Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital parameters of a planet to the nature of its parent star. We have little idea whether the chemistry of a planet is linked to its formation environment, or whether the type of host star drives the physics and chemistry of the planet's birth, and evolution. ARIEL was conceived to observe a large number (~1000) of transiting planets for statistical understanding, including gas giants, Neptunes, super-Earths and Earth-size planets around a range of host star types using transit spectroscopy in the 1.25-7.8 μm spectral range and multiple narrow-band photometry in the optical. ARIEL will focus on warm and hot planets to take advantage of their well-mixed atmospheres which should show minimal condensation and sequestration of high-Z materials compared to their colder Solar System siblings. Said warm and hot atmospheres are expected to be more representative of the planetary bulk composition. Observations of these warm/hot exoplanets, and in particular of their elemental composition (especially C, O, N, S, Si), will allow the understanding of the early stages of planetary and atmospheric formation during the nebular phase and the following few million years. ARIEL will thus provide a representative picture of the chemical nature of the exoplanets and relate this directly to the type and chemical environment of the host star. ARIEL is designed as a dedicated survey mission for combined-light spectroscopy, capable of observing a large and welldefined planet sample within its 4-year mission lifetime. Transit, eclipse and phasecurve spectroscopy methods, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allow us to measure atmospheric signals from the planet at levels of 10-100 part per million (ppm) relative to the star and, given the bright nature of targets, also allows more sophisticated techniques, such as eclipse mapping, to give a deeper insight into the nature of the atmosphere. These types of observations require a stable payload and satellite platform with broad, instantaneous wavelength coverage to detect many molecular species, probe the thermal structure, identify clouds and monitor the stellar activity. The wavelength range proposed covers all the expected major atmospheric gases from e.g. H 2 O, CO 2 , CH 4 NH 3 , HCN, H 2 S through to the more exotic metallic compounds, such as TiO, VO, and condensed species. Simulations of ARIEL performance in conducting exoplanet surveys have been performedusing conservative estimates of mission performance and a

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ABSTRACT. We describe the layout and unique features of the focal plane system for MIRI. We begin with the detector array and its readout integrated circuit (combining the amplifier unit cells and the multiplexer), the electronics, and the steps by which the data collection is controlled and the output signals are digitized and delivered to the JWST spacecraft electronics system. We then discuss the operation of this MIRI data system, including detector readout patterns, operation of subarrays, and data formats. Finally, we summarize the performance of the system, including remaining anomalies that need to be corrected in the data pipeline.Online material: color figures DETECTOR SYSTEM OVERVIEWThe science potential of the James Webb Space Telescope (JWST) is derived from the rapid advances over the past three decades in performance and size of infrared arrays. Some of the applications are discussed in Gardner et al. (2006). The greatest gains with JWST will be in the deep thermal infrared, where the high backgrounds on the ground have compromised the infrared array performance and previous cooled telescopes in space have had small apertures and limited angular resolution; see Rieke et al. (2014a, hereafter Paper I).To implement fully the deep thermal infrared capabilities of the JWST, the Mid-Infrared Instrument (MIRI) uses three arsenic-doped impurity band conduction detector arrays, each of 1024 × 1024 pixel format with 25 μm pixel pitch. The performance expected is described in Glasse et al. (2014, hereafter Paper IX). These detectors have heritage to the Si:As devices used in all three Spitzer instruments, but particularly to the arrays in the Infrared Array Camera (IRAC) (Fazio et al. 2004;Hora et al. 2004). Like the IRAC arrays, the MIRI devices were manufactured by Raytheon Vision Systems (RVS) in Goleta, California. Both array types use a customized cryogenic readout process to provide stable performance at low temperature, and their detectors are generally similar in terms of doping levels, layer thicknesses, and pixel pitch.The MIRI detector system, or more formally the focal plane system (FPS), is shown as a block diagram in Figure 1. It is composed of three entities: the focal plane modules (FPMs), the focal plane electronics (FPE), and the focal plane harness (FPH). A FPM houses a detector array and locates it at the relevant focal plane provided by the optical assembly (see Figs. 2 and 3). There are three FPMs: one for the imager, and one each for the shortwave and longwave channels in the mediumresolution spectrometer (MRS). The 4 m long FPH carries all electrical signals between the FPMs and the FPE. The FPE consists of the control and readout electronics for the detectors and also monitors and controls the temperature of each FPM to within 10 mK. Each of the FPMs is driven by separate signal chain electronics and temperature control slices, with internal block redundancy (sides A and B). Our discussion of this system begins with FPMs ( § 2) and FPE ( § 3), followed by a description of the ope...

EChO, the Exoplanet Characterisation Observatory, has been one of the five M-class mission candidates competing for the M3 launch slot within the science programme Cosmic Vision 2015-2025 of the European Space Agency (ESA). As such, EChO has been the subject of a Phase 0/A study that involved European Industry, research institutes and universities from ESA member states and that concluded in Exp Astron EChO is a concept for a dedicated mission to measure the chemical composition and structure of hundreds of exoplanet atmospheres using the technique of transit spectroscopy. With simultaneous and uninterrupted spectral coverage from the visible to infrared wavelengths, EChO targets extend from gas giants (Jupiter or Neptune-like) to super-Earths in the very hot to temperate zones of F to M-type host stars, opening up the way to large-scale, comparative planetology that would place our own solar system in the context of other planetary systems in the Milky Way. A review of the performance requirements of the EChO mission was held at ESA at the end of 2013, with the objective of assessing the readiness of the mission to progress to the Phase B1 study phase. No critical issues were identified from a technical perspective, however a number of recommendations were made for future work. Since the mission was not selected for the M3 launch slot, EChO is no longer under study at ESA. In this paper we give an overview of the final mission concept for EChO as of the end of the study, from scientific, technical and operational perspectives.