Unspecified Berit Ahlers Profile

Berit Ahlers

at European Space Research and Technology Ctr

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Publications (11)

Proceedings Article | 12 July 2023 Open Access

COPERNICUS Sentinel-4: calibration campaign results and performances

G. Bazalgette Courrèges-Lacoste, O. Seger, B. Oexl, M. Harlander, S. Riedl, S. Becher, J.-F. Pittet, B. Ahlers, A. Chanumolu, M. Miler, Y. Aoun, A. Pasquet, M. Dobber, F. Ruethrich, S. Gimeno Garcia

Proceedings Volume 12777, 1277735 (2023) https://doi.org/10.1117/12.2690338

KEYWORDS: Equipment, Calibration, Polarization, Light sources and illumination, Radiometric calibration, Stray light, Spectral response, Spectral calibration, Light sources, Sun

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Proceedings Article | 5 March 2021 Presentation + Paper

Smart slit assembly employing continuously tunable MEMS shutter

Anton Lagosh, Gergely Huszka, Hamed Sattari, Berit Ahlers, Benedikt Guldimann, Grégoire Kerr, Mauro Melozzi, Peyman Rahnama, Takeshi Nishizawa, Niels Quack

Proceedings Volume 11697, 116970P (2021) https://doi.org/10.1117/12.2583149

KEYWORDS: Microelectromechanical systems, Camera shutters, Wafer-level optics, Silica, Modulation, Waveguides, Vapor etching, Spectrometers, Silicon, Semiconducting wafers

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Proceedings Article | 12 July 2019 Open Access

Sentinel 4 UVN: a geostationary imaging UVN spectrometer for air quality monitoring: performance, measurement modes and model philosophy

S. Riedl, M. Harlander, C. Schlosser, M. Kolm, R. Maurer, G. Bazalgette Courrèges-Lacoste, C. Pachot, B. Ahlers, S. Grabarnik, L. Gambicorti, M. Sallusti, G. Bulsa, G. Bagnasco

Proceedings Volume 11180, 1118005 (2019) https://doi.org/10.1117/12.2535924

KEYWORDS: Calibration, Near infrared, Sun, Spectroscopy, Polarization, Scanners, Mirrors, Sensors, Telescopes, Light sources

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Proceedings Article | 21 November 2017 Open Access

Combined Raman/LIBS spectrometer elegant breadboard: built and tested - and flight model spectrometer unit

B. Ahlers, I. Hutchinson, R. Ingley

Proceedings Volume 10566, 105662H (2017) https://doi.org/10.1117/12.2308293

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A spectrometer for combined Raman and Laser Induced Breakdown Spectroscopy (LIBS) is amongst the different instruments that have been pre-selected for the Pasteur payload of the ExoMars rover. It is regarded as a fundamental, next-generation instrument for organic, mineralogical and elemental characterisation of Martian soil, rock samples and organic molecules. Raman spectroscopy and LIBS will be integrated into a single instrument sharing many hardware commonalities [1]. The combined Raman / LIBS instrument has been recommended as the highest priority mineralogy instrument to be included in the rover’s analytical laboratory for the following tasks: Analyse surface and sub-surface soil and rocks on Mars, identify organics in the search for life and determine soil origin & toxicity.

The synergy of the system is evident: the Raman spectrometer is dedicated to molecular analysis of organics and minerals; the LIBS provides information on the sample’s elemental composition. An international team, under ESA contract and with the leadership of TNO Science and Industry, has built and tested an Elegant Bread Board (EBB) of the combined Raman / LIBS instrument. The EBB comprises a specifically designed, extremely compact, spectrometer with high resolution over a large wavelength range, suitable for both Raman spectroscopy and LIBS measurements. The EBB also includes lasers, illumination and imaging optics as well as fibre optics for light transfer.

A summary of the functional and environmental requirements together with a description of the optical design and its expected performance are described in [2]. The EBB was developed and constructed to verify the instruments’ end-to-end functional performance with natural samples. The combined Raman / LIBS EBB realisation and test results of natural samples will be presented.

For the Flight Model (FM) instrument, currently in the design phase, the Netherlands will be responsible for the design, development and verification of the spectrometer unit, while the UK provides the detector. The differences between the EBB and the FM will be demonstrated.

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Proceedings Article | 21 November 2017 Open Access

Multi-parameter fibre Bragg grating sensor-array for thermal vacuum cycling test

L. Cheng, B. Ahlers, P. Toet, G. Casarosa, M. Appolloni

Proceedings Volume 10566, 105661E (2017) https://doi.org/10.1117/12.2308294

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Fibre Bragg Grating (FBG) sensor systems based on optical fibres are gaining interest in space applications. Studies on Structural Health Monitoring (SHM) of the reusable launchers using FBG sensors have been carried out in the Future European Space Transportation Investigations Programme (FESTIP). Increasing investment in the development on FBG sensor applications is foreseen for the Future Launchers Preparatory Programme (FLPP). TNO has performed different SHM measurements with FBGs including on the VEGA interstage [1, 2] in 2006.

