Arecibo Observatory Lidar Capabilities
Potassium Doppler-Resonance Lidar
- The transmitter is a pulsed Alexandrite Ring
Laser injection seeded by an external cavity Diode Laser. The
diode laser is locked to the central cross-over feature of the
Doppler-free spectrum from the K D1 spectral
- The diode laser is frequency modulated by a
dual-pass acousto- optic modulation setup developed by the
lidar group at
Colorado State University in order to get the spectral
information necessary to measure potassium temperature in the
- The receiver consists of an 800 mm diameter
Cassegrain telescope that is fiber-optically coupled to
receiver optics made up of an optical chopper to block
low-altitude return, a narrow-band interference filter to
reduce background, and an electronically gated GaAs
Multi-metal Resonance Lidar
- This lidar uses a pulsed dye laser pumped by a
Nd:YAG laser for its transmitter. The fundamental output can
operate in the yellow to near-IR in order to measure Na or K
densities. This output can be doubled or mixed with residual
IR from the Nd:YAG laser at 1064 nm in order to reach wavelengths
for Fe, Ca, Ca+, or for DIAL studies of O3
near 310 nm.
- The laser output is wavelength locked using a
pulsed wavemeter and software developed at the Arecibo
Observatory in order to feed back to the dye laser's rotating
- As with the K lidar, the receiver consists of
an 800 mm diameter Cassegrain telescope that is fiber-optically
coupled to receiver optics made up of an optical chopper to block
low-altitude return, a narrow-band interference filter to reduce
background, and an electronically gated GaAs photomultiplier
Doppler Rayleigh-Mie Lidar
- The Rayleigh-Mie transmitter is an injection-
seeded pulsed Nd:YAG laser. The PRF is 40 Hz, and the average
power is 24 W. The seed laser is frequency locked to the edge of
an absorption line in I2.
- The receiver is the same as above, except that,
after exiting the fiber, the received light is split into two
channels. The first goes directly to a photomultiplier, while
the second passes through an I2 vapor cell before being
detected by a PMT.
- The ratio of filtered to unfiltered signal gives
frequency information for measuring the winds. A Doppler shift
is seen as an increase or decrease in absorption by the I2.
Temperature profiles are gleaned from the unfiltered channel.
This system works for altitudes above 20 km where the Mie
scattering component of the signal is negligible. See our
publications list for a
reference to a more complete description of this system.
Arecibo Observatory Lidar Projects
Doppler Resonance Lidar
- Mesopause Climatology: Long-term seasonal studies
of the climatology of the mesopause. This study is presently
underway with nighttime temperature profiling between 85 and 100 km.
At a later date we will add line-of-sight winds and, using an ultra-
narrow-band filter to cut out the solar background, daytime
- Dynamics and Chemistry of Atomic Layer Enhancements:
The study of neutral atomic layer enhancements, sometimes called
"sporadic" or "sudden" layers. Doppler measurements will make
temperature profiles of the layers and look for wind shears or other
dynamics which may lead to their formation. Working in combination
with the multi-metals lidar (see below), we can also gain clues to
the chemical reactions taking place within the layers.
- Tides and Gravity Waves: Short-term (during one or
several consecutive nights) observations of the temperature (and
wind) structure of the mesopause gives valuable information on the
gravity wave spectrum, wave-breaking, and tidal motions.
Multi-Metal Resonance Lidar
- Meteor Composition Studies: Meteors burn up in the
upper atmosphere, between 80 and 120 km, leaving behind a trail of
ions, atoms, molecules, and dust. Using resonance lidar, the
increase in the quantity of a given atomic species due to a meteor
can be detected. By observing two or more metals, some idea of
meteor composition and ablation sequence can be determined.
- Simultaneous observation of a metal and its ion:
By switching between wavelengths, near-simultaneous observations of
Ca and Ca+ can be made. This is especially useful to
the study of layer chemistry and the formation of atomic layer
- Stratospheric and Mesospheric Climatology, Waves,
and Tides: The Rayleigh lidar can profile atmospheric
temperatures in the altitude range from 30 to 80 km. It can
also profile winds to above 50 km. This makes it a powerful
instrument in the study of middle atmospheric dynamics.
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