Publication archive

Publication archive

Reference: ESA-SPI-EST-MIS-RP-001

SPICA (SPace Infrared telescope for Cosmology and Astrophysics) is a far IR telescope to study and answer fundamental astrophysical questions ranging from the formation and evolution of galaxies to the physics of star formation in dusty environments, including the role of magnetic fields, and the origin of planetary systems.

The SPICA mission was conceived as a cooperation between ESA and JAXA and it was initially selected as a candidate for the Cosmic Vision M5 mission together with THESEUS and EnVision. In the course of Phase A, it appeared that, although technical feasibility could be demonstrated, SPICA cost at completion was exceeding the boundaries of an M-class mission. Therefore, ESA, JAXA and SRON jointly decided to withdraw the mission from the M5 selection.

However, the Phase A was completed. The technical outcome is documented in the following report which may be used as guidance and reference for future studies.

Published: 12 July 2021

Reference: ESA/SCI(2021)2

This is the Assessment Study Report (also known as the Yellow Book) for THESEUS (Transient High-Energy Sky and Early Universe Surveyor) - a candidate mission for the M5 launch opportunity in Cosmic Vision.

THESEUS is designed to fully exploit the unique and breakthrough potentialities of Gamma-Ray Bursts for investigating the Early Universe and advancing multi-messenger astrophysics, while simultaneously vastly increasing the discovery space of high energy transient phenomena over the entirety of cosmic history.

Published: 18 February 2021

Reference: ESA/SCI(2021)1

This is the Assessment Study Report (also known as the Yellow Book) for EnVision - a candidate mission for the M5 launch opportunity in Cosmic Vision.

EnVision is a Venus orbiter mission that will determine the nature and current state of Venus' geological evolution and its relationship with the atmosphere, to understand how and why Venus and Earth evolved so differently.

Published: 18 February 2021

Reference: ESA/SCI(2020)1

This definition study report, or Red Book, presents a summary of the very large body of work that has been undertaken on the Ariel mission over the 30-month period of the Ariel definition phase.

Ariel, the Atmospheric Remote-sensing Infrared Exoplanet Large-survey, is the fourth medium-class mission in ESA's Cosmic Vision programme. It will address the fundamental questions on what exoplanets are made of and how planetary systems form and evolve by investigating the atmospheres of many hundreds of diverse planets orbiting different types of stars.

Published: 12 November 2020
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This brochure summarises the Planck mission and gives a glimpse of its main achievements.

Planck set out to map the very faint anisotropies in the Cosmic Microwave Background to an angular resolution and sensitivity that would exhaust all the cosmological information that can be extracted from them. In addition Planck has mapped the much fainter polarised fraction of these same anisotropies. The resulting maps of the sky contain traces from the very earliest times, revealing the recipe that embodies our most precise understanding of the structure, composition, and evolution of the Universe that we inhabit.


  • Foreword
  • Making sense of the Universe
  • The early Universe
  • The Planck mission
  • An almost perfect Universe
  • Planck's view of the Cosmic Microwave Background
  • The big and the small
  • Structure formation and gravitational lensing
  • The first stars
  • Mapping foreground emission from the Milky Way
  • A lasting legacy


Published: 11 November 2020

This document presents the activities in the Science Core Technology Programme (CTP) and in the Technology Development Element (TDE, replacing the TRP) of the Discovery, Preparation & Technology Development Basic Activities supporting the implementation of ESA's Science Programme. The national initiatives activities of relevance to the Science programme are provided for information. Activities funded through the Industrial Policy Task Forces (IPTFs) and of relevance to the Science Programme are also provided for information.

This document is provided for information only and is subject to future updates.

Published: 30 June 2023

Download this interactive media kit to learn more about the launch of Solar Orbiter in February 2020 and the science goals of the mission. Solar Orbiter will perform unprecedented close-up observations of the Sun and from high-latitudes, providing the first images of the uncharted polar regions of the Sun, and investigating the Sun-Earth connection.


  • Introduction
  • How to use this media kit
  • Event programme
  • How to follow the launch online
  • What’s new
  • Answering the big questions
  • Operating in extreme environments
  • Instruments
  • Launch and deployment sequence
  • Journey around the Sun
  • Extreme exploration with Solar Orbiter and Parker Solar Probe
  • Anatomy of the Sun
  • Missions studying the Sun
  • Meet the Sun
  • Solar Orbiter team
  • Selected multimedia
  • Media services

To open the pdf file (16 MB) click on the image or on the link to publication below.

