REMTECH Inc. Sonar Brochure Page

Long - Range Currentmeter Sonar

Complete Sonar System (emission/reception transducer and electronics)

It is a vessel-mounted system consisting of a single 52-element emission/reception transducer with electronic beam steering to allow for measurement along 5 axes, and a cable to the signal- processing electronics. The computer performs calculations similar to those performed by our Doppler Sodars, which use acoustic waves for remote measurement of wind. A recent round of testing has shown that depths beyond 1000 meters can be reached given one- minute averaging periods on a boat moving at a speed of five knots.

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REMTECH Inc. Sonar Brochure Page

Real-Time display of echo and current velocity relative to ship during a short transect in the Mediterranean sea. The ship was moving about 3 knots for the first period, and at about 4.5 knots in the second period. Range was limited due to water depth

Copyright(c) 1997-2007 Remtech Inc. Updated: 11/2007

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REMTECH Inc. Rass Brochure Page

The smallest and most accurateradio-acoustic wind and temperature profiler

in the world

PA2 Antenna between the R.A.S.S. antennas

A FAMILY ATMOSPHERE

Meteorologists, atmospheric physicists, civil and military airport directors, communication engineers, and safety teams at sites subject to major technological risks (nuclear power plants, highly polluting chemical complexes, ...) may now breathe easier. Thanks to the REMTECH DOPPLER SODAR, these groups already have accurate measurements of horizontal wind speed and direction as well as vertical wind speed and turbulence in the lower layers of the atmosphere.

But, in order to forecast the complex behaviour of air masses, essential data such as the temperature of the different layers of air was missing. Alternatives such as radio sondes or tethered balloons, being costly in time and material, could surely not fulfill the needs for real-

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time continuous vertical temperature profiles.

REMTECH now fills in this gap with the development of the RASS, or Radio Acoustic Sounding System, for accurate measurements of remote temperature.

An important complement to the SODAR, the RASS radar takes advantage of the combination of two technologies, acoustic and electromagnetic, to provide a real time temperature profile and deduce from it, with good temporal resolution, the "strength" of the temperature gradient. For risk assessment applications, a RASS together with a SODAR makes it easy to measure inversion phenomena responsible for trapping pollutants and storing them in the elevated layers of the first two thousand meters of the atmosphere.

The RASS also provides essential data for the improvement in models for real time fog forecasting at airports.

The RASS is a unique tool for civil and military telecommunications. It can detect if an inversion is present, how "strong" this inversion is, and therefore, better understand, and then control, the aberrations related to the propagation of radio waves. With RASS data, the real time optimization of transmitting frequency and antenna orientation is possible.

As for future developments, one can easily imagine the amount of information a RASS could provide to the operation of high power lasers.

Yes, with the RASS, the atmosphere will look more and more familiar.

A Leading Technique

The RASS applies a simple principle of physics: the

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REMTECH Inc. Rass Brochure Page

relationship of the speed of sound and air temperature. A RASS processes a small part of the energy from a continuous radio wave backscattered by the inhomogeneities in the atmosphere caused by an acoustic pulse transmitted from the vertical antenna of the SODAR. Doppler processing of the signal received by a second radar antenna makes it possible to measure the speed of the vertically moving "target", here the acoustic wave train, and extract from it the air temperature. However it required the expertise of REMTECH engineers in the field of micrometeorology to transform this simple principle of physics into an accurate and reliable system such as the RASS. The system can operate even with high horizontal winds where the acoustic waves have drifted away from the antennas.

Antennas

The numerical models and manufacturing techniques, which were successfully developed over many years for the SODAR, have been applied to the RASS antennas. Secondary lobes are considerably reduced, resulting in small scale antennas. These can be easily transported from one site to another on a trailer.

A Convenient Compliment

From its inception, the SODAR electronic case was designed to accept the input of an extra signal. Thanks to this design, every REMTECH

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REMTECH Inc. Rass Brochure Page

SODAR ,manufactured to date can accept a RASS radar; antennas, amplifiers, filters and mixer. A new RASS software takes care of extracting the necessary information to provide profiles both of wind and temperature.

Signal Processing

The above block diagram illustrates the RASS signal processing: after mixing the received radio frequency and the transmitted frequency, the frequency of the signal is of the same order of magnitude as the acoustic frequency transmitted by the SODAR antenna. This "audio" signal can therefore be processed (filtering, amplification, Fast Fourier Transform, "doppler" software) in the identifical manner utilizing the standard SODAR computer.

The RASS thus takes advantage of the expertise gained over the years by REMTECH with software processing of noisy and very low amplitude signals. It also profits from the accuracy of the three-dimensional SODAR taking into account the influence of horizontal and vertical wind speeds on the received radar frequency.

