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Calibration Unit (CU) for the VIS instrument of EUCLID mission

Euclid is an ESA mission to map the geometry of the Dark Universe.  The mission will investigate the distance-redshift relationship and the evolution of cosmic structures by measuring shapes and redshifts of galaxies and clusters of galaxies out to redshifts ~2, or equivalently to a look-back time of 10 billion years. In this way, Euclid will cover the entire period over which dark energy played a significant role in accelerating the expansion.

IAS is in charge of procuring the calibration unit for the VIS instrument. The consortium for the manufacturing of VIS is led by MSSL, UK :

The function of the CU is to produce a uniform optical beam in order to perform flatflieds of the VIS FPA in different wavelengths during the length of the mission.

The CU will be operating at cryogenic temperatures close to 150 K.

The CU is composed of an integrated sphere mounted on a foot, its light source is a set of 6 differents LED. The wavelengths cover a range from 590 nm to 890 nm. The optical beam  is defined by a rectangular mask and an aspherical lens. The image of the mask covers the whole FPA (30,3cm x 33,6 cm), the optical flux decreases rapidly outside of this area to minimize straylight in the intrument.

The LED are off the shelf components that were space qualified by CNES with collaboration from Adveotec and IAS.

The Electrical Model (EM) and structural and Thermal Model (STM) of the CU have been delivered to MSSL.

The Qualification Model  (QM) has been developped and tested at IAS.

The Flight Model (FM) has been manufactured and is currently tested for acceptance at IAS.

The FM delivery is expected in december 2018.

The Launch of the Euclid mission is currently scheduled for July 2021.





Fig 1: CAD model of the Euclid payload showing the VIS instrument and the location of the CU



Fig 2: Different views of the CU


Manufacturer Reference Wavelength (nm) Diameter (mm) Chip Optical power (mW) typical current (mA)
Epitex L590-09 590 (571) 4.7 InGaAIP 4 20
Epitex L610-01 610 (594) 5.8 AIInGaP 1,7 20
Optrans VSC644M3A 644 (637) 3 InGaAIP 4 20
Epitex L720-02AU 720 (692) 5.8 AlGaAs 13 50
Epigap EOLD-880-525 880 (834) 5.75 AlGaAs 11 20
Optrans LSC890M3A 890 (850) 3 AlGaAs 4 20


Tab 1: Lists of the LEDs and their main characteristics



Fig 3: LED spectrums at Top =146K



Fig 4: CU STM during vibration tests at IAS calibration facility




Fig 5: CU QM with LED 720 nm ON




Fig 6: CU QM, LED 720 ON, rectangular optical beam



Fig 7 : CU FM assembled




small_anne_6607_b.png  Contact : Anne Philippon, project manager for VIS-CU EUCLID at IAS

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