Within the current project, a multi-parameter FBG sensor array demonstrator system for temperature and strain measurements is designed, fabricated and tested under ambient as well as Thermal Vacuum (TV) conditions in a TV chamber of the European Space Agency (ESA), ESTEC site. The aim is the development of a multi-parameters measuring system based on FBG technology for space applications. During the TV tests of a Space Craft (S/C) or its subsystems, thermal measurements, as well as strain measurements are needed by the engineers in order to verify their prediction and to validate their models. Because of the dimensions of the test specimen and the accuracy requested to the measurement, a large number of observation/measuring points are needed. Conventional sensor systems require a complex routing of the cables connecting the sensors to their acquisition unit. This will add extra weight to the construction under test. FBG sensors are potentially light-weight and can easily be multiplexed in an array configuration.

The different tasks comply of a demonstrator system design; its component selection, procurement, manufacturing and finally its assembly. The temperature FBG sensor is calibrated in a dedicated laboratory setup down to liquid nitrogen (LN₂) temperature at TNO. A temperature-wavelength calibration curve is generated. After a test programme definition a setup in thermal vacuum is realised at ESA premises including a mechanical strain transducer to generate strain via a dedicated feed through in the chamber. Thermocouples are used to log the temperature for comparison to the temperature FBG sensor. Extreme temperature ranges from -150°C and +70°C at a pressure down to 10-4 Pa (10-6 mbar) are covered as well as testing under ambient conditions. In total five thermal cycles during a week test are performed. The FBG temperature sensor test results performed in the ESA/ESTEC TV chamber reveal high reproducibility (within 1 °C) within the test temperature range without any evidence of hysteresis. Differences are detected to the previous calibration curve. Investigation is performed to find the cause of the discrepancy. Differences between the test set-ups are identified. Equipment of the TNO test is checked and excluded to be the cause. Additional experiments are performed.

The discrepancy is most likely caused by a ’thermal shock’ due to rapid cooling down to LN2 temperature, which results in a wavelength shift. Test data of the FBG strain sensor is analysed. The read-out of the FBG strain sensor varies with the temperature during the test. This can be caused by temperature induced changes in the mechanical setup (fastening of the mechanical parts) or impact of temperature to the mechanical strain transfer to the FBG. Improvements are identified and recommendations given for future activities.

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Proceedings Article | 21 November 2017 Open Access

Combined raman spectrometer/laser-induced breakdown spectrometer design concept

Gregory Bazalgette Courrèges-Lacoste, Berit Ahlers, Erik Boslooper, Fernando Rull-Perez, Sylvestre Maurice

Proceedings Volume 10567, 105671U (2017) https://doi.org/10.1117/12.2308176

KEYWORDS: Raman spectroscopy, Laser induced breakdown spectroscopy, Mars, Spectroscopy, Minerals, Chemical analysis, Statistical analysis, Luminescence, Spectrometer engineering, Plasma

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Proceedings Article | 21 November 2017 Open Access

Vega interstage strain measurements: comparison between conventional strain gauges and fibre Bragg grating sensors

Lun Cheng, Berit Ahlers

Proceedings Volume 10567, 105672E (2017) https://doi.org/10.1117/12.2308159

KEYWORDS: Fiber Bragg gratings, Sensors, Satellites, Temperature metrology, Modulation, Aerospace engineering, Wavelength division multiplexing, Optical fibers, Visualization, Telescopic pixel displays

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Proceedings Article | 4 September 2009 Paper

Moon4You: a combined Raman/LIBS instrument for lunar exploration

Erik Laan, Berit Ahlers, Wim van Westrenen, Jeannette Heiligers, Arno Wielders

Proceedings Volume 7441, 744114 (2009) https://doi.org/10.1117/12.825883

KEYWORDS: Laser induced breakdown spectroscopy, Raman spectroscopy, Aerospace engineering, Chemical elements, Spectroscopy, Scientific research, Space operations, Solar system, Soil science, Oxygen

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SPIE Journal Paper | 1 March 2008

Optical design of a combined Raman–laser-induced-breakdown-spectroscopy instrument for the European Space Agency ExoMars Mission

Isabel Escudero-Sanz, Berit Ahlers, Gregory Bazalgette Courreges-Lacoste

OE, Vol. 47, Issue 03, 033001, (March 2008) https://doi.org/10.1117/12.10.1117/1.2896453

KEYWORDS: Raman spectroscopy, Laser induced breakdown spectroscopy, Spectroscopy, Optical design, Head, Channel projecting optics, Optical fibers, Mirrors, Sensors, Signal to noise ratio

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Proceedings Article | 15 September 2005 Paper

Darwin Infrared Nulling Interferometer Demonstrator

L. Vosteen, B. Ahlers

Proceedings Volume 5905, 59050B (2005) https://doi.org/10.1117/12.613876

KEYWORDS: Wavefronts, Interferometers, Planets, Infrared radiation, Nulling interferometry, Space telescopes, Destructive interference, Polarization, Polarizers, Mirrors

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Proceedings Article | 4 November 2004 Paper

In-orbit detection of spectral features in SCIAMACHY

Berit Ahlers, Gregory Bazalgette Courreges-Lacoste, Coen Schrijvers, Hedser van Brug

Proceedings Volume 5570, (2004) https://doi.org/10.1117/12.565565

KEYWORDS: Diffusers, Sun, Electronic support measures, Signal detection, Calibration, Feature extraction, Earth's atmosphere, Fabry–Perot interferometers, Telescopic pixel displays, Gases

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Showing 5 of 11 publications

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