The detector control unit of the fine guidance sensor instrument on-board the ARIEL mission: design status

ARIEL is an ESA mission whose scientific goal is to investigate exoplanetary atmospheres. The payload is composed by two instruments: AIRS (ARIEL IR Spectrometer) and FGS (Fine Guidance System). The FGS detection chain is composed by two HgCdTe detectors and by the cold Front End Electronics (SIDECAR), kept at cryogenic temperatures, interfacing with the F-DCU (FGS Detector Control Unit) boards that we will describe thoroughly in this paper. The F-DCU are situated in the warm side of the payload in a box called FCU (FGS Control Unit) and contribute to the FGS VIS/NIR imaging and NIR spectroscopy. The F-DCU performs several tasks: drives the detectors, processes science data and housekeeping telemetries, manages the commands exchange between the FGS/DPU (Data Processing Unit) and the SIDECARs and provides high quality voltages to the detectors. This paper reports the F-DCU status, describing its architecture, the operation and the activities, past and future necessary for its development

The instrument control unit of the ARIEL payload: design evolution following the unit and payload subsystems SRR (system requirements review)

ARIEL (Atmospheric Remote-sensing InfraRed Large-survey) is a medium-class mission of the European Space Agency, part of the Cosmic Vision program, whose launch is foreseen by early 2029. ARIEL aims to study the composition of exoplanet atmospheres, their formation and evolution. The ARIEL’s target will be a sample of about 1000 planets observed with one or more of the following methods: transit, eclipse and phase-curve spectroscopy, at both visible and infrared wavelengths simultaneously. The scientific payload is composed by a reflective telescope having a 1m-class elliptical primary mirror, built in solid Aluminium, and two focal-plane instruments: FGS and AIRS. FGS (Fine Guidance System)1 has the double purpose, as suggested by its name, of performing photometry (0.50-0.55 µm) and low resolution spectrometry over three bands (from 0.8 to 1.95 µm) and, simultaneously, to provide data to the spacecraft AOCS (Attitude and Orbit Control System) with a cadence of 10 Hz and contributing to reach a 0.02 arcsec pointing accuracy for bright targets. AIRS (ARIEL InfraRed Spectrometer) instrument will perform IR spectrometry in two wavelength ranges: between 1.95 and 3.9 µm (with a spectral resolution R > 100) and between 3.9 and 7.8 µm with a spectral resolution R > 30. This paper provides the status of the ICU (Instrument Control Unit), an electronic box whose purpose is to command and supply power to AIRS (as well as acquire science data from its two channels) and to command and control the TCU (Telescope Control Unit)

FEA testing the pre-flight Ariel primary mirror

Ariel (Atmospheric Remote-sensing Infrared Exoplanet Large-survey) is an ESA M class mission aimed at the study of exoplanets. The satellite will orbit in the lagrangian point L2 and will survey a sample of 1000 exoplanets simultaneously in visible and infrared wavelengths. The challenging scientific goal of Ariel implies unprecedented engineering efforts to satisfy the severe requirements coming from the science in terms of accuracy. The most important specification – an all-Aluminum telescope – requires very accurate design of the primary mirror (M1), a novel, off-set paraboloid honeycomb mirror with ribs, edge, and reflective surface. To validate such a mirror, some tests were carried out on a prototype – namely Pathfinder Telescope Mirror (PTM) – built specifically for this purpose. These tests, carried out at the Centre Spatial de Liège in Belgium – revealed an unexpected deformation of the reflecting surface exceeding a peek-to-valley of 1µm. Consequently, the test had to be re-run, to identify systematic errors and correct the setting for future tests on the final prototype M1. To avoid the very expensive procedure of developing a new prototype and testing it both at room and cryogenic temperatures, it was decided to carry out some numerical simulations. These analyses allowed first to recognize and understand the reasoning behind the faults occurred during the testing phase, and later to apply the obtained knowledge to a new M1 design to set a defined guideline for future testing campaigns

Preliminary surface charging analysis of Ariel payload dielectrics in early transfer orbit and L2-relevant space environment

Ariel [1] is the M4 mission of the ESA’s Cosmic Vision Program 2015-2025, whose aim is to characterize by lowresolution transit spectroscopy the atmospheres of over one thousand warm and hot exoplanets orbiting nearby stars. The operational orbit of the spacecraft is baselined as a large amplitude halo orbit around the Sun-Earth L2 Lagrangian point, as it offers the possibility of long uninterrupted observations in a fairly stable radiative and thermo-mechanical environment. A direct escape injection with a single passage through the Earth radiation belts and no eclipses is foreseen. The space environment around Earth and L2 presents significant design challenges to all spacecraft, including the effects of interactions with Sun radiation and charged particles owning to the surrounding plasma environment, potentially leading to dielectrics charging and unwanted electrostatic discharge (ESD) phenomena endangering the Payload operations and its data integrity. Here, we present some preliminary simulations and analyses about the Ariel Payload dielectrics and semiconductors charging along the transfer orbit from launch to L2 include

