Dr. Faith J. February Profile

Dr. Faith J. February

at Univ of Cape Town

SPIE Involvement:

Author

Publications (14)

Proceedings Article | 16 November 2018 Paper

Investigation of aerosols in South Africa: Comparison of measurements and modeling

T. Kociok, F. February, P. Grossmann, D. Sprung, A. M. van Eijk, K. Stein

Proceedings Volume 10787, 1078704 (2018) https://doi.org/10.1117/12.2326526

KEYWORDS: Atmospheric modeling, Aerosols, MODIS, Data modeling, Atmospheric particles, Visibility, Satellites, Meteorology, Solids, Ocean optics

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Proceedings Article | 7 September 2017 Paper

In-situ and path-averaged measurements of aerosol optical properties

Sven van Binsbergen, Peter Grossmann, Faith February, Leo Cohen, Alexander M. van Eijk, Karin Stein

Proceedings Volume 10408, 104080V (2017) https://doi.org/10.1117/12.2275861

KEYWORDS: Aerosols, Atmospheric propagation, Atmospheric particles, Optical testing, Optical properties, Electro optics, Scattering, Absorption, Electro optical sensors, Electro optical systems

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Proceedings Article | 3 May 2017 Presentation + Paper

Improvements to the ShipIR/NTCS adaptive track gate algorithm and 3D flare particle model

Srinivasan Ramaswamy, David Vaitekunas, Willem Gunter, Faith February

Proceedings Volume 10178, 101780E (2017) https://doi.org/10.1117/12.2268673

KEYWORDS: Systems modeling, Thermal modeling, Missiles, 3D modeling, Particles, Infrared signatures, Image processing algorithms and systems, Detection and tracking algorithms, Image segmentation, Algorithm development, 3D acquisition

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Proceedings Article | 19 October 2016 Paper

FESTER: a propagation experiment, overview and first results

Christian Eisele, Dirk Peter Seiffer, Karin Stein, Erik Sucher, Willem Gunter, Faith February, George Vrahimis, Carl Wainman, Benita Maritz, Mokete Koago, Alexander M. van Eijk, Miranda van Iersel, Leo Cohen, Sven van Binsbergen, H. J. M. (Eric) Heemskerk, Armin Sternberg, Helmut Schulte, Arthur van Rheenen, Erik Brenthagen, Jan Thomassen, Derek Griffith

Proceedings Volume 10002, 1000208 (2016) https://doi.org/10.1117/12.2240771

KEYWORDS: Atmospheric propagation, Aerosols, Atmospheric particles, Sensors, Mid-IR, Long wavelength infrared, Environmental sensing, Turbulence, Halogens, Temperature metrology

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Proceedings Article | 19 October 2016 Paper

Path homogeneity along a horizontal line-of-sight path during the FESTER experiment: first results

W. Gunter, B. Maritz, M. Koago, C. Wainman, M. E. Gardener, F. February, A. M. J. van Eijk

Proceedings Volume 10002, 100020A (2016) https://doi.org/10.1117/12.2244531

KEYWORDS: Temperature metrology, Atmospheric propagation, Radio propagation, Water, Radiometry, Sensors, Long wavelength infrared, Skin, Electro optics, Black bodies

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Proceedings Article | 19 October 2016 Paper

Static and dynamic thermal infrared signatures measured during the FESTER experiment: first results

W. Gunter, F. February, D. Seiffer, C. Eisele

Proceedings Volume 10002, 100020C (2016) https://doi.org/10.1117/12.2244530

KEYWORDS: Infrared signatures, Temperature metrology, Infrared radiation, Sensors, Metals, Thermography, Environmental sensing, Mid-IR, Infrared sensors, Clouds

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Proceedings Article | 19 September 2016 Presentation + Paper

The FESTER field trial

Alexander M. van Eijk, Willie Gunter, Faith February, Benita Maritz, George Vrahimis, Mokete Koago, Carl Wainman, Christian Eisele, Dirk Seiffer, Erik Sucher, Karin Stein, Miranda van Iersel, Leo Cohen, Sven Van Binsbergen, H. J. M. (Eric) Heemskerk, A. Sternberg, H. Schulte, Arthur van Rheenen, Erik Brenthagen, Jan Thomassen, D. Griffith

Proceedings Volume 9979, 99790Q (2016) https://doi.org/10.1117/12.2240642

KEYWORDS: Electro optics, Environmental sensing, Long wavelength infrared, Turbulence, Sensors, Mid-IR, Atmospheric propagation, Aerosols, Temperature metrology, Metals

