The Ariel space mission will characterize spectroscopically the atmospheres of a large and diverse sample of hundreds of exoplanets. Through the study of targets with a wide range of planetary parameters (mass, density, equilibrium temperature) and host star types the origin for the diversity observed in known exoplanets will be better understood. Ariel is an ESA Medium class science mission (M4) with a spacecraft bus developed by industry under contract to ESA, and a Payload provided by a consortium of national funding agencies in ESA member states, plus contributions from NASA, the CSA and JAXA. The payload is based on a 1-meter class telescope operated at below 60K, built all in Aluminium, which feeds two science instruments. A multi-channel photometer and low-resolution spectrometer instrument (the FGS, Fine Guidance System instrument) operating from 0.5 - 1.95 microns in wavelength provides both guidance information for stabilizing the spacecraft pointing as well as vital scientific information from spectroscopy in the near-infrared and photometry in the visible channels. The Ariel InfraRed Spectrometer (AIRS) instrument provides medium resolution spectroscopy from 1.95 - 7.8 microns wavelength coverage over two instrument channels. Supporting subsystems provide the necessary mechanical, thermal and electronics support to the cryogenic payload. This paper presents the overall picture of the payload for the Ariel mission. The payload tightly integrates the design and analysis of the various payload elements (including for example the integrated STOP analysis of the Telescope and Common Optics) in order to allow the exacting photometric stability requirements for the mission to be met. The Ariel payload has passed through the Preliminary Design Review (completed in Q2 2023) and is now developing and building prototype models of the Telescope, Instruments and Subsystems (details of which will be provided in other contributions to this conference). This paper will present the current status of the development work and outline the future plans to complete the build and verification of the integrated payload.

AIRS is the infrared spectroscopic instrument of ARIEL: Atmospheric Remote-sensing Infrared Exoplanet Large-survey mission adopted in November 2020 as the Cosmic Vision M4 ESA mission and planned to be launched in 2029 by an Ariane 6 from Kourou toward a large amplitude orbit around L2 for a 4-year mission. Within the scientific payload, AIRS will perform transit spectroscopy of over 1000 exoplanets to complete a statistical survey, including gas giants, Neptunes, super-Earths and Earth-size planets around a wide range of host stars. All these collected spectroscopic data will be a major asset to answer the key scientific questions addressed by this mission: what are exoplanets made of? How do planets and planetary systems form? How do planets and their atmospheres evolve over time? The AIRS instrument is based on two independent channels covering 1.95-3.90 mu m (CH0) and 3.90-7.80 mu m (CH1) wavelength ranges with prism-based dispersive elements producing spectra of low resolutions R>100 in CH0 and R>30 in CH1 on two independent detectors. The spectrometer is designed to provide a Nyquist-sampled spectrum in both spatial and spectral directions to limit the sensitivity of measurements to the jitter noise and intra pixels pattern during the long (10 hours) transit spectroscopy exposures. A full instrument overview will be presented covering the thermo-mechanical design of the instrument functioning in a 60 K environment, up to the detection and acquisition chain of both channels based on 2 HgCdTe detectors actively cooled to below 42 K. This overview will present updated information of phase C studies, in particular on the assembly and testing of prototypes that are highly representative of the future engineering model that will be used as an instrument-level qualification model.

This paper focuses on the dedicated accelerometers developed for the MICROSCOPE mission taking into account the specific range of acceleration to be measured on board the satellite. Considering one micro-g and even less as the full range of the instrument with an objective of one femto-g resolution, that leads to a customized concept and a high-performance electronics for the sensing and servo-actuations of the accelerometer test-masses. This range and performance directed the payload development plan. In addition to a very accurate geometrical sensor core, a high performance electronics architecture provides the measurement of the weak electrostatic forces and torques applied to the test-masses. A set of capacitive detectors delivers the position and the attitude of the test-mass with respect to a very steady gold-coated cage made in silica. The voltages applied on the electrodes surrounding each test-mass are finely controlled to generate the adequate electrical field and so the electrostatic pressures on the test-mass. This field maintains the test-mass motionless with respect to the instrument structure. Digital control laws are implemented in order to enable instrument operation flexibility and a weak position detector noise. These electronics provide both the scientific data for MICROSCOPE's test of the weak equivalence principle and the input for the satellite drag-free and attitude control system.