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REMTECH Inc. Rass Brochure Page

Comparison between RASS and B.A.O. tower data

(Boulder Atmospheric Observatory, CO)

The RASS: A new understanding of the air

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Unlimited Applications

Don't stay in the fog any more! The RASS brings useful answers to problems previously without solutions, such as: - the forecast, in real time and with a good accuracy, of the onset of fog at airports, thanks to continuous temperature profiles, - the control of aberrations in radio wave propagation due to temperature inversions which disturb radio links and radar coverage, - the optimal use of high power lasers.

The RASS also complements the SODAR in its classical applications: - the improvement of risk assessment models at sites which involve major technological risks (nuclear power plants, chemical

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industries, urban pollution alert networks, ...), - the development of complex terrain models for which continuous temperature profiles are necessary, - the better understanding of noise propagation (aircraft noise certification, ...).

Copyright(c) 1997-2007 Remtech Inc. Updated: 11/2007

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REMTECH Inc. Sodar Brochure Page

Phased Array Sodar Familyfor all Ranges and Applications

The Main Sail.....and the Computer

Among the four elements, air is by far the least understood. A major concern for sailing and trade in the old days ( trade winds ), the study of wind

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fell into neglect when steam power appeared.

Nuclear power plant and industrial site monitoring, airport safety requirements and intensive agriculture have created an urgent need for the study of air masses . Totally accurate and reliable instrumentation was needed which could operate continuously in order to assess statistical and climatological models and which could also be used in real time.

After years of intensive research in cooperation with various governments and military agencies in both Europe and in the U.S. , REMTECH is especially proud of its third generation DOPPLER SODAR.

Universally acknowledged, it is the most versatile system for measuring wind, wind turbulence and the temperature structure in the planetary boundary layer. It is what the scientific community has been waiting for.

A Leading Technique

The

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REMTECH Inc. Sodar Brochure Page

REMTECH DOPPLER SODAR processes the echo of an acoustic pulse which is directed into the atmosphere. The frequency shift of the echo varies according to the wind speed (this is the DOPPLER effect ) while the echo intensity varies according to thermal turbulence and structure. Each REMTECH DOPPLER SODAR uses a single, multicellular antenna whose beam is steered electronically. The basic antenna is composed of 52 elements, is only 40 cm x 40 cm x 15 cm in size, and weighs, with its electronics and computer, less than 20 kg, which makes it the first portable Sodar in the world. Despite its size, however, it is capable of measuring up to 600 m and beyond. By using more powerful acoustic emitters, larger dimensions and lower acoustic frequencies, we are able to reach altitudes of up to 5,000 meters.

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REMTECH Inc. Sodar Brochure Page

A FULLY DIGITAL DATA PROCESSING

A Fast Fourier Transform application has been chosen by REMTECH to process the received signal. The system's hardware is simply comprised of a personal computer, a transceiver board and power amplifiers, all of which is mounted in an electronics case.

STAND ALONE OPERATION

The REMTECH DOPPLER SODAR is presently the only Sodar which outputs real-time data of guaranteed precision without any human intervention. This is made possible primarily by a pulse-coding technique and a fixed echo detection subroutine.

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REMTECH Inc. Sodar Brochure Page

A COMPLETE RANGE OF INSTRUMENTS AND SYSTEMS

In order to respond to the various requests of our clients, REMTECH has developed a whole family of DOPPLER SODARS. It ranges from the portable PA0 model, which weighs around 20 kg, to tropospheric profilers such as the PA5, whose antenna measures 1.8 m x 1.8 m and whose range reaches as high as 5,000 meters. Numerous other options are available, such as software for climatological and rnicrometeorological applications.

REMOTE DIAGNOSTICS

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Due to the software-oriented policy REMTECH has adopted which has allowed the systems' hardware to be reduced to a minimum, it is possible to monitor the Sodar via a simple modem link.

MULTIPLE APPLICATIONS

The applications for the REMTECH DOPPLER SODAR are numerous. Some examples include - environmental impact studies - elevated stable layer characterization - prediction of the consequences of nuclear accidents or toxic chemical spills - consideration of wind fields in studies of the trajectory of flying objects - quantifying the effects of atmospheric turbulence on the propagation of light and radio waves - airport measurement of windshear and radio wake turbulence created by large airplanes - wind energy siting - etc...

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PA1 Antenna

PA2 Antenna between the R.A.S.S. antennas(RASS is an option for remote measurement of air temperature)

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Copyright(c) 1997-2008 Remtech Inc. Updated: 12/2008

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