Dr. Eric H. J. Heemskerk Profile

Dr. Eric H. J. Heemskerk

at TNO-FEL

SPIE Involvement:

Author

Publications (4)

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 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 | 14 October 2005 Paper

Comparison of atmospheric refraction at radar and optical wavelengths

Gerard Kunz, Eric Heemskerk, Lex van Eijk

Proceedings Volume 5981, 59810B (2005) https://doi.org/10.1117/12.638613

KEYWORDS: Refraction, Humidity, Atmospheric propagation, Atmospheric modeling, Meteorology, Infrared radiation, Water, Refractive index, Atmospheric optics, Sensors

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A study is carried out to classify possible combinations of refractivity conditions for RF and IR over a wide range of meteorological conditions using different micrometeorological bulk models. The calculated refractivity profiles are analyzed for evaporation duct height (EDH), mainly relevant for RF propagation, and for gradients of the modified refractivity at different heights, relevant for both RF and IR propagation. These refractivity gradients are a direct indicator for the occurrence of sub- or super refraction at the height of interest. The present study reveals that under humid and unstable conditions evaporation ducts are found at approximately 3±2 m above cold (5°C) waters and at approximately 8±5 m over warm waters (25°C). Under dry conditions, these duct heights are approximately 9±5 m and 20±10 m, respectively. Duct heights decrease with increasing wind speed. Under humid and near-neutral conditions, duct heights range from 1 to 25 m, and decrease with increasing air temperature and/or wind speed. On the other hand, for dry and near-neutral conditions, and also for neutral conditions, the duct height is not well defined. Values between 1 m and 100 m are found, with an irregular dependence on air temperature and wind speed. Reliable modeling of duct height under these conditions remains questionable due to a lack of vertical mixing in the surface layer. The paper also shows that all four combinations of RF and IR sub- and super-refraction can occur in the atmosphere. The occurrence of a specific combination depends predominantly on temperature and humidity, and to a relatively minor part on wind speed. The magnitude of refraction effects in the two spectral bands is not necessarily coupled but varies with environmental conditions and height. Sub-sub refraction is generally weak and occurs under neutral conditions or at large heights. Super-super refraction occurs under warm and dry conditions and can reach medium strengths. RF-super refraction in combination with IR-sub refraction occurs under strong unstable conditions (e.g., surface temperature higher than air temperature) and can reach medium strengths. RF-sub refraction in combination with IR-super refraction occurs under stable and warm conditions. The magnitude of refraction can be very large, especially at low altitude.

Proceedings Article | 14 October 2005 Paper

RF propagation measurement and model validation during RF/IR synergy trial VAMPIRA

Eric Heemskerk

Proceedings Volume 5981, 598107 (2005) https://doi.org/10.1117/12.637616

KEYWORDS: Atmospheric propagation, Radar, Humidity, Temperature metrology, Radio propagation, Antennas, Infrared radiation, Receivers, Transmitters, Meteorology

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The member nations of AC/323 SET-RTG056/RTG32 on Integration of Radar and Infrared for Ship Self Defence have performed the Validation Measurements for Propagation in the Infrared and Radar (VAMPIRA). The objective was to get insight into the radar and infrared synergy concentrated on propagation in a coastal environment including horizontal inhomogeneity and to validate radar and infrared propagation models. The trial was held in the period 25 March-5 April 2004 near Surendorf Germany. As part of the trial TNO made RF 1-way transmission measurements, 24 hours/day during the whole trial period. The transmission path over the Eckernforder Bucht in Northern Germany had a length of 8.2 km. The transmitted signal was a sweep consisting of 6 frequencies i.e. 3.36, 5.32, 8.015, 9.7, 13.45, and 15.71 GHz. The transmitter height was 11.5 m, the receiver height 6.4 m above 'normal null'. At each end of the path a meteorological station was installed measuring every 30s the air temperature, relative humidity, air pressure, wind speed and wind direction. About halfway the path the TNO meteo buoy was anchored measuring air temperature and relative humidity at 5 heights between 0.65 and 5.15m above the sea surface. Also the sea water temperature was measured by the buoy on a depth of 1m below the sea surface. The effects of evaporation ducting at the propagation at the various frequencies were clearly demonstrated. Some times very deep fadings were present at 13.45 and 15.71 GHz where at the same time almost no effect at 3.36 and 5.32 GHz was observed. The measured propagation at 15.71 GHz was more enhanced than at 13.45 GHz due to the ducting conditions and the elevation angle of the transmitter and receiver antenna. In several sample cases the 1-way propagation factors are computed for every 5 minutes using the propagation model TERPEM (Signal Science) and the vertical refractivity profiles computed by the TNO model TARMOS. The 1-way computed propagation factors compared very well to the measured data at all frequencies, although the computed fadings were not always as deep as the measured ones. A first promising result has been obtained computing the observed height of the RF source under various atmospheric conditions using the transmission phases computed by TERPEM.

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