The MICROSCOPE mission was designed to test the Weak Equivalence Principle (WEP), stating the equality between the inertial and the gravitational masses, with a precision of 10^-15 in terms of the Eötvös ratio η. Its experimental test consisted of comparing the accelerations undergone by two collocated test masses of different compositions as they orbited the Earth, by measuring the electrostatic forces required to keep them in equilibrium. This was done with ultra-sensitive differential electrostatic accelerometers onboard a drag-free satellite. The mission lasted two and a half years, cumulating five-months-worth of science free-fall data, two thirds with a pair of test masses of different compositions – Titanium and Platinum alloys – and the last third with a reference pair of test masses of the same composition – Platinum. We summarize the data analysis, with an emphasis on the characterization of the systematic uncertainties due to thermal instabilities and on the correction of short-lived events which could mimic a WEP violation signal. We found no violation of the WEP, with the Eötvös parameter of the Titanium and Platinum pair constrained to η( Ti, Pt) = [-1.5 ± 2.3 (stat)± 1.5 (syst)] × 10^-15 at 1σ in statistical errors.

The space mission MICROSCOPE dedicated to the test of the equivalence principle (EP) operated from April 25, 2016 until the deactivation of the satellite on October 16, 2018. In this analysis we compare the free-fall accelerations (a (A) and a (B)) of two test masses in terms of the Eotvos parameter eta(A,B)=2aA-aBaA+aB <i . No EP violation has been detected for two test masses, made from platinum and titanium alloys, in a sequence of 19 segments lasting from 13 to 198 h down to the limit of the statistical error which is smaller than 10(-14) for eta(Ti, Pt). Accumulating data from all segments leads to eta(Ti, Pt) = [-1.5 +/- 2.3 (stat) +/- 1.5 (syst)] x 10(-15) showing no EP violation at the level of 2.7 x 10(-15) if we combine stochastic and systematic errors quadratically. This represents an improvement of almost two orders of magnitude with respect to the previous best such test performed by the Eot-Wash group. The reliability of this limit has been verified by comparing the free falls of two test masses of the same composition (platinum) leading to a null Eotvos parameter with a statistical uncertainty of 1.1 x 10(-15).

The MICROSCOPE mission aims to test the weak equivalence principle (WEP) in orbit with an unprecedented precision of 10 −15 on the Eötvös parameter thanks to electrostatic accelerometers on board a drag-free micro-satellite. The precision of the test is determined by statistical errors, due to the environment and instrument noises, and by systematic errors to which this paper is devoted. Systematic error sources can be divided into three categories: external perturbations, such as the residual atmospheric drag or the gravity gradient at the satellite altitude, perturbations linked to the satellite design, such as thermal or magnetic perturbations, and perturbations from the instrument internal sources. Each systematic error is evaluated or bounded in order to set a reliable upper bound on the WEP parameter estimation uncertainty.

AIRS is the infrared spectroscopic instrument of ARIEL: Atmospheric Remote‐sensing Infrared Exoplanet Large‐survey mission selected in March 2018 as the Cosmic Vision M4 ESA mission and planned to be launched in 2029 by an Ariane 6 from Kourou toward a large amplitude orbit around L2 for a 4 year mission. Within the scientific payload, AIRS will perform transit spectroscopy of over a 1000 of exoplanets to complete a statistical survey, including gas giants, Neptunes, super-Earths and Earth-size planets around a wide range of host stars. All these collected spectroscopic data will be a major asset to answer the key scientific questions addressed by this mission: what are the exoplanets made of? How do planets and planetary system form? How do planets and their atmospheres evolve over time? The AIRS instrument is based on two independent channels covering the CH0 [1.95-3.90] µm and the CH1 [3.90-7.80] µm wavelength range with prism-based dispersive elements producing spectrum of low resolutions R<100 in CH0 and R<30 in CH1 on two independent detectors. The spectrometer is designed to provide spectrum Nyquist-sampled in both spatial and spectral directions to limit the sensitivity of measurements to the jitter noise and intra pixels pattern during the long (10 hours) transit spectroscopy exposures. A full instrument overview will be presented covering the thermal mechanical design of the instrument functioning in a 60 K cold environment, up to the detection and acquisition chain of both channels based on 2 HgCdTe detectors actively cooled down below 42 K. This overview will present updated information of phase B2 studies in particular with the early manufacturing of prototype for key elements like the optics, focal-plane assembly and read-out electronics as well as the results of testing of the IR detectors up to 8.0 μm cut-off.