Published: 27 January 2020

Document reference: CDF-201(C)

In July 2018, ESA issued to the science community a Call for a Fast (F) mission opportunity in ESA's Science Programme. After a two-phase review process the Comet Interceptor mission was selected in June 2019 for going into the study phase, starting with a Concurrent Design Facility (CDF) mission assessment study.

The Comet Interceptor spacecraft will be launched in 2028 towards the Sun-Earth second Lagrange point, L2, on-board an Ariane 6.2 as co-passenger to the Ariel mission. The mission aims to intercept in a fly-by scenario a Long Period Comet (LPC), with Dynamically New Comets (DNCs) representing the highest priority type of LPC, or an interstellar body passing through our Solar System. The mission includes three elements, one main spacecraft (ESA) and two probes (one ESA and one JAXA) carried as payloads until the fly-by, at which point they are released to gather multi-point observations of the comet and its coma.

This second Comet Interceptor study carries on from the first Comet Interceptor study performed in the ESA CDF in early 2019. The second study was carried out by an interdisciplinary team of experts from ESA with the participation of JAXA and the mission proposer team in six sessions and two extra delta sessions, between October and December 2019.

Published: 11 December 2019

Download this interactive media kit to learn more about the launch of CHEOPS on 17 December 2019 and the science goals of the mission. CHEOPS, the CHaracterising ExOPlanet Satellite, is ESA's first mission dedicated to the study of exoplanets. It will observe bright stars that are already known to host planets, measuring minuscule brightness changes due to the planet's transit across the star's disc.

Update 20 Dec: A new version of the media kit was released containing the updated launch date, 18 December 2019, on p3 and p18. A typo was also corrected on p17.


  • Introduction
  • Event programme
  • Key messages
  • CHEOPS science themes
  • CHEOPS: an exoplanet follow-up mission
  • Exoplanet detection methods
  • Exoplanets discoveries
  • Examples of planetary systems
  • Characterising exoplanets with CHEOPS
  • CHEOPS observing programmes
  • What are exoplanets made of?
  • Open questions: How do planets form?
  • Open questions: How do planets evolve?
  • High photometric stability and precision
  • Where is CHEOPS?
  • Launch details and timeline
  • CHEOPS team and consortium
  • Selected images
  • Selected videos
  • Media services

To download the pdf file (25 MB) click on the image or on the link to publication below.

Published: 10 December 2019
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Solar Orbiter is a mission dedicated to solar and heliospheric physics. It will address big questions in Solar System science to help us understand how the Sun creates and controls the heliosphere, the giant bubble of plasma that surrounds the whole Solar System and influences Earth and the other planets within it. The spacecraft will provide close-up, high-latitude observations of the Sun to gain new information about the solar wind, the heliospheric magnetic field, solar energetic particles, transient interplanetary disturbances and the Sun's magnetic field.


  • Living with a star
  • Exploring our Sun
  • Anatomy of our Sun
  • Preparing for extreme environments
  • How Solar Orbiter will study the Sun
  • Launching and operating Solar Orbiter
  • Teamwork with Parker Solar Probe
  • An international enterprise
Published: 01 October 2019
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Document reference: ESA-SCI-F-ESTEC-RP-2019-001

The EPIG (ESA Probe for Investigation of the Giants) CDF study explored the feasibility of a European "stand-alone" mission to the Ice Giants (or Saturn as back-up). It corresponds to an ESA internal assessment of the capabilities to use only European technology to explore the outer planets.

The study was carried out by an interdisciplinary team of experts from ESA in eight sessions, starting with a kick-off on 28 March 2019 and ending with an Internal Final Presentation on 9 May 2019. This is a summary report of the EPIG CDF study. The full CDF study report will be made available at a later date.

Published: 16 July 2019

This brochure summarises the Herschel mission and its science achievements to date, capturing the basis for the science yet to come and its enduring legacy.

The European Space Agency's Herschel Space Observatory flew the largest single mirror ever built for a space telescope. At 3.5-metres in diameter the mirror collected long-wavelength radiation from some of the coldest and most distant objects in the Universe. In addition, Herschel was the only space observatory to cover a spectral range from the far infrared to sub-millimetre.

The Herschel mission leaves behind a lasting legacy in the form of a treasure trove of data, thousands of scientific papers, and a new generation of astronomers whose professional lives have been formed by working on this remarkable endeavour.


  • Foreword
  • The other half of the light
  • Tools of the trade
  • The Herschel mission
  • Gathering the light
  • The infrared Universe
  • Origins
  • Engines of star formation
  • From dust to planets
  • The water trail
  • An international enterprise
  • A lasting legacy

Published: 09 May 2019

CHEOPS is ESA's CHaracterising ExOPlanet Satellite. It is the first mission dedicated to studying bright, nearby stars that are already known to host exoplanets, in order to make high-precision observations of the planet's size as it passes in front of its host star. It will focus on planets in the super-Earth to Neptune size range, with its data enabling the bulk density of the planets to be derived – a first-step characterisation towards understanding these alien worlds.


