Veröffentlichungen

│2016

A comprehensive stray-light analysis of the Euclid NISP instrument

Grupp, F.; Lange, E.; Geis, N.; Prieto, E.; Bender, R.

Abstract: An ASAP analysis has been conducted for the CDR of the EUCLID-NISP near infra-red instrument. The results are presented and compared to analytical estimates as well as to a previously published ZEMAX study. In order to have a profound basis for our dust modelling we compare the model parameters to measurements of actual lenses that where pre-contaminated (and cleaned again) in our facilities. Special attention is drawn on the modelling of structural parts, as well as on the baffling structures. Complex light paths are identified along the mechanics to show the depth of analysis that is possible in such a study.

Final tolerancing approach and the value of short-cutting tolerances by measurement

Grupp, F.; Prieto, E.; Geis, N.; Bode, A.; Bodendorf, C.; Costille, A.; Katterloher, R.; Penka, D.; Bender, R.

Proc. SPIE 9904, Space Telescopes and Instrumentation 2016: Optical, Infrared, and Millimeter Wave, 99042M (29 July 2016); doi: 10.1117/12.2231362

Abstract: Within the ESAs 2015 - 2025 Cosmic Vision framework the 1.2 m aperture EUCLID space telescope addresses cosmological questions related to dark matter and dark energy. Being equipped with two instruments that are simultaneously observing patches of > 0.5 square degree on the sky EUCLID is aiming at major cosmological probes in a large seven years survey scanning the entire extragalactic sky. These two instruments, the visual light high spacial resolution imager (VIS) and the near infrared spectrometer and photometer (NISP) are separated by a dichroic beam splitter. Its huge field of view (FoV) - larger than the full moon disk - together with high demands on the optical performance and strong requirements on in flight stability lead to very challenging demands on alignment and post launch – post cool-down optical element position. The role of an accurate and trust-worthy tolerance analysis which is well adopted to the stepwise integration and alignment concept, as well as to the missions stability properties is therefore crucial for the missions success. While the previous contributions of this series of papers (e.g.[1])was addressing the technical aspects of tolerancing, the mechanical challenges and the answers of the NISP instrument to these challenges, this paper will focus on our concept of shortcutting the tolerance chain by measurement wherever useful and possible. The NISP instrument is only possible, due to the innovative use of technologies such as computer generated hologram (CGH) based manufacturing and alignment. Expanding this concept, certain steps in the assembly process, such as focal length determination before detector placement allow to reduce the overall tolerance induced imaging errors. With this papers we show three major examples of this shortcutting strategy.

Performance measurement of high precision optical assemblies for cosmological observations: Comparison of different approaches

Bodendorf, C.; Bode, A.; Geis, N.; Grupp, F.; Bender, R.

Proc. SPIE 10009, Third European Seminar on Precision Optics Manufacturing, 100090F (June 30, 2016); doi:10.1117/12.2235210

Abstract: Euclid is the name of a space telescope currently being developed in the framework of the ESA Cosmic Vision 2015-2025 Program. It addresses cosmological questions related to dark matter and dark energy. The lens system of one of the two scientific key instruments on board of Euclid (a combined near-infrared spectrometer and photometer) is designed and tested at the Max Planck Institute for Extraterrestrial Physics.
In this paper, we compare two complementary approaches to determine the imaging quality of the photometer. The first approach is based on a direct camera measurement of the point-spread function (PSF) while the second approach uses a Shack-Hartmann sensor to reconstruct the wave front of the system.
Both methods yield in principle largely overlapping information in terms of e.g. modulation transfer function (MTF), encircled energy (EE) or spot shape. However, the experimental requirements are quite different. Details like the spatial extent and coherence properties of the object have different impact and are essential for the degree of agreement between both approaches. Moreover, the disturbance due to measurement noise is quite unequal and requires different evaluation steps.
The pros and cons of both methods that actually complement one another are investigated and discussed.

│2015

Preliminary results on the EUCLID NISP stray-light and ghost analysis

Geis, N.; Grupp, F.; Prieto, E.; Bender, R.

