Dr. Tim A. van Kempen Profile

Dr. Tim A. van Kempen

Instrument/Project Scientist at SRON Netherlands Institute for Space Research

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Publications (6)

Proceedings Article | 27 August 2022 Presentation + Paper

PLATO EM first cryogenic vacuum test campaign PSF results

Francesco Borsa, Andrea Cottinelli, Nicolas Gorius, Claudio Arena, Bart Vandenbussche, Sara Regibo, Rik Huygen, Pierre Royer, Martin Pertenais, Cesar Martin, Thierry Appourchaux, Jose Lorenzo Alvarez, Tim van Kempen, Wouter Laauwen, Isabella Pagano, Roberto Ragazzoni

Proceedings Volume 12180, 121801D (2022) https://doi.org/10.1117/12.2630118

KEYWORDS: Point spread functions, Cameras, Space operations, Error analysis, Cryogenics, Stars, Data analysis, Charge-coupled devices, Telescopes

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Proceedings Article | 27 August 2022 Poster + Paper

Alignment and integration of the first PLATO camera

P. Royer, A. Baeke, G. Terrasa, R. Huygen, S. Regibo, J. Farinato, D. Magrin, A. Mazzoli, M. Pajas, B. Vandenbussche, A. Hermans, G. Millou, D. Vassallo, A. Belén Balado Margeli, L. Clermont, A. Cottinelli, L. Ferrari, N. Gorius, W. Laauwen, Y. Levillain, A. Novi, I. Pagano, M. Pertenais, G. Ramos Zapata, M. Salatti, T. Van Kempen

Proceedings Volume 12180, 121804H (2022) https://doi.org/10.1117/12.2628898

KEYWORDS: Cameras, Staring arrays, Sensors, Interfaces, Optical alignment, Metrology, Mirrors, Charge-coupled devices, Temperature metrology, Image processing, Space telescopes, Space observatories, Observational astronomy

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Proceedings Article | 27 August 2022 Poster + Paper

Ground calibration of the Ariel space telescope: optical ground support equipment design and description

Neil Bowles, Manuel Abreu, Tim van Kempen, Matthijs Krijger, Robert Spry, Rory Evans, Robert Watkins, Cédric Pereira, E. Pascale, Paul Eccleston, Chris Pearson, Lucile Desjonquères, Georgia Bishop, Andrew Caldwell, Andrea Moneti, Mauro Focardi, Subhajit Sarkar, Giuseppe Malaguti, Ioannis Argyriou, Keith Nowicki, Alexandre Cabral, Giovanna Tinetti

Proceedings Volume 12180, 1218049 (2022) https://doi.org/10.1117/12.2627049

KEYWORDS: Calibration, Sensors, Mirrors, Projection systems, Cryogenics, Telescopes, Beam expanders, Spectroscopy, Monochromators, Signal detection

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This paper describes the Optical Ground Support Equipment (OGSE) that is being developed for the payload level testing of the Ariel Space Telescope. Ariel has been adopted as ESA’s “M4” mission in its Cosmic Visions Programme and will launch in 2029 to the second Earth-Sun Lagrange point. During four years of operation the Ariel payload (PL – the cryogenic payload module plus warm units) will perform precise transit spectroscopy of approximately 1000 known exoplanetary atmospheres using a 1.1 m × 0.7 m telescope coupled to two instruments: the Fine Guidance Sensor (FGS) and the Ariel Infrared Spectrometer (AIRS). These instruments provide three spectrometric channels that cover 1.0 to 7.8 μm wavelength range and three photometric channels between 0.5 and 1.1 μm. The Ariel OGSE will verify the optical and radiometric performance of the integrated Ariel PL under vacuum and cryogenic (<40 K) test conditions within the limitations of operation under Earth’s gravity and vibration environments. To achieve these verification requirements the OGSE is integrated with the main Ariel ground test 5 m thermal vacuum chamber. The test chamber contains a cryogenic enclosure (the Cryogenic Test Rig) that surrounds the PL and the OGSE itself comprises of four subsystems. (1) A cryogenic vacuum chamber and integrating sphere illumination module that is fed by visible, near infrared and thermal infrared sources. The illumination module is mounted external to the Ariel test chamber and coupled via a vacuum feedthrough that relays a 22 mm diameter test beam into the Cryogenic Test Rig. The test beam is then relayed using (2) an injection module that steers the beam to maintain alignment during cool-down and scan the Ariel telescope field of view. The beam is then expanded to partially illuminate the Ariel telescope primary mirror using an (3) ~0.3 m diameter target projector collimating mirror. The final optical component of the OGSE is a (4) beam expander placed on the Ariel common optical bench to compensate for the sub-aperture illumination of the primary and to ensure that the spectrometer modules provide illumination with correct cone angles during ground testing. It is planned to use the OGSE in 2026 for a full range of calibration and verification tests of the end-to-end telescope and instrument performance, including detectors, field of view and alignment. These tests will then ensure that Ariel meets it challenging photometric and spectral performance requirements.