  • Why exoplanets
  • Enter CHEOPS
  • How CHEOPS will characterise exoplanets
  • Designing a planet watcher
  • A European collaboration
  • Welcome onboard!

Published: 27 March 2019
Evidence has mounted in recent decades that outflows of matter and energy from the central few parsecs of our Galaxy have shaped the observed structure of the Milky Way on a variety of larger scales. On scales of 15 parsecs, the Galactic Centre has bipolar lobes that can be seen in both the X-ray and radio parts of the spectrum, indicating broadly collimated outflows from the centre, directed perpendicular to the Galactic plane. On larger scales, approaching the size of the Galaxy itself, γ-ray observations have revealed the so-called 'Fermi bubble' features, implying that our Galactic Centre has had a period of active energy release leading to the production of relativistic particles that now populate huge cavities on both sides of the Galactic plane. The X-ray maps from the ROSAT all-sky survey show that the edges of these cavities close to the Galactic plane are bright in X-rays. At intermediate scales (about 150 parsecs), radio astronomers have observed the Galactic Centre lobe, an apparent bubble of emission seen only at positive Galactic latitudes, but again indicative of energy injection from near the Galactic Centre. Here we report prominent X-ray structures on these intermediate scales (hundreds of parsecs) above and below the plane, which appear to connect the Galactic Centre region to the Fermi bubbles. We propose that these structures, which we term the Galactic Centre 'chimneys', constitute exhaust channels through which energy and mass, injected by a quasi-continuous train of episodic events at the Galactic Centre, are transported from the central few parsecs to the base of the Fermi bubbles.
Published: 21 March 2019
Collisionless shocks are ubiquitous throughout the universe: around stars, supernova remnants, active galactic nuclei, binary systems, comets, and planets. Key information is carried by electromagnetic emissions from particles accelerated by high Mach number collisionless shocks. These shocks are intrinsically nonstationary, and the characteristic physical scales responsible for particle acceleration remain unknown. Quantifying these scales is crucial, as it affects the fundamental process of redistributing upstream plasma kinetic energy into other degrees of freedom—particularly electron thermalization. Direct in situ measurements of nonstationary shock dynamics have not been reported. Thus, the model that best describes this process has remained unknown. Here, we present direct evidence demonstrating that the transition to nonstationarity is associated with electron-scale field structures inside the shock ramp.
Published: 27 February 2019
Bilobate comets—small icy bodies with two distinct lobes—are a common configuration among comets, but the factors shaping these bodies are largely unknown. Cometary nuclei, the solid centres of comets, erode by ice sublimation when they are sufficiently close to the Sun, but the importance of a comet's internal structure on its erosion is unclear. Here we present three-dimensional analyses of images from the Rosetta mission to illuminate the process that shaped the Jupiter-family bilobate comet 67P/Churyumov–Gerasimenko over billions of years. We show that the comet's surface and interior exhibit shear-fracture and fault networks, on spatial scales of tens to hundreds of metres. Fractures propagate up to 500 m below the surface through a mechanically homogeneous material. Through fracture network analysis and stress modelling, we show that shear deformation generates fracture networks that control mechani-cal surface erosion, particularly in the strongly marked neck trough of 67P/Churyumov–Gerasimenko, exposing its interior. We conclude that shear deformation shapes and structures the surface and interior of bilobate comets, particularly in the outer Solar System where water ice sublimation is negligible.
Published: 18 February 2019
The 3D velocities of M31 and M33 are important for understanding the evolution and cosmological context of the Local Group. Their most massive stars are detected by Gaia, and we use Data Release 2 (DR2) to determine the galaxy proper motions (PMs). We select galaxy members based on, e.g., parallax, PM, color–magnitude diagram location, and local stellar density. The PM rotation of both galaxies is confidently detected, consistent with the known line-of-sight rotation curves: Vrot = -206 ± 86 km s-1 (counterclockwise) for M31, and Vrot = 80 ± 52 km s-1 (clockwise) for M33. We measure the center-of-mass PM of each galaxy relative to surrounding background quasars in DR2. This yields that (μα*δ) equals (65 ± 18, -57 ± 15) μas yr-1 for M31 and (31 ± 19, -29 ± 16) μas yr-1 for M33. In addition to the listed random errors, each component has an additional residual systematic error of 16 μas yr-1. These results are consistent at 0.8σ and 1.0σ with the (2 and 3 times higher accuracy) measurements already available from Hubble Space Telescope (HST) optical imaging and Very Long Baseline Array water maser observations, respectively. This lends confidence that all these measurements are robust. The new results imply that the M31 orbit toward the Milky Way (MW) is somewhat less radial than previously inferred, Vtan,DR2+HST = 57+35-31 km s-1, and strengthen arguments that M33 may be on its first infall into M31. The results highlight the future potential of Gaia for PM studies beyond the MW satellite system.
Published: 07 February 2019
We present the first extensive radio to γ-ray observations of a fast-rising blue optical transient, AT 2018cow, over its first ~100 days. AT 2018cow rose over a few days to a peak luminosity Lpk ~ 4 × 1044 erg s-1, exceeding that of superluminous supernovae (SNe), before declining as L ∝ t-2. Initial spectra at δt ≲ 15 days were mostly featureless and indicated large expansion velocities v ~ 0.1c and temperatures reaching T ~ 3 × 104 K. Later spectra revealed a persistent optically thick photosphere and the emergence of H and He emission features with v ~ 4000 km s-1 with no evidence for ejecta cooling. Our broadband monitoring revealed a hard X-ray spectral component at E ≥ 10 keV, in addition to luminous and highly variable soft X-rays, with properties unprecedented among astronomical transients. An abrupt change in the X-ray decay rate and variability appears to accompany the change in optical spectral properties. AT 2018cow showed bright radio emission consistent with the interaction of a blast wave with vsh ~ 0.1c with a dense environment (Ṁ ~ 10-3–10-4 Myr-1 for vw = 1000 km s-1). While these properties exclude 56Ni-powered transients, our multiwavelength analysis instead indicates that AT 2018cow harbored a "central engine," either a compact object (magnetar or black hole) or an embedded internal shock produced by interaction with a compact, dense circumstellar medium. The engine released ~1050–1051.5 erg over ~103–105 s and resides within low-mass fast-moving material with equatorial–polar density asymmetry (Mej,fast ≲ 0.3 M). Successful SNe from low-mass H-rich stars (like electron-capture SNe) or failed explosions from blue supergiants satisfy these constraints. [Remainder of abstract truncated due to character limitation]
Published: 06 February 2019
The concordance model (Λ cold dark matter (ΛCDM) model, where Λ is the cosmological constant) reproduces the main current cosmological observations1,2,3,4 assuming the validity of general relativity at all scales and epochs and the presence of CDM and of Λ, equivalent to dark energy with a constant density in space and time. However, the ΛCDM model is poorly tested in the redshift interval between the farthest observed type Ia supernovae5 and the cosmic microwave background. We present measurements of the expansion rate of the Universe based on a Hubble diagram of quasars. Quasars are the most luminous persistent sources in the Universe, observed up to redshifts of z ≈ 7.5 (refs. 6,7). We estimate their distances following a method developed by our group8,9,10, based on the X-ray and ultraviolet emission of the quasars. The distance modulus/redshift relation of quasars at z < 1.4 is in agreement with that of supernovae and with the concordance model. However, a deviation from the ΛCDM model emerges at higher redshift, with a statistical significance of ~4σ. If an evolution of the dark energy equation of state is allowed, the data suggest dark energy density increasing with time.
Published: 28 January 2019
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License.

