Ines Leike

Experimental Validation of Wind Profiling Performed by the Airborne 10-μm Heterodyne Doppler Lidar WIND

The airborne Wind Infrared Doppler Lidar (WIND) has been developed through French‐German cooperation. The system is based on a pulsed 10.6-mm laser transmitter, a heterodyne receiver, and a conical scanning device. To the authors’ knowledge, it is the first airborne Doppler lidar for atmospheric research to retrieve the whole tropospheric wind profile between the ground and the flight level looking downward. The wind vector is measured with the velocity-azimuth display (VAD) technique with a vertical sampling of 250 m. The first flights on board the DLR Falcon 20 aircraft were performed in 1999. Results of a comparison among WIND, radiosondes, windprofiler radar measurements, numerical models, and simulations are presented. It is shown that the correspondence of airborne WIND measurements with those of other instruments or models is better than 1.5 m s21 and 58 for the horizontal wind vector. These results show the excellent capability of conical scanning Doppler lidars to provide unique insights into mesoscale dynamic processes and progress made toward future spaceborne systems.

Optimized additive mixing of colored light-emitting diode sources

Given a set of available LEDs or other light sources with known specifications including spectrum, total luminous flux (in lumens), and efficacy (in lumens per watts), we show how to select that combination which yields light of the desired (photometric) color and, in addition, maximizes various objectives such as efficacy, luminous flux, and color rendering index.

Mixing colored LED sources

Given a set of available LEDs or other light sources with known spectrum, total luminous flux (lumen) and efficacy (lumen/Watt), price etc. we show how to select that combination which yields light of desired (photometric) color and, in addition, maximizes efficacy, luminous flux , color rendering index or other objectives.

Visibility and Cloud Lidar

In summary it can be stated that visibility lidar is an accepted technology wherever impaired vision must be detected to impose speed limits to road or takeoff and landing restrictions to air traffic. Visibility lidars known as ceilometers have reached a degree of maturity to work 24 hours a day in the required fully-automated, hands-off operation mode. The development of much smaller systems for use under restricted space conditions and of systems small and cheap enough to be used as a truck and car accessory is in progress, with good chances to reach full commercial availability soon.

Virtual Doppler Lidar Instrument

Abstract Doppler lidars measure the range-resolved line-of-sight wind component by extracting the Doppler shift of radiation backscattered from atmospheric aerosols and molecules. A virtual instrument was developed to simulate wind measurements by flying virtually over the atmosphere. The atmosphere contains all components that influence the lidar, that is, wind, turbulence, aerosols, clouds, etc. For a selected time period, a dataset of the atmospheric conditions from the global model and the local model was provided by the German Weather Service. Three different Doppler lidar systems were simulated for this report: a coherent airborne conical scanning 10-μm Doppler lidar, a 10-μm and a 2-μm spaceborne system, and a spaceborne incoherent ultraviolet Doppler lidar.

ALIENS: atmospheric lidar end-to-end simulator

LabVIEW (National Instruments) provides a powerful instrumentation system for simulations, including an excellent graphical presentation environment. Our Doppler Lidar simulation tool contains signal propagation and scattering in the atmosphere, a model of the heterodyne front end in the low SNR-regime and a processing unit for signal digitizing and frequency estimation. As a consequence of LabVIEWs programming language, G, this end-to-end simulator for Laser Doppler wind measurement can run on either a Windows PC, a Macintosh PowerPC or a SUN station.

LabVIEW Software for Lidar Simulation

The use of coherent Doppler lidar for measuring atmospheric wind fields attracts considerable interest. A number of computer programs have been developed to simulate atmospheric return signals and extract wind speed information from it. We present a new software toolbox based on LabVIEW, differing from previous ones not only by a brilliant graphical user interface but also by stochastic return signal simulation, sophisticated heterodyne front end modelling and the choice among several frequency estimators.

Spaceborne Doppler lidar perspectives

Lidar technology and applications are well-established (Kirchbaumer et al. 1993). A backscatter lidar technology experiment was tested in space in 1994 (Winker et al. 1994). Scientists need global information on wind, clouds, and aerosol layers. On a space-borne platform, only a limited amount of power is available for a lidar system. Therefore, a compromise is necessary between the possibilities and the requirements.

New modules in the virtual backscatter lidar instrument

Since the presentation of the virtual backscatter lidar instrument in Firence, a lot of new modules have been added to the virtual instrument. A multiple hard target arrangement with selectable reflection parameters can be placed in a cloud or fog layer to simulate the collision avoidance problem. Further the complete atmospere with aerosols, molecules and clouds can be selected for airborne or spaceborne Doppler lidar simulations.

Multiple scattering effects demonstrated with the backscatter lidar virtual instrument (new version M)

We present a new software toolbox based on LabVIEW, that simulates the return signal of a backscatter lidar. The beam propagates through two different media: a layer, which is enclosed by two parallel planes and a surrounding medium. A large variety of environmental and instrumental conditions can be chosen for the calculation. Multiple scattering can be taken into account. This new version M contains a variety of new modules including a hard target which can be tilted to simulate the effect of pulse extension.