Dr. Denis Griessbach Profile

Dr. Denis Griessbach

at Deutsches Zentrum für Luft- und Raumfahrt eV

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Author

Publications (5)

Proceedings Article | 20 October 2023 Presentation + Paper

Laboratory VNIR emissivity of Venus analog rocks and the VEM on VERITAS and the VenSpec-M on EnVision calibration and data verification plan

G. Alemanno, J. Helbert, A. Maturilli, M. Dyar, M. Pertenais, T. Säuberlich, T. Hagelschuer, G. Peter, D. Grießbach, S. Adeli, O. Barraud, A. Van Den Neucker, C. Ytsma, S. Smrekar

Proceedings Volume 12686, 1268606 (2023) https://doi.org/10.1117/12.2678683

KEYWORDS: Calibration, Venus, Equipment, Emissivity, Data modeling, Spectroscopy, Radiometric calibration, Vacuum chambers, Optical filters

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Proceedings Article | 30 August 2022 Poster + Paper

Usage of a Diffractive Optical Element (DOE) for best focal plane estimation of a camera during the integration process

Martin Pertenais, Conor Ryan, Selene Rodd-Routley, Denis Griessbach

Proceedings Volume 12188, 121883Z (2022) https://doi.org/10.1117/12.2627673

KEYWORDS: Diffractive optical elements, Cameras, Sensors, Collimation, Point spread functions, Collimators, Fiber lasers, Spectroscopy, Raman spectroscopy

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Diffractive Optical Elements (DOEs) are commonly used in the photonics community for several purposes, such as geometrical calibration of cameras,1 medical treatments, lithography, LIDAR applications. In the context of the optical alignment and integration of the RAman Spectrometer for MMX (RAX),2 a DOE was included in the test setup with the goal of providing a clear figure of merit to optimize the focusing of a dioptric lens objective on to the spectrometer detector. This Raman spectrometer will be integrated later this year in a small Rover on-board the Martian Moons eXploration (MMX) mission led by JAXA, and will operate on Phobos’ surface to characterize the different materials composing Phobos’ soil. To achieve this, the optical design of RAX is very challenging in terms of performance to reach in very limited volume and mass. As described in Ref. 2, the optical alignment and integration of RAX was a very challenging exercise, requiring several optical setups and methods. The usage of a DOE was introduced to solve a classical problem during the integration of a camera: how to integrate both the optical objective (lens assembly) and the detector to ensure that both the optical focal plane and the detector sensitive plane are co-planar. When illuminated by a collimated laser beam, the implemented DOE generates a regular pattern of collimated beams with well-known deviation angles from the input beam. It acts as a 2D diffraction grating, and generates a pattern field which covers the entire field of view of our camera. Thanks to this property, the Camera Interface Objective of RAX could be successfully positioned and oriented with respect to the detector mechanical interface. It was achieved by acquiring successive images of the DOE pattern with controlled defocused laser beam illuminating it. We were then able to compute the equivalent mechanical defocus needed to maximize the image quality. This maximizes the overall instrument performance and will ensure best possible scientific measurement on Phobos.

Proceedings Article | 11 June 2021 Open Access

The unique field-of-view and focusing budgets of PLATO

Martin Pertenais, Juan Cabrera, Carsten Paproth, Anko Boerner, Denis Grießbach, Valery Mogulsky, Heike Rauer

