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Ariel, the “atmospheric remote sensing infrared exoplanet large survey” mission, is the European Space Agency’s Cosmic Vision M4 (medium-class number 4) science mission. It has recently gone through an implementation approval (“adoption”), with a planned launch in 2029. Ariel, together with two other M4 candidate missions (THOR and XIPE), was recommended in June 2015 to enter an assessment study, consisting of a Phase 0 at the ESA internal Concurrent Design Facility study followed by a Phase A with parallel industrial studies. The Phase A was concluded in March 2018 with the selection of Ariel as the M4 mission endorsed by the ESA Science Programme Committee (SPC). Phase B1 was subsequently initiated, and was concluded by the Mission Adoption Review in mid-2020, followed by the formal adoption of Ariel in November 2020 by the SPC. Ariel is a survey-type mission dedicated to the characterisation of exoplanets by performing a chemical census. Using the differential technique of transit/eclipse spectroscopic observations, Ariel will obtain transmission and/or emission spectra of the atmospheres of a large (~1000) and diverse sample of known exoplanets covering a wide range of masses, densities, equilibrium temperatures, orbital properties and host-star characteristics. This will include hot Jupiters to warm Super-Earths, orbiting A to M spectral class host stars. This paper reports on the Ariel Phase 0/A/B1 study, including the conclusions of the reviews that were conducted in 2020 to close the study and support the adoption process.

The Sun–Earth Libration Points (SEL) are an attractive location for many astronomy missions. The transfer towards a libration point orbit requires in many cases an immediate injection, meaning the launch system accelerates the spacecraft into its desired transfer orbit. The limited number of available launcher programs and the launcher dispersion then require a time-critical correction manoeuvre in order to deliver the spacecraft to its intended orbit. This manoeuvre can only be performed after the state of the spacecraft has been determined in a tracking campaign and usually takes place one to two days into the mission. The drawbacks of this strategy are on the one hand the increased Δ V requirement, since a tangential perigee velocity error has by then been amplified by a factor of approximately eight, and on the other hand, the risk of not being able to perform the manoeuvre at day two, further increasing the Δ V requirements or even losing the mission due to the limited thrust capability. This study investigates a strategy to mitigate the criticality of the first correction manoeuvre: the utilization of an intermediate highly elliptical parking orbit (HEO). The goal of this strategy is to increase the robustness of the mission design and to ease the spacecraft operation after launch. While the risk mitigation of the first mission critical manoeuvre is the primary motivation for this study there is also potential for increasing the payload mass due to the staging effect. The paper will first discuss general requirements for the transfer and two examples for missions going to a small amplitude Lissajous and a large Quasi-Halo orbit will be used to demonstrate the indirect transfer option.

The Astronautics and Space Station Department of the Universitaet Stuttgart has developed a design environment for the conceptual design of manned space missions. With the assistance of the ESA European Space Operations Center this design environment has been extended to cover exploration missions involving the areas of the collinear Earth–Moon and Sun–Earth libration points, which are of interest as an alternative staging location to the low lunar orbit approach for lunar exploration and for satellite servicing missions, respectively. To allow for a reliable mission design, the transfer times, the Δ V and variations in the Δ V for transfers between the different locations in the Sun–Earth–Moon system must be known, especially taking the rendezvous constraints and safety issues for human spaceflight missions into account. The results of the investigations presented in this paper cover transfer trajectories from Earth to different types of orbits about the collinear Earth–Moon libration points 1 and 2 and further on to the Moon. For the Earth to Earth–Moon libration point transfer, direct trajectories, fly-bys at the Moon and trajectories via the weak stability boundary region of the Sun–Earth system are treated.

Several approaches are used at JET to achieve operation at high density with good energy confinement. One of them is the injection of solid fuel pellets to realize efficient particle refuelling by deposition deep inside the plasma column. The new pellet launch system capable of launching from the torus magnetic high field side was investigated for its capability to fulfil this task in conventional ELMy H-mode discharges. Optimized pellet scenarios were developed for plasma configurations with IP = 2.5 MA, Bt = 2.4 T, averaged triangularity � δ �≈ 0.34 and mainly neutral beam heating at a level of approximately 17 MW. The accessible operational range was extended by the pellet tool with respect to gas puff refuelling. For example, H-mode conditions could be maintained at densities beyond the Greenwald level. Plasma energy confinement was observed to become density independent at high densities. When avoiding confinement deterioration due to pellet triggered MHD activity or parasitic pellet born gas in appropriate pulse schedules, enhanced particle inventory with more peaked density profiles was achieved while maintaining the plasma

We prepared multilayer taped from (Tl,Pb)-1223 thick films electrophoretically deposited on silver tapes. A multilayer tape was rolled in the transverse direction, pressed and sintered. The transport current was 33 A at 77 K and 80 A at 30 K, corresponding to a critical current density of about at 77 K. In a magnetic field of 0.1 T the critical current density decreased by a factor of 20 and remained nearly constant at higher fields. The critical current density derived from magnetization data was at 10 K and at 77 K.