Lunar Gravitational-Wave Antenna

Monitoring of vibrational eigenmodes of an elastic body excited by gravitational waves was one of the first concepts proposed for the detection of gravitational waves. At laboratory scale, these experiments became known as resonant-bar detectors first developed by Joseph Weber in the 1960s. Due to the dimensions of these bars, the targeted signal frequencies were in the kHz range. Weber also pointed out that monitoring of vibrations of Earth or Moon could reveal gravitational waves in the mHz band. His Lunar Surface Gravimeter experiment deployed on the Moon by the Apollo 17 crew had a technical failure rendering the data useless. In this article, we revisit the idea and propose a Lunar Gravitational-Wave Antenna (LGWA). We find that LGWA could become an important partner observatory for joint observations with the space-borne, laser-interferometric detector LISA, and at the same time contribute an independent science case due to LGWA's unique features. Technical challenges need to be overcome for the deployment of the experiment, and development of inertial vibration sensor technology lays out a future path for this exciting detector concept.Comment: 29 pages, 17 figure

Enabling planetary science across light-years. Ariel Definition Study Report

Ariel, the Atmospheric Remote-sensing Infrared Exoplanet Large-survey, was adopted as the fourth medium-class mission in ESA's Cosmic Vision programme to be launched in 2029. During its 4-year mission, Ariel will study what exoplanets are made of, how they formed and how they evolve, by surveying a diverse sample of about 1000 extrasolar planets, simultaneously in visible and infrared wavelengths. It is the first mission dedicated to measuring the chemical composition and thermal structures of hundreds of transiting exoplanets, enabling planetary science far beyond the boundaries of the Solar System. The payload consists of an off-axis Cassegrain telescope (primary mirror 1100 mm x 730 mm ellipse) and two separate instruments (FGS and AIRS) covering simultaneously 0.5-7.8 micron spectral range. The satellite is best placed into an L2 orbit to maximise the thermal stability and the field of regard. The payload module is passively cooled via a series of V-Groove radiators; the detectors for the AIRS are the only items that require active cooling via an active Ne JT cooler. The Ariel payload is developed by a consortium of more than 50 institutes from 16 ESA countries, which include the UK, France, Italy, Belgium, Poland, Spain, Austria, Denmark, Ireland, Portugal, Czech Republic, Hungary, the Netherlands, Sweden, Norway, Estonia, and a NASA contribution

Through the Woods and Underground: Italo Calvino between Ecology and Folklore

This dissertation offers an ecocritical reading of Italo Calvino’s Fiabe italiane, a collection of traditional oral tales published by Einaudi in 1956, and argues that the two-hundred folktales function as a repository of ecological motifs, showing the relationship between humans and the environment as not necessarily exploitative, but rather as a relationship of coexistence and entanglement. The dissertation shows that the critical language that Calvino uses, influenced by a long tradition of folklore studies, rests on two key metaphors to express belonging in a political and national community: rootedness and groundedness. Through the reading of several tales, I show that the folktales themselves actually reveal a fabulist ecology concerned much more with entanglement and enmeshment with the natural landscape, and offer imaginative tools to recover, at the time of the Anthropocene, an enchanted view of the environment. In the first chapter, I argue that the morphology of the folktale that Calvino draws from the Russian formalist Vladimir Propp rests on a conception of the folktale as a plant that can be dissected with the same tools used by a botanist. I show how observations that Calvino makes about tales of metamorphosis of women into plants betray an investment in rootedness as a metaphor for belonging in a political and national community. Drawing from material ecocriticism, I argue that plants, rather than signposts for stasis and belonging, can be read as signs of mixture, coexistence, and symbiosis with the environment. I also argue that the frequent metamorphosis of female characters into plants points toward a trans-corporeal conception of subjectivity. In the second chapter, I show how Calvino contradictorily engages with the legacy of the Brothers Grimm, for whom the forest stands as a metaphor of the lost unity of the German nation. Through a close reading of “Hansel and Gretel,” and Calvino’s rewriting of this tale, “Pulcino,” I show that forests, be they material or fictional, can also be read as environments that preserve an agrarian ecology of subsistence, populated by othered figures such as witches and ogres that depend on a non-exploitative relationship with the environment of the forest. This ecology is preserved in Calvino’s own Marcovaldo, a collection of modern urban fairy-tales that he authored in the same period. Ultimately, I conceive of trees as markers of deep time and connectors between human and geological history. In the third chapter, I turn to the second metaphor identified by my project, groundedness. I briefly reconstruct the cultural milieu in which Calvino operated, and the development of postwar folklore studies after the publication of Antonio Gramsci’s Quaderni del carcere. Therefore, I examine the “Observations on Folklore,” showing how much of Gramsci’s theoretical language engages metaphorically with geology. Calvino himself is indebted to this idea of stratification. His folktales, especially “Cola Pesce,” then become a site where human history and geologic time intersect, and many stories function as repositories of folk knowledge about the telluric landscape of Southern Italy and about the porosity of humans and stones. In the conclusion, I offer an overview of the material and I consider Calvino’s revisiting, in the 1970s, of his earlier folkloric work and how his thoughts on storytelling and belonging evolve in the course of two decade, arguing that they constitute a literary ecology

The shadow position sensors (SPS) metrology subsystem on-board PROBA-3 mission: Design and performance

editorial reviewedPROBA-3 is a two-spacecraft ESA mission carrying the space-based diluted coronagraph ASPIICS. The imaging instrument is hosted on the first spacecraft with the second acting as external occulter. In order to accomplish the payload's scientific tasks, PROBA-3 will ensure sub-millimeter reciprocal positioning of its two satellites by means of closedloop on-board metrology. The Shadow Position Sensors (SPS) sense the penumbra around the instrument aperture and return the 3-D displacement of the coronagraph satellite with respect to its nominal position by running a dedicated algorithm. In this paper we describe how the SPS works and the choices made in order to accomplish the mission objectives