Proceedings Volume 11852, 118524Y (2021) https://doi.org/10.1117/12.2599820

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The PLAnetary Transits and Oscillations of stars mission (PLATO) is the M3 mission in ESA’s Cosmic Vision 2015-2025 Programme, see Rauer et al. (2014).¹ The PLATO mission aims at detecting and characterizing extrasolar planetary systems, including terrestrial exoplanets around bright solar-type stars in the habitable zone. In order to achieve its scientific objectives, PLATO must perform uninterrupted high precision photometric monitoring of large samples of stars during long periods to detect and characterize planetary transits. The scientific payload of PLATO, developed and provided by the PLATO Mission Consortium (PMC) and ESA, is based on a multi-telescope configuration consisting of 24 “Normal” (N) cameras and 2 “Fast” (F) cameras, so as to provide simultaneously a large field of view and a large collecting aperture. The optical design is identical for all cameras and consists of a 6-lens dioptric design with a 120 mm entrance pupil and an effective field of view of more than 1000 deg2. This concept results in an overall field-of-view of more than 2000 deg², spread over 104 CCDs of 20 mega-pixels each. Associated to very accurate pointing and alignment requirements, this is a real challenge to define and breakdown precise specifications to several sub-systems in order to ensure that this overall field of view budget is achieved and verified. We propose to go through the budget that was performed for the PLATO camera and to describe how we intend to satisfy this scientific requirement. To make it more challenging, it has to be taken into account that the PLATO spacecraft will have to rotate of 90° every three months without changing its field of view (due to its orbit in L2 and the sun illumination limitations). This has to be considered in the breakdown of the budget and design of all sub-systems. A consequence of this large field of view is the difficulty to reach very good and harmonious optical performances across the field, and in a realistic depth of focus. Therefore, the focusing budget is also very challenging for the development of the PLATO cameras. We will describe the way the PLATO’s camera focusing budget has been broken down into allocations and how it is planned to be verified. To ensure optimal performances in-flight, the PLATO cameras have the extraordinary capabilities to perform re-focusing using a high precision Thermal Control System (TCS). Each individual camera on the payload can be thermally controlled independently from its neighbor to reach its own optimal operational temperature. The different consequences of this concept into the budget allocations and sub-system development will be discussed.

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Proceedings Article | 11 June 2021 Open Access

The fine guidance system of the PLATO mission

Denis Grießbach, Ulrike Witteck, Carsten Paproth

Proceedings Volume 11852, 118523H (2021) https://doi.org/10.1117/12.2599604

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Proceedings Article | 11 June 2021 Open Access

Overview of PLATO’s cameras on-ground and in-orbit calibration and characterisation

Martin Pertenais, Juan Cabrera, Denis Griessbach, Anders Erikson, Bart Vandenbussche, Réza Samadi, Daniel Reese, Heike Rauer

Proceedings Volume 11852, 1185209 (2021) https://doi.org/10.1117/12.2599149

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The PLAnetary Transits and Oscillations of stars mission (PLATO) is the M3 mission in ESA’s Cosmic Vision 2015-2025 Programme. The PLATO mission aims at detecting and characterizing extrasolar planetary systems, including terrestrial exoplanets around bright solar-type stars in the habitable zone. In order to achieve its scientific objectives, PLATO must perform uninterrupted high precision photometric monitoring of large samples of stars during long periods to detect and characterize planetary transits. The PLATO light curves will also contain information on the seismic activity of the stars, which will lead to the determination of radii and ages of parent stars. The scientific payload of PLATO, developed and provided by the PLATO Mission Consortium (PMC), is based on a multi-telescope configuration consisting of 24 “Normal” (N) cameras and 2 “Fast” (F) cameras, so as to provide simultaneously a large field of view and a large collecting aperture. The optical design is identical for all cameras and consists of a 6-lens dioptric design with a 120 mm entrance pupil and an effective field of view of more than 1000 deg2. The calibration and characterization of PLATO’s cameras is a real challenge, especially in terms of quantities: there are 24 FMs + 2 Flight Spares + 2 Qualification Models and finally 1 EM to calibrate. In this context, the on-ground calibration and characterization plan of the cameras was developed to the strict minimum needed. This means that all the measurements that can be performed in-orbit will not be calibrated on-ground. Our aim is to give an overview of the on-ground activities planned in the coming years to calibrate, characterize and verify the PLATO’s cameras, both in terms of organization and technical solutions. In particular, a detailed description of the geometric calibration used for the Fine Guidance System (FGS) and the focusing calibration will be given. PLATO’s Cameras have indeed the unusual but powerful feature to use a temperature control system to refine their focus. A description of the in-flight calibration plan (including for example the repetition of the focusing calibration, the micro-scanning procedure to determine high-resolution PSFs) will then be given to get the full overview of the calibration, characterization and verification of PLATO’s cameras. Calibrating and verify so many cameras in space, without any calibration targets/sources on board, only using pointing capabilities of the satellite, stellar targets and advanced data processing is a real challenge for this mission. A particular attention will be given to the micro-scanning procedure and inversion techniques required for precise PSF Modelling.

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