We prepared superconducting samples of the 1212 systems (Pb0.5Sr0.5)Sr2(Y1-xCax)Cu2O7+or- delta and (Pb0.5Ca0.5)Sr2(Y1-xCax)Cu2O7+or- delta in an oxidizing atmosphere of normal O2 pressure. By variation of the Y/Ca ratio an optimum of the temperature at which superconductivity sets in, Tcons, was found for x=0.80 in both systems. X-ray diffraction studies give evidence that the range of stability of the 1212 structure with respect to x is slightly greater in the (Pb,Ca) system than in the (Pb,Sr) system. We observed an increase of the lattice constants with x, suggesting that structural stress increases with Ca content. The loss of weakly bound O after post-annealing and quenching the samples in liquid N2 improves the normal state conductivity and increases Tcons and also TcR=0 for most of the samples.

(Bi,Pb)-2223 wires were fabricated by electrophoretic co-deposition of , CaO and PbO powders on thin silver fibres. A non-stoichiometric mixture was used during deposition to obtain an optimum amount of 2223 phase after sintering. The transition temperature of the wires was 110 K and the critical current density, derived from magnetization data, was about at 10 K.

We performed a detailed study of the emission spectra of a hot-hole cyclotron p-germanium laser. The laser was operated in crossed electric and magnetic fields, which were parallel to two different (110) axes of the germanium crystal. Using a high-resolution Fabry-Perot spectrometer a broadening of the laser line was found. A band structure analysis made it possible to understand the observed feature. The line broadening is explained by the inhomogeneity of the electric field inside the crystal, which leads to slight deviations of the resonance frequency in different places. We manufactured a non-rectangular shaped laser crystal for enhancing the electric field homogeneity. Our first results show that the new laser configuration leads to a narrowing of the laser line.

We report on the study of the submillimeter absorptivity of high‐Tc superconductors by a new method, the photothermal interference spectroscopy. Absorption in a sample leads to a temperature change of the sample and, by heat transfer, also of a gas volume adjacent to the sample and to a change of refractive index in the gas volume that we detect by an interferometric method. We demonstrate the feasibility of the method by determination of the absorptivity of high‐Tc superconducting YBa2Cu3O7−δ samples for submillimeter radiation at a frequency near 1 THz. The absorptivity shows a peak at Tc, that is most likely due to fluctuation effects, a strong drop below Tc and a finite value at low temperatures, with a peak near 15 K.

A laser system composed of a grating tuned high-pressure CO2-laser pumping a single-pass molecular gas laser is demonstrated to deliver high intense coherent light pulses covering the spectral range of the mid- and far-infrared. The transversal electrically excited CO2-laser emitts radiation pulses of up to 300 ns length and powers up to several MW; using mode-locking techniques single nanosecond radiation pulses can be obtained. Using the CO2-laser radiation for optical pumping of appropriate molecular gases, frequency tenability can be transferred into the far-infrared via Raman tuning. Highest efficiencies up to quantum conversion rates exceeding 0.1 have been found for several isotopes of the methylhalides (CH3X; X = F, Cl, Br, J), heavy water (D2O) and ammonia (NH3). For these gases, more than a thousand Raman tuning regions are available ranging from the spectral region of millimeter waves to wavelength of 40 μm. Pulse durations below 100 ps can be achieved when mode-locking techniques are applied at the pump laser. The laser system has already been used for numerous spectroscopic applications.

Far-infrared applications of high temperature superconductors, namely Fabry-Perot resonators and fast detectors, are reported. At terahertz frequencies high finesse (~ 60 at 3 THz) is obtained for Fabry-Perot resonators with YBa2Cu3O7-on-MgO reflectors and fast, nonbolometric response with a response time < 100 ps is found for structured YBa2Cu3O7 thin films at frequencies from 0.1 THz to nearly 10 THz.

Results of direct absorptivity measurements at ω=0.89 THz of thin films belonging to three different families of HTc compounds are reported. In all samples a significant decrease of absorption below T, with nonzero values at T<

Reflexion von Infrarot-Strahlung an normalleitenden Metallschichten ist immer mit Absorption verbunden. Metallschichten sind daher zum Einsatz in Fabry-Perot-Interferometern fur THz-Strahlung nicht geeignet. Bislang werden stattdessen feinmaschige Metallnetze als Reflektoren verwendet. Diesen erwachst neuerdings Konkurrenz durch Resonatoren auf der Basis von dunnen Schichten aus Hochtemperatur-Supraleitern.

The shape of a horizontal meniscus which is influenced both by capillarity and by an adsorbed thin film is determined. An exact solution is obtained which clearly shows the features of a transition between a curved meniscus and an adsorbed film. The method of matched asymptotic expansions is used to elucidate many of the details of the transition layer, its horizontal thickness, and the question of apparent contact angle.

