Mr. Eyk Gebhardt Profile

Eyk Gebhardt

at Jena-Optronik GmbH

SPIE Involvement:

Author

Publications (4)

Proceedings Article | 11 June 2021 Open Access

Alignment turning and assembly of the Sentinel 4 optical modules

Andreas Gebhardt, Erik Schmidt, Torsten Hertel, Steffen Kirschstein, Eyk Gebhardt, Thomas Rendel, Ute Gawronski, Vinzenz Wand

Proceedings Volume 11852, 118522X (2021) https://doi.org/10.1117/12.2599458

Read Abstract +

Centering and positioning of the single optical elements within a lens system are essential for the quality of high precision optics. The positioning of the lenses have to be long term stable and shall withstand space environment to keep the performance of the optical system over years. This applies in particular to the optical modules for the Sentinel-4/Ultraviolet/Visible/Near-Infrared (UVN) sounder instrument /1/. In order to fulfill these requirements an appropriate opto-mechanical design and a deterministic assembly technique based on well-defined assembly interfaces are essential. For this reason, the application of the alignment turning technology is particularly suitable /2/. The basic approach is to reach the best possible coincidence between the optical axis of the lens and the mechanical axis of the lens cell and drop the lens stack in a barrel with a tight fitting. By machining the lens housing in respect to the optical axis the resulting ultra-precise references planes significantly simplify the alignment and integration of the objective. The assembly becomes deterministic – extensive alignments are not required. The mechanical and environmental specifications are achieved by the consistent compliance with: ultra-precise machined mounting interfaces, avoiding adjustment mechanisms, the application of a defined pre load during lens mounting. The S4 UVN optical modules requires a resulting decenter shift of each optical surface to the best fitting optical system axis less than 4 µm for the telescope, camera and collimator optics and less than 6 µm for the NIR optics. The total tilt of each surface to the best fitting optical axis has to be within 6 arcsec. The individual lens position (air distances) as well as the position of the lens stack in direction of the optical axis have to be within 5 µm, respectively. Aiming to the specified values the alignment turning technology was carried out on the proto flight models of the UVN instrument optics. Using a customized alignment turning machine the decentration of the housed lens were detected and adjusted in respect to the turning axis, reaching a minimum. After machining of the housing the vertex height as well as the geometry of the lens cell were measured in sub micron precision. For the passive joining of the alignment turned lens elements in to the lens tube without further adjustment steps a specific mounting device was realized. A newly developed clamping process that ensures a dedicated pre-load completes the assembly procedure. The alignment turned and assembled flight models were characterized using a centration measurement of the optical subsystems (telescope, collimator, camera, NIR spectrometer). The alignment status of the optical axis of all individual lens systems w.r.t. the measurement reference axis was determined within the required specifications. Further optical verification measurements confirm the achieved optical performance of the optical modules to the full extent. The paper deals with the alignment turning, the integration and verification of the lens assemblies for the S4 UVN Instrument.

DOWNLOAD PAPER

Proceedings Article | 11 June 2021 Open Access

SENTINEL-4 combined optical assemblies

Simon Chelkowski, Steffen Kirschstein, Torsten Hertel, Ute Gawronski, Steffen Rienecker, Eyk Gebhardt

Proceedings Volume 11852, 1185233 (2021) https://doi.org/10.1117/12.2599530

Read Abstract +

The ESA Sentinel-4 Mission is part of the European Commission Copernicus Programme for monitoring the Earth. It is going to provide free data on trace gas concentrations and aerosols in the atmosphere to support real time operational services of air-quality for Europe. The Sentinel-4/UVN Instrument will be placed in a geo-stationary orbit on board of the Meteosat Third Generation Sounder (MTG-S) satellite. Jena-Optronik has been contracted to develop and build the core main optics of the Sentinel-4/Ultra-violet/Visible/Near- Infrared (UVN) instrument, which comprises a telescope, a UV-VIS spectrometer and a NIR spectrometer. Due to its geo-stationary orbit and its compactness the photon flux seen by the instrument is low. Simultaneously the lens based optics of the instrument set new standards concerning performance. In consequence straylight levels within the instrument need to be reduced to the bare minimum including high quality polishing of the optics as well as manufacturing facilities as well as processes, which reduce the overall allowed contamination of the optical surfaces to be <50ppm for particular and <50ng/cm² molecular contamination. Furthermore, the very demanding performance requirements led to an instrument design, which sets the demands on manufacturing and alignment quality to a new level. To realize the instruments performance over the complete specified thermal range Jena-Optronik developed a unique passive thermal focus compensation for the lens optics, which acts like a passive auto-focus system w.r.t. thermal changes. Moreover, we used precision lens mount manufacturing techniques to achieve the required lens positioning accuracy of less than 5μm. The design of the instrument will be presented as well as the highlights from the assembly, integration and test campaign of the three core optics. All three PFMs, the telescope as well as the UV-VIS and the NIR spectrometers have been successfully delivered to Airbus Defence & Space after ending their environmental test campaign successfully.

DOWNLOAD PAPER

Proceedings Article | 20 September 2020 Presentation

Sentinel-4 combined optial assemblies

Steffen Kirschstein, Torsten Hertel, Ute Gawronski, Steffen Rienecker, Eyk Gebhardt, Simon Chelkowski

Proceedings Volume 11530, 115300E (2020) https://doi.org/10.1117/12.2573015

KEYWORDS: Optics manufacturing, Spectroscopy, Telescopes, Near infrared, Contamination, Aerosols, Earth's atmosphere, Atmospheric monitoring, Atmospheric optics, Atmospheric particles

Read Abstract +

Proceedings Article | 5 September 2017 Presentation + Paper

The Sentinel-4 UVN focal plane assemblies

Jürgen Hinger, Rüdiger Hohn, Eyk Gebhardt, Jörg Reichardt

Proceedings Volume 10402, 1040217 (2017) https://doi.org/10.1117/12.2274344

KEYWORDS: Staring arrays, Gases, Mirrors, Reflector telescopes, Telescopes

Read Abstract +

View contact details

UPDATE YOUR PROFILE

Is this your profile? Update it now.

Sign into your SPIE.org account

Don’t have a profile and want one?

Create an account on SPIE.org

Keywords/Phrases

Search In:

Publication Years