Proc. SPIE 9602, UV/Optical/IR Space Telescopes and Instruments: Innovative Technologies and Concepts VII, 96020H (22 September 2015); doi: 10.1117/12.2187948

Abstract: The EUCLID mission within the European Space Agencies 2015 - 2025 Cosmic Vision framework addresses cosmological questions related to dark matter and dark energy. EUCLID is equipped with two instruments that are simultaneously observing patches of > 0:5 square degree on the sky. The VIS visual light high spacial resolution imager and the NISP near infrared spectrometer and photometer are separated by a di-chroic beam splitter. With its large FoV (larger than the full moon disk), together with high demands on the optical performance and strong requirements on in flight stability lead to very challenging demands on alignment and post launch { post cool-down optical element position. In addition the demanding requirements from spectroscopy and galaxy photometry lead to a highly demanding stray light and ghost control need. With this paper we present a preliminary - PDR level - analysis of ghosting and stray light levels in the EUCLID NISP near infrared spectrometer and photometer. The analysis presented focuses on the photometric channel, as this, together with the wide field of the instrument, shows most of the challenges and features of the instrument. As one requirement is to have a non vignetting design, extensive baffling is not possible, and only secondary and higher order light can be actively baffled. A comprehensive ZEMAX based analysis is being presented, showing in summary that baffles are only necessary due to the EUCLID fine guiding sensors auxiliary fields of view. The total level of contaminating light is thereafter dominated by stray light from dust on the lenses. Ghosts play a minor role.

Temperature-dependent refractive index measurements of CaF2, Suprasil 3001, and S-FTM16 for the Euclid near-infrared spectrometer and photometers

Douglas B. Leviton; Kevin H. Miller; Manuel A. Quijada; Frank U. Grupp

Proc. SPIE 9578, Current Developments in Lens Design and Optical Engineering XVI, 95780M (3 September 2015); doi: 10.1117/12.2189024

Abstract: Using the Cryogenic High Accuracy Refraction Measuring System (CHARMS) at NASA’s Goddard Space Flight Center, we measured absolute refractive indices at temperatures from 100 to 310 K at wavelengths from 0.42 to 3.6 microns for CaF₂, Suprasil 3001 fused silica, and S-FTM16 glass in support of lens designs for the Near Infrared Spectrometer and Photometer (NISP) for ESA’s Euclid dark energy mission. We report absolute refractive index, dispersion (dn/dλ), and thermo-optic coefficient (dn/dT) for these materials. In this study, materials from different melts were procured to understand index variability in each material. We provide temperature-dependent Sellmeier coefficients based on our data to allow accurate interpolation of index to other wavelengths and temperatures. For calcium fluoride (CaF₂) and S-FTM16, we compare our current measurements with CHARMS measurements of these materials made in the recent past for other programs. We also compare Suprasil 3001’s indices to those of other forms of fused silica we have measured in CHARMS.

│2014

The EUCLID NISP tolerancing concept and results

Grupp, F.; Prieto, E.; Geis, N.; Bode, A.; Katterloher, R.; Bodendorf, C.; Penka, D.; Bender, R.

Proc. SPIE. 9143, Space Telescopes and Instrumentation 2014: Optical, Infrared, and Millimeter Wave, 91432X. (August 02, 2014) doi: 10.1117/12.2055398

Abstract: Within ESAs 2015 - 2025 Cosmic Vision framework the EUCLID mission satellite addresses cosmological questions related to dark matter and dark energy. EUCLID is equipped with two instruments that are simultaneously observing patches of > 0.5 square degree on the sky. The VIS visual light high spacial resolution imager and the NISP near infrared spectrometer and photometer are separated by a di-chroic beam splitter. Having a large FoV (larger than the full moon disk), together with high demands on the optical performance and strong requirements on in flight stability lead to very challenging demands on alignment and post launch { post cool-down optical element position. The role of an accurate and trust-worthy tolerance analysis which is well adopted to the stepwise integration and alignment concept, as well as to the missions stability properties is therefore crucial for the missions success. With this paper we present a new iteration of the baseline tolerancing concept for EUCLID NISP. All 7 operational modes being low resolution slit-less spectroscopy and three band Y, J& H+ band photometry are being toleranced together. During the design process it was noted that the desired performance can only be reached when alignment and tolerancing methods are closely connected and optimized together. Utilizing computer generated - multi zone - holograms to align and cross reference the four lenses of the NISP optical system. We show our plan to verify these holograms and what alignment sensitivities we reach. In the main section we present the result of the tolerancing and the main contributers that drive the mechanical and thermal design of the NISO optical subsystems. This analysis presents the design status of NISP at the system PDR of the mission.