Proceedings Article | 27 August 2022 Paper

PLATO camera ghosts: simulations and measurements on the engineering model (EM)

Martin Pertenais, Matthias Ammler-von Eiff, Matteo Burresi, Juan Cabrera, Jacopo Farinato, Nicolas Gorius, Rik Huygen, Demetrio Magrin, Cesar Martin Garcia, Matteo Munari, Sara Regibo, Pierre Royer, Bart Vandenbussche, Tim van Kempen

Proceedings Volume 12180, 121804M (2022) https://doi.org/10.1117/12.2629189

KEYWORDS: Cameras, Stars, Charge-coupled devices, Sensors, Reflection, Point spread functions, Calibration

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Proceedings Article | 11 October 2018 Presentation

Results of TROPOMI-SWIR in-flight calibration (Conference Presentation)

Tim van Kempen, Paul J. Tol, Richard van Hees, Ruud W. Hoogeveen, Ilse Aben

Proceedings Volume 10789, 1078908 (2018) https://doi.org/10.1117/12.2325296

KEYWORDS: Calibration, Short wave infrared radiation, Infrared radiation, Carbon monoxide, Satellites, Atmospheric monitoring, Absorption, Gases, Climatology, Spatial resolution

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TROPOMI (the TROPOspheric Monitoring Instrument) is the single instrument aboard the ESA’s Copernicus Sentinel-5 Precursor (S-5P) satellite launched on October 13, 2017 . S-5P is dedicated to monitoring our atmosphere over a period of at least 7 years. Through spectral absorption features within reflected sunlight, TROPOMI measures total column densities of a large number of gases relevant for air quality and climate. This is done at unprecedented spatial resolution of approximately 3.5-7x7 km2. At this resolution, air pollution at scales of midsized cities can be distinguished from its surroundings. In addition, it can be used to estimate other air pollutant quantities such as aerosols. Each gas has a unique spectral fingerprint across the TROPOMI channels, which range from the UV to the infrared. The Short Wavelength Infrared channel, or SWIR, measures reflected sunlight between wavelengths of 2305 to 2385 nanometers. This channel has been designed to accurately determine methane (CH4) and carbon monoxide (CO) columns To obtain scientifically useful values for both gas species, measured spectra require the SWIR channel to be calibrated to a very high precision and accuracy. The requirements are particularly important for the CH4 product to achieve the ambitious S-5P mission goals. A reliable CH4 product will prove invaluable to the atmospheric scientific community in the next decade. The first six months after the launch of S5-P were used a.o. to execute an in-flight calibration campaign. This campaign was performed as a complement to the on-ground calibration campaign. It was designed to (a) take calibration measurements that were unable to be done on-ground, (b) validate on-ground calibration and (c) prepare for the instrument calibration monitoring during regular operations. Here, we report the calibration results obtained by the SRON Level 1 team for the TROPOMI-SWIR channel. This includes the correct method and settings for background corrections (both dark flux and offset), determination of the initial pixel quality map, the evolution of the background correction and quality map during the first 10 months of flight, validation of the on-ground calibration of the instrumental spectral response function (ISRF) and stray light correction.

Proceedings Article | 14 December 2016 Presentation

Application of new techniques in the calibration of the TROPOMI-SWIR instrument (Conference Presentation)

Paul Tol, Richard van Hees, Tim van Kempen, Matthijs Krijger, Sidney Cadot, Ilse Aben, Antje Ludewig, Jos Dingjan, Stefan Persijn, Ruud Hoogeveen

Proceedings Volume 10000, 100000U (2016) https://doi.org/10.1117/12.2241242

KEYWORDS: Short wave infrared radiation, Calibration, Optical parametric oscillators, Data corrections, Spectroscopy, Satellites, Infrared spectroscopy, Ultraviolet radiation, Aerospace engineering, Sensors

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