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  • 1
    Language: English
    In: Physical review letters, 08 December 2017, Vol.119(23), pp.231101
    Description: According to the weak equivalence principle, all bodies should fall at the same rate in a gravitational field. The MICROSCOPE satellite, launched in April 2016, aims to test its validity at the 10^{-15} precision level, by measuring the force required to maintain two test masses (of titanium and platinum alloys) exactly in the same orbit. A nonvanishing result would correspond to a violation of the equivalence principle, or to the discovery of a new long-range force. Analysis of the first data gives δ(Ti,Pt)=[-1±9(stat)±9(syst)]×10^{-15} (1σ statistical uncertainty) for the titanium-platinum Eötvös parameter characterizing the relative difference in their free-fall accelerations.
    Keywords: Astrophysics - Instrumentation And Methods For Astrophysics ; Astrophysics - Cosmology And Nongalactic Astrophysics ; General Relativity And Quantum Cosmology;
    ISSN: 00319007
    E-ISSN: 1079-7114
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  • 2
    Language: English
    In: 12 July 2018, Vol.10698, pp.1069837-1069837-9
    Description: In the frame work of the ESA Euclid mission to be launched in 2021, the Euclid Consortium is developing an extremely large and stable focal plane for the VIS instrument. After an extensive phase of definition and study over 4 years made at CEA on the thermo-mechanical architecture of that Focal Plane, the first model (Structural and Thermal Model) has been assembled qualified and delivered to MSSL in June 2017. The VIS Focal Plane Assembly integrates 36 CCDs (operated at 153K) connected to their front end electronics (operated at 280K). This Focal Plane will be the largest focal plane (∼0.6 billion pixels) ever built for space application after the GAIA one. The CCDs are CCD-273 type specially designed and provided by the Teledyne e2v company under ESA contract. The Structural and Thermal Model is fully representative of the Flight Model regarding the thermo-mechanical architecture. The STM FPA thus integrates 36 CCDs representative of the flight model except for the detection function. We have implemented specific equipment in order to perform the metrology of the full FPA. It consists of the measurement of the flatness of the full camera as well as the determination of the position of its 36 CCDs. The purpose is to measure the dimension of the sensitive area and to localize each CCDs’ image area with an uncertainty of +/-50 µm in X- and Y-directions. These positions are then given at room temperature in the reference frame of the main FPA structure that is interfaced with the Euclid telescope. The metrology also implies the verification of the flatness of the focal plane in the range of +/-60 μm with an uncertainty of +/-10 μm. Indeed, we must check that the design and the assembly of the FPA meet this requirement that consists of considering that the full photosensitive area is included in a volume of 120 μm high. Based on a marble with a flatness of 10 μm and two motorized linear stages, the test bench combines a CCD camera and a confocal sensor. The camera allows localizing the four fiducial crosses of each CCD-273 and thus to define a grid of 9 equally spaced points on the image area. We can then measure thanks to the confocal sensor the flatness of the full sensitive area in 324 points across the FPA. In this paper, we describe the test bench and the method that we have validated for the STM program. We thus report the results for the STM FPA5 with an estimation of the uncertainty of +/-10 µm for the flatness measurement and around +/- 24 μm (including a coverage factor of 2 for a level of confidence of 95%) for the relative position of the CCDs, which corresponds to twice the pixel size of the CCDs. We finally indicate the improvement that we plan to implement to better estimate the CCDs' position in the FPA coordinates.
    Keywords: Engineering
    ISBN: 9781510619494
    ISBN: 1510619496
    ISSN: 0277786X
    E-ISSN: 1996756X
    Source: SPIE Digital Library - Journals
    Source: SPIE Digital Library - Proceedings
    Source: SPIE Digital Library - eBooks
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  • 3
    Language: English
    In: 06 September 2017, Vol.10378, pp.1037805-1037805-20
    Description: In the frame of EUCLID project, the Calibration Unit of the VIS (VISible Imager) instrument must provide an accurate and well characterized light source for in-flight instrument calibration without noise when it is switched off. The Calibration Unit consists of a set of LEDs emitting at various wavelengths in the visible towards an integrating sphere. The sphere’s output provides a uniform illumination over the entire focal plane. Nine references of LEDs from different manufacturers were selected, screened and qualified under cryogenic conditions. Testing this large quantity of samples led to the implementation of automated testing equipment with complete in-situ monitoring of optoelectronic parameters as well as temperature and vacuum values. All the electrical and optical parameters of the LED have been monitored and recorded at ambient and cryogenic temperatures. These results have been compiled in order to show the total deviation of the LED electrical and electro-optical properties in the whole mission and to select the best suitable LED references for the mission. This qualification has demonstrated the robustness of COTS LEDs to operate at low cryogenic temperatures and in the space environment. Then 6 wavelengths were selected and submitted to an EMC sensitivity test at room and cold temperature by counting the number of photons when LEDs drivers are OFF. Characterizations were conducted in the full frequency spectrum in order to implement solutions at system level to suppress the emission of photons when the LED drivers are OFF. LEDs impedance was also characterized at room temperature and cold temperature.
    Keywords: Engineering
    ISBN: 9781510612136
    ISBN: 1510612130
    ISSN: 0277786X
    E-ISSN: 1996756X
    Source: SPIE Digital Library - Proceedings
    Source: SPIE Digital Library - Journals
    Source: SPIE Digital Library - eBooks
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  • 4
    Language: English
    In: Classical and Quantum Gravity, 2019, Vol.36(22), p.225006 (34pp)
    Description: The weak equivalence principle (WEP), stating that two bodies of different compositions and/or mass fall at the same rate in a gravitational field (universality of free fall), is at the very foundation of general relativity. The MICROSCOPE mission aims to test its validity to a precision of 10 −15...
    Keywords: Physics ; General Relativity and Quantum Cosmology ; Physics ; Mathematics;
    ISSN: 0264-9381
    E-ISSN: 1361-6382
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  • 5
    Description: The Weak Equivalence Principle (WEP), stating that two bodies of different compositions and/or mass fall at the same rate in a gravitational field (universality of free fall), is at the very foundation of General Relativity. The MICROSCOPE mission aims to test its validity to a precision of $10^{-15}$, two orders of magnitude better than current on-ground tests, by using two masses of different compositions (titanium and platinum alloys) on a quasi-circular trajectory around the Earth. This is realised by measuring the accelerations inferred from the forces required to maintain the two masses exactly in the same orbit. Any significant difference between the measured accelerations, occurring at a defined frequency, would correspond to the detection of a violation of the WEP, or to the discovery of a tiny new type of force added to gravity. MICROSCOPE's first results show no hint for such a difference, expressed in terms of E\"otv\"os parameter $\delta(Ti,Pt)=[-1\pm{}9{\rm (stat)}\pm{}9{\rm (syst)}] \times{}10^{-15}$ (both 1$\sigma$ uncertainties) for a titanium and platinum pair of materials. This result was obtained on a session with 120 orbital revolutions representing 7\% of the current available data acquired during the whole mission. The quadratic combination of 1$\sigma$ uncertainties leads to a current limit on $\delta$ of about $1.3\times{}10^{-14}$. Comment: To appear in CQG
    Keywords: General Relativity And Quantum Cosmology ; Astrophysics - Instrumentation And Methods For Astrophysics ; Physics - Space Physics
    Source: Cornell University
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