In this paper new methods for generation and detection of terahertz-phonons and application of these methods for a study of dynamical properties of high-frequency acoustic phonons in a crystal at low temperature are discussed. Terahertz-phonons are generated via multiphonon absorption by use of pulsed infrared radiation. For phonon detection phonon-induced fluorescence is observed. We have investigated the anharmonic decay of acoustic phonons. The experimental results indicate that the decay of acoustic phonons in the linear part of the dispersion curves can be described by a phonon decay cascade that can be characterized by a shape function. The optical techniques allow also to study for tetrahertz-phonons elastic scattering at impurities and the behaviour at crystal surfaces. We will, finally, discuss the role of the dynamics of tetrahertz-phonons for particle detection via phonons.

Am Modell der linearen zweiatomigen Kette aus geladenen Teilchen wird die Wirkung eines in einen Kristall periodisch eingebauten Defektes diskutiert. Insbesondere werden die Lage der Eigenfrequenzen des gestorten Gitters und die Defekt-induzierte optische Absorption durch Band- und lokalisierte Schwingungen diskutiert. Fern-Infrarot-Messungen an KJ, das mit Molekulen dotiert ist, liefern folgende Ergebnisse: 1. In KJ:NO 2 − und in KJ:OH− tritt eine induzierte Bandabsorption auf, die denselben spektralen Verlauf hat wie die Dichte der Gitterschwingungen des reinen Kristalls. 2. In der Phononenbandlucke von KJ treten zahlreiche Linien auf mit Halbwertsbreiten ≦ 0,4 cm−1. Die beobachteten Linien konnen auser lokalisierten Translationsschwingungen auch Librationsmodes der Molekule entsprechen, eine eindeutige Zuordnung kann nicht gegeben werden.

A new method for tunable detection and generation of terahertz phonons is reported. It is based on our observation that the lowest energy level of excited Eu2+ ions in CaF2 and SrF2 crystals can be split by uniaxial stress into two levels with a variable separation up to 2.4 THz. Phonons are generated by one‐phonon relaxation between these levels and detected by phonon‐induced fluorescence radiation from the upper level. The detector is applied to study the spectral distribution of phonons generated by the heat‐pulse technique.

Thermal wave transmission probing is used for nondestructive remote subsurface flaw detection in metal. It is shown that depth information of subsurface structure is obtained when two thermal wave sources are operated simultaneously in a stereoscopic arrangement.

A new technique for the monochromatic detection of ${10}^{12}$-Hz phonons is applied to the study of 20-${\mathrm{cm}}^{\ensuremath{-}1}$ phonons in ruby. The resolution of the phonon detector in space and time allows the observation of the local imprisonment of 29-${\mathrm{cm}}^{\ensuremath{-}1}$ phonons in a ruby crystal that contains variable concentrations of ${\mathrm{Cr}}^{3+}$ ions in the excited $\overline{E}(^{2}E)$ state. The application for the determination of the lifetime of ${10}^{12}$-Hz phonons is discussed.

Experiments with monochromatically generated phonons in Al2O3 are reported. We found that the lifetime of phonons, trapped in a ruby crystal because of resonance scattering at excited Cr3+ ions, is strongly reduced after X-ray irradiation of the crystal indicating inelastic scattering at impurity ions generated by the X irradiation. Furthermore, direct observation of inelastic scattering of phonons, trapped in Al2O3 because of resonance scattering at V4+ ions, is reported.

We have performed measurements and calculations of spontaneous lifetimes of acoustic phonons in diamond.

Recently developed far infrared techniques of phonon generation and detection are discussed. Detection was performed by far infrared phonon-difference absorption; the method was applied to determine lifetimes of zone-boundary phonons in TlCl and TlBr crystals at different crystal temperatures. Phonon generation was performed by multiphonon infrared absorption; it was found that an originally broadband phonon spectrum narrowed with increasing time after pulsed excitation. Extremely monochromatic phonons were generated by far infrared excitation and relaxation of electronic impurity states; the far infrared generation was applied, together with monochromatic optical detection, to study bottleneck effects for phonons in Al2O3 crystals that contained either excited Cr3+ ions or V4+ ions.

A new method of high-frequency phonon detection is reported. By time-resolved far-infrared spectroscopy, transverse acoustic zone-boundary phonons in TlCl and TlBr crystals are observed and the decay of these phonons at temperatures from 3 K to 20 K is investigated.

The lowest excited electronic state 4f65d (Γ 8 + ) of Eu2+ ions in CaF2 and SrF2 can be split in two sublevels by applying uniaxial stress along the [001] crystalline axis.1 This splitting is used for phonon detection up to a frequency of 2.4 THz. The phonons are detected by phonon-induced fluorescence radiation due to their resonance interaction with the stress-split sublevels.