The scale of groundwater upwelling on Mars, as well as its relation to sedimentary systems, remains an ongoing debate. Several deep craters (basins) in the northern equatorial regions show compelling signs that large amounts of water once existed on Mars at a planet-wide scale. The presence of water-formed features, including fluvial Gilbert and sapping deltas fed by sapping valleys, constitute strong evidence of groundwater upwelling resulting in long term standing bodies of water inside the basins. Terrestrial field evidence shows that sapping valleys can occur in basalt bedrock and not only in unconsolidated sediments. A hypothesis that considers the elevation differences between the observed morphologies and the assumed basal groundwater level is presented and described as the "dike-confined water" model, already present on Earth and introduced for the first time in the Martian geological literature. Only the deepest basins considered in this study, those with bases deeper than −4000 m in elevation below the Mars datum, intercepted the water-saturated zone and exhibit evidence of groundwater fluctuations. The discovery of these groundwater discharge sites on a planet-wide scale strongly suggests a link between the putative Martian ocean and various configurations of sedimentary deposits that were formed as a result of groundwater fluctuations during the Hesperian period. This newly recognized evidence of water-formed features significantly increases the chance that biosignatures could be buried in the sediment. These deep basins (groundwater-fed lakes) will be of interest to future exploration missions as they might provide evidence of geological conditions suitable for life.

Published: 21 January 2019
20-Jul-2024 04:31 UT

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