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Euclid is an European Space Agency (ESA) mission to map the geometry of the Dark Universe. The mission will investigate the distance-redshift relationship and the evolution of cosmic structures. It achieves this by measuring shapes and redshifts of galaxies and clusters of galaxies out toredshifts ~2, or equivalently to a look-back time of 10 billion years. It will therefore cover the entire period over which dark energy played a significant role in accelerating the expansion. The Near-Infrared Spectrograph and Photometer (NISP) role is to measure the galaxies' redshift. The baseline for NISP is an infrared instrument allowing observation in slitless "spectrography" mode thanks to several Grisms, or in "photometry" mode using several filters.

NISP Opto Mechanical Assembly (NI-OMA)

Fig. 1. Design of NI-OMA + NI-DS

Fig. 1. Design of NI-OMA + NI-DS

The NISP Opto-Mechanical Assembly (NI-OMA) is composed of:

NI-OA: Optical Assembly: consists in a corrective optic (CoLA) and a camera optic (CaLA)
- The CaLA accommodates three aspherical lenses (L1; L2 & L3), which are mounted by using adaption rings inside a lens barrel.
- The CoLA system consists of the corrector lens (L4) and its adaption ring.
NI-SA: Structure Assembly: a structure in SiC (Silicon Carbide)
NI-FWA: Filter Wheel Assembly: carries 3 Filters
NI-GWA: Grism Wheel Assembly: carries 4 Grisms

Both wheels are equipped with a cryomechanism

NI-CU: Calibration Unit
NI-TC: Thermal Control which objective is to control the optics at the temperature of 140K ±0.3 K during all the lifetime.

Fig. 2. Mock up of NI-OMA + NI-DS

© LAM

Fig. 2. Mock up of NI-OMA + NI-DS

© LAM

NI-OA Design

Camera Lens Assembly (CaLA)

The Camera Lens Assembly (CaLA) accommodates three aspherical lenses, which are mounted by using adaption rings inside a lens barrel.

http://www.mpe.mpg.de/1020209/Optisches-Design

Fig. 4. Actual design of CaLA.

Fig. 4. Actual design of CaLA.

Fig. 5. Actual Design of CoLA

Fig. 5. Actual Design of CoLA

Corrector Lens Assembly (CoLA)

The Corrector Lens Assembly (CoLA) consist of a spherical-aspherical collimator lens L4 (fused silica) and an adaption ring.

Vibration Test Phase B1

During launch, the lenses have to endure up to 60 times the acceleration due to gravity as well as a cooling to temperatures below -150°C. The vibration test simulates the vibrations encountered during the launch.

Fig. 6. A spherical-aspherical meniscus lens made from CaF2 mounted on a shaker table.

Fig. 6. A spherical-aspherical meniscus lens made from CaF2 mounted on a shaker table.

Movie: Vibration Test 1

Vibration Test Phase B2

Fig. 7. CaF2 lens (improved design)

Fig. 7. CaF2 lens (improved design)

CaF2 lens mounted on a shaker table prepared for vibration test in phase B2.

Movie: Vibration Test 2

Interferometric test setup for lens alignment

For various measurement and adjustment tasks, computer-generated holograms (CGHs) with several zones (MZ-CGHs) are used. These are diffractive optical elements with the ability to form almost arbitrarily shaped wave fronts. The figure shows a setup for a measurement systems analysis of the applied CGHs. For example, the straightness of the axis, defined by the series of spots, is verified with an accuracy in the sub-micron region, which is essential for the lens adjustment.

Fig. 9. Alignment of the scaled lens L2

Fig. 9. Alignment of the scaled lens L2

The scaled lens is aligned with micrometer screws and tightened with clamps.

Optical characterisation of a Multi-Zone-Hologram

Fig. 10.1. Sketch of the MZ-CGH verification setup

Fig. 10.1. Sketch of the MZ-CGH verification setup

Fig. 10.2 The figure shows schematically the zones of a CGH which is used in the project.

Fig. 10.2 The figure shows schematically the zones of a CGH which is used in the project.

Fig. 10.3 Left: Breadboarding of a MZ-CGH in front of an interferometer with a reference sphere installed on a high-precision air-bearing Linear Stage.Right: A MZ-CGH, illuminated with white light, acts as a diffraction grating and decomposes the light into its constituent colours. — Fig. 10.3 Left: Breadboarding of a MZ-CGH in front of an interferometer with a reference sphere installed on a high-precision air-bearing Linear Stage. Right: A MZ-CGH, illuminated with white light, acts as a diffraction grating and decomposes the light into its constituent colours.

Fig. 10.3 Left: Breadboarding of a MZ-CGH in front of an interferometer with a reference sphere installed on a high-precision air-bearing Linear Stage.
Right: A MZ-CGH, illuminated with white light, acts as a diffraction grating and decomposes the light into its constituent colours.

Fig. 10.4 Spot (point-spread-function) of the zone number 3 (see Fig. 10.2) of the MZ-CGH; logarithmic pseudo-colours. Left: Simulation, right: Measurement (camera image). The complex diffraction pattern arises due the particular shape of the aperture stop.

© MPE

Fig. 10.4 Spot (point-spread-function) of the zone number 3 (see Fig. 10.2) of the MZ-CGH; logarithmic pseudo-colours. Left: Simulation, right: Measurement (camera image). The complex diffraction pattern arises due the particular shape of the aperture stop.

© MPE

Test Cryostat for NISP

Fig. 11.1. Sectional view of the cryostat with optical path
Fig. 11.2. Cryostat (opened)
Fig. 11.3. Cryostat (closed, in vertical configuration) — Fig. 11.1. Sectional view of the cryostat with optical path Fig. 11.2. Cryostat (opened) Fig. 11.3. Cryostat (closed, in vertical configuration)

Fig. 11.1. Sectional view of the cryostat with optical path

Fig. 11.2. Cryostat (opened)
Fig. 11.3. Cryostat (closed, in vertical configuration)

The cryostat, cooled by liquid nitrogen, is intended for interferometric testing of the optical design of the NISP instrument. In particular, optical components and detectors operating in the infrared range, are to be tested. For the tests, the components must be cooled to temperatures of about 77 K (-196 ° C). Generally, there are two configurations in which the measurements are to be performed. Firstly, a design wherein the optic and the detection unit are located within the cryostat (and the detection unit is also cooled) and on the other hand, a structure in which the detector unit is located outside the cryostat.

Glass sample irridation proton test

Degradation of optical materials under high energy irradiation – such as loss in transmission – has been observed in the past. Therefore, radiation hardness of glasses and optics materials is required for satellite-born instruments sensitive to a faint loss in transmission.

The proton test was intended to investigate irradiation effects in optics materials, which are foreseen to be used in the Euclid NISP instrument. The test has provided information, how the optical transmission from 500 to 900 nm and in the NIR wavelength range from 900 nm to 2030 nm is affected under the expected total dose during 6.25 years of operation.