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Proceedings Article | 21 October 2014 Paper

Characteristics of turbulence driven atmospheric blur over coastal water

Arie de Jong, Piet B. Schwering, Koen Benoist, Willem Gunter, George Vrahimis, Faith October

Proceedings Volume 9242, 92421H (2014) https://doi.org/10.1117/12.2066192

KEYWORDS: Sensors, Modulation transfer functions, Scintillation, Data conversion, Turbulence, Cameras, Wavefronts, Water, Electro optical sensors, Refractive index

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For users of Electro-Optical (EO) sensors at sea, knowledge on their resolution is of key operational importance for the prediction of the obtainable classification ranges. Small targets may be located at ranges of 20 km and more and the present day sensor pixel size may be as small as 10 μrad. In this type of scenarios, sensor resolution will be limited by blur, generated by atmospheric turbulence, easily being greater than 30 μrad (at 20 km range). Predictions of the blur size are generally based upon the theory, developed by Fried [1]. In this theory, the turbulence strength is characterized by the structure parameter for the refractive index C_n ², of which data are assumed to be available from secondary instruments. The theory predicts the atmospheric Modulation Transfer Function (MTF), which can be incorporated into the total system MTF, used in range performance predictions, as described by Holst [2]. Validation of blur predictions by measurements is a complex effort due to the rapid variations of the blur with time and the problems associated with the simultaneous acquisition of proper C_n ² data. During the FATMOSE trial, carried out over a range of 15.7 km in the False Bay near Simon’s Town (South Africa) from November 2009 to October 2010, these data were collected in a large variety of atmospheric conditions [3]. In stead of the atmospheric MTF, the horizontal and vertical line spread function (LSF) was measured with a camera with 5 μrad resolution. Various methods for the determination of the LSF and the associated problems are discussed in the paper. The width of the LSF is via its Fourier transform directly related to the MTF. C_n ² data were collected with a standard BLS scintillometer over a nearby range. Additional C_n ²data were obtained via conversion of the scintillation data from the same camera and from a high speed transmissometer, collecting data over the same range. Comparisons between blur and Beam Wander predictions and measurements from the FATMOSE campaign are discussed in the paper as well as their impact on the range performance of present day sensors at sea.

Proceedings Article | 8 November 2012 Paper

Characteristics of long-range scintillation data over maritime coastal areas

Arie de Jong, Piet Schwering, Willem Gunter, George Vrahimis, Faith October

Proceedings Volume 8535, 853504 (2012) https://doi.org/10.1117/12.970566

KEYWORDS: Scintillation, Turbulence, Receivers, Sensors, Radiometry, Humidity, Data conversion, Imaging systems, Cameras, Atmospheric turbulence

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Proceedings Article | 18 May 2012 Paper

Long-term measurements of atmospheric point-spread functions over littoral waters as determined by atmospheric turbulence

Arie de Jong, Piet B. Schwering, Koen Benoist, Willem Gunter, George Vrahimis, Faith October

Proceedings Volume 8355, 83550M (2012) https://doi.org/10.1117/12.917718

KEYWORDS: Modulation transfer functions, Cameras, Scintillation, Turbulence, Sensors, Atmospheric turbulence, Spatial frequencies, Refraction, Visibility, Optical resolution

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Proceedings Article | 11 October 2011 Paper

Marine boundary layer investigations in the False Bay, supported by optical refraction and scintillation measurements

Arie de Jong, Alexander M. van Eijk, Koen Benoist, Willem Gunter, George Vrahimis, Faith October

Proceedings Volume 8178, 817808 (2011) https://doi.org/10.1117/12.897461

KEYWORDS: Dysprosium, Refraction, Ocean optics, Scintillation, Data modeling, Humidity, Temperature metrology, Atmospheric modeling, Water, Turbulence

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Proceedings Article | 7 September 2011 Paper

Application of year-round atmospheric transmission data, collected with the MSRT multiband transmissometer during the FATMOSE trial in the False Bay area

Arie de Jong, Alexander van Eijk, Leo Cohen, Peter Fritz, Willem Gunter, George Vrahimis, Faith October

Proceedings Volume 8161, 81610A (2011) https://doi.org/10.1117/12.892023

KEYWORDS: Humidity, Visibility, Aerosols, Atmospheric modeling, Atmospheric particles, Atmospheric propagation, Atmospheric optics, Particles, Atmospheric sensing, Sensors

