component (0.06-0.1).
Sample Data: Aircraft Based, Single Shot Mode
The images below are representations of about 1 minute
of single shot data from an aircraft-configured PEELS. The PEELS
unit was mounted in FISTA (a USAF AFRL research aircraft) and directed
15 degrees from the nadir with a mirror assembly. During this short
sequence of data the aircraft was flying at about 9.1 km AGL (10.4 km MSL)
over open high desert. Two narrow but distinct cloud layers are evident
between about 4 and 5 km AGL. The depolarization ratio clearly shows
the first cloud layer to be almost entirely a liquid water cloud, whereas
the second and slightly lower layer is either a pure or partial ice cloud.
Additional analysis of the ground return (at the bottom of the images)
further confirms this by showing that the backscatter-to-extinction ratio
of the first layer is about 4 times greater than that of the second layer.
Baseline System Features