│2013

Radiation damage to six selected optical materials

Grupp, F.; Geis, N.; Katterloher, R.; Bender, R.

Proc. SPIE. 8860, UV/Optical/IR Space Telescopes and Instruments: Innovative Technologies and Concepts VI, 88600N. (September 26, 2013) doi: 10.1117/12.2023252

Abstract: The ESA/EUCLID satellite is equipped with two instruments that are simultaneously observing patches of > 0:5 square degree on the sky. The VIS visual light high spacial resolution imager and the NISP near infrared spectrometer and photometer are separated by a di-chroic beam splitter.
The NISP Near Infrared Spectrometer and Photometer reduces the initial f/# 20 beam of the Korsch type telescope to an f/# 10 beam filling 16 Hawaii 2RG detectors on the NISP instrument focal plane by means of a four lens optical system.
With this paper we present tests on the radiation damage measured between 500 and 2000nm to six 25mm thick probes of optical materials potentially used in the NISP optics for the environmental conditions expected for a six years mission in the outer Lagrange point L2.

A tolerancing approach taking into account the interferometric alignment scheme of the EUCLID NISP space optics

Grupp, F.; Prieto, E.; Spano, P.; Geis, N.; Bode, A.; Katterloher, R.; Bodendorf, C.; Becker, M.; Bogner, S.; Bender, R.

Proc. SPIE 8860, UV/Optical/IR Space Telescopes and Instruments: Innovative Technologies and Concepts VI, 88600G (September 26, 2013); doi:10.1117/12.2023264

Abstract: The ESA/EUCLID satellite is equipped with two instruments that are simultaneously observing patches of < 0:5 square degree on the sky. The VIS visual light high spacial resolution imager and the NISP near infrared spectrometer and photometer are separated by a di-chroic beam splitter. The huge field of view, together with the enormous demands on the optical performance and in flight stability of the instruments and telescope lead to unique demands in post launch alignment. A very detailed, very well set up optical tolerance analysis is therefore one key point in the success of the mission. Design and alignment have to be optimized for best toleranced performance. This paper presents the baseline concept of the NISP instrument with its two observational modes being low resolution slit-less spectroscopy and three band J, H&K+ photometry. Special chapters deal with the alignment scheme and the derived tolerance approach which will be used towards the instrument PDR.

│2012

The optical baseline concept of the NISP near infrared spectrometer and photometer on board of the ESA/EUCLID satellite

Grupp, F.; Prieto, E.; Geiss, N.; Bode, A.; Katterloher R.; Grange, R.; Junk, V.; Bender, R.

Proc. SPIE. 8442, Space Telescopes and Instrumentation 2012: Optical, Infrared, and Millimeter Wave, 84420X. (August 22, 2012) doi: 10.1117/12.925645

Abstract: The ESA/EUCLID satellite is equipped with two instruments that are simultaneously observing patches of > 0:5 square degree on the sky. The VIS visual light high spacial resolution imager and the NISP near infrared spectrometer and photometer are separated by a di-chroic beam splitter. This paper shows the baseline concept of the NISP instrument with its two observational modes being low resolution slit-less spectroscopy and three band J, H and K+ photometry. The drivers for the optical design, the nominal performance as well as the tolerancing approach for NISP are being presented. The impact of the tolerance approach and the tight tolerances on the opto-mechanical design, assembly, integration and verification is addressed in a special section of this paper.

│2011

The Euclid-NISP instrument optics and tolerancing approach

Grupp, F.; Prieto, E.; Spano, P.; Zerbi, F. M.; Geis, N.; Bode, A.; Junk, V.; Bender, R.

Proc. SPIE. 8146, UV/Optical/IR Space Telescopes and Instruments: Innovative Technologies and Concepts V, 81460R. (September 08, 2011) doi: 10.1117/12.893646

Abstract: The European ESA EUCLID dark energy, dark matter mission is presented with respect to the near instrument optics. We present the nominal optics approach as well as the tolerancing concept and the results of this tolerancing. through this we are able to show that the merged near infrared spectrometer and photometer NISP can be built with high image quality in a sophisticated but well performing approach. Furthermore a ghost analysis for NISP is presented, showing that reflective ghost have been successfully suppressed during the optimization process.