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The FATMOSE trial (False Bay Atmospheric Experiment) is a continuation of the cooperative work between TNO and IMT on atmospheric propagation and point target detection and identification in a maritime environment (South Africa). The atmospheric transmission, being of major importance for target detection, was measured with the MSRT multiband optical/IR transmissometer over a path of 15.7 km over sea. Simultaneously a set of instruments was installed on a midpath lighthouse for collection of local meteorological data, including turbulence, scintillation, sea surface temperature and visibility. The multiband transmission data allow the retrieval of the size distribution (PSD) of the particles (aerosols) in the transmission path. The retrieved PSD's can be correlated with the weather data such as windspeed, wind direction, relative humidity and visibility. This knowledge will lead to better atmospheric propagation models. The measurement period covered nearly a full year, starting in November 2009 and ending in October 2010. The False Bay site is ideal for studies on propagation effects over sea because of the large variety of weather conditions, including high windspeed, expected from the South East with maritime air masses, as well as Northerly winds, expected to bring warm and dry air from the continent. From an operational point of view the False Bay area is interesting, being representative for the scenery around the African coast with warships in an active protecting role in the battle against piracy. The yearround transmission data are an important input for range performance calculations of electro-optical sensors against maritime targets. The data support the choice of the proper spectral band and contain statistical information about the detection ranges to be expected. In this paper details on the instrumentation will be explained as well as the methods of calibration and PSD retrieval. Data are presented for various weather conditions, showing correlations between different parameters and including statistical behaviour over the year. Examples will be shown of special conditions such as refractive gain, gravity waves and showers.

Proceedings Article | 12 October 2010 Paper

Preliminary results of the FATMOSE atmospheric propagation trials in the False Bay, South Africa, November 2009-July 2010

Arie de Jong, Peter Fritz, Koen Benoist, Alexander van Eijk, Piet Schwering, Willem Gunter, George Vrahimis, Faith October

Proceedings Volume 7828, 782809 (2010) https://doi.org/10.1117/12.864067

KEYWORDS: Visibility, Scintillation, Atmospheric propagation, Data modeling, Cameras, Sensors, Atmospheric modeling, Refraction, Aerosols, Imaging systems

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The FATMOSE trial (FAlse-bay ATMOSpheric Experiment) running over a period from November 2009 to July 2010, was a continuation of the cooperation between TNO and IMT on atmospheric propagation and point target detection and identification in a maritime environment. Instruments were installed for measuring scintillation, blurring- and refraction effects over a 15.7 km path over sea. Simultaneously, a set of instruments was installed on a mid-path lighthouse for collecting local meteorological data, including scintillation, sea surface temperature and visibility. The measurements covered summer and winter conditions with a prevailing high wind speed from the South East, bringing in maritime air masses. The weather conditions included variations in the Air-Sea Temperature Difference (ASTD), that may affect the vertical temperature gradient in the atmospheric boundary layer, causing refraction effects in the lightpath. This was measured with a theodolite camera, providing absolute Angles of Arrival (AOA). Blur data were collected with a high resolution camera system with 10 bits dynamic range. Specially designed image analysis software allows determination of the atmospheric blur, while simultaneously providing information on the Scintillation Index (S.I.). This S.I. was also measured by using the Multiband Spectral Radiometer Transmissometer (MSRT). The ratio of the transmission levels of this instrument contains information on the size distribution of the aerosols along the path. In the paper, experimental details on the set-up and the instrumentation are given as well as the methods of analysis. Preliminary results are shown, including a comparison of measured blur and scintillation data with Cn 2 data from the scintillometer, correlation between AOA and ASTD and comparison of transmission data with data from the visibility meter. Blur and scintillation data are compared with predictions from standard turbulence model predictions, using Cn 2. In future studies the data will be used for validation of propagation models such as EOSTAR.

Proceedings Article | 7 November 2007 Paper

Optical characterization of small surface targets

Piet Schwering, Dirk Bezuidenhout, Willem Gunter, Arie de Jong, Peter Fritz, Francois le Roux, Rheinhardt Sieberhagen, Mark Holloway, George Vrahimis, Faith October, Rob Kemp

Proceedings Volume 6739, 67390H (2007) https://doi.org/10.1117/12.738507

KEYWORDS: Sun, Scintillation, Mid-IR, Sensors, Long wavelength infrared, Signal to noise ratio, Target detection, Imaging systems, Electro optical systems, Refraction

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Showing 5 of 14 publications

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