Since the MICROSCOPE instrument aims to measure accelerations as low as a few 10−15 m s−2 and cannot operate on ground, it was necessary to have a large time dedicated to its characterization in flight. After its release and first operation, the characterization experiments covered all the aspects of the instrument design in order to consolidate the scientific measurements and the subsequent conclusions drawn from them. Over the course of the mission we validated the servo-control and even updated the PID control laws for each inertial sensor. Thanks to several dedicated experiments and the analysis of the instrument sensitivities, we have been able to identify a number of instrument characteristics such as biases, gold wire and electrostatic stiffnesses, non linearities, couplings and free motion ranges of the test-masses, which may first impact the scientific objective and secondly the analysis of the instrument good operation.

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 Eötvös parameter δ(Ti,Pt)=[-1±9 (stat)±9 (syst)] ×10^-15 (both 1σ 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 1σ uncertainties leads to a current limit on δ of about 1.3×10^-14.

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.

In the frame work of the ESA Euclid mission to be launched in 2020, 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 150K) 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 CCD273 type specially designed and provided by the Teledyne e2v company under ESA contract, front end electronics is studied and provided by MSSL. The Structural and Thermal Model is fully representative of the Flight Model regarding the thermo-mechanical architecture. As the instrument development philosophy follows a Proto Flight approach this choice has been made very early in the development program in order to reduce the risk on the PFM program. So the AIT/AIV plan has been built in order to fully validate since the STM program the overall integration, verification and qualification sequences, taking into account the very stringent cleanliness requirement. The STM FPA integrates 36 CCDs representative of the flight model except for the detection function. Electrical configuration of the front end electronics provides electrical interface in order to power the CCDs and check integrity of all the electrical links to CCDs. In this paper we first recall the architecture of the VIS-FPA and especially the solutions proposed to cope with the scientific needs of an extremely stable focal plane, both mechanically and thermally leading to a SiC structure. The modular architecture concept, considered as a key driver for such big and complex focal plane is detailed. Parallel to that, the integration workflow including verification steps is fully depicted including specific aspects linked to the use of SiC. Validation and qualification test program is described. A summary of geometrical measurements, thermal balance tests and vibrations tests including the main Ground Support Equipment description are reported. Keyword list: Euclid, CCD, SiC, focal plane, architecture, integration

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.

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 non-vanishing 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.

The EUSO-Balloon is a pathfinder of the JEM-EUSO mission, designed to be installed on-board the International Space Station before the end of this decade. The EUSO-Balloon instrument, conceived as a scaleddown version of the main mission, is currently developed as a payload of a stratospheric balloon operated by CNES, and will, most likely, be launched during the CNES flight campaign in 2014. Several key elements of JEM-EUSO have been implemented in the EUSO-Balloon. The instrument consists of an UV telescope, made of three Fresnel lenses, designed to focus the signal of the UV tracks, generated by highly energetic cosmic rays propagating in the earth's atmosphere, onto a finely pixelized UV camera. In this contribution, we review the main stages of the signal processing of the EUSO-Balloon instrument: the photodetection, the analog electronics, the trigger stages, which select events while rejecting random background, the acquisition system performing data storage and the monitoring, which allows the instrument control during operation.