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    • By European Space Agency
      Global warming is driving the rapid melting of the Greenland Ice Sheet, contributing to global sea level rise and disrupting weather patterns worldwide. Because of this, precise measurements of its changing shape are of critical importance for adapting to climate change.
      Now, scientists have delivered the first measurements of the Greenland Ice Sheet’s changing shape using data from ESA's CryoSat and NASA's ICESat-2 ice missions.
      View the full article
    • By European Space Agency
      Video: 00:10:27 In 1975, 10 European countries came together with a vision to collaborate on key space activities: science and astronomy, launch capabilities and space applications: the European Space Agency, ESA, was born.
      In 2025, we mark half a century of joint European achievement – filled with firsts and breakthroughs in science, exploration and technology, and the space infrastructure and economy that power Europe today.
       
      During the past five decades ESA has grown, developing ever bolder and bigger projects and adding more Member States, with Slovenia joining as the latest full Member State in January.
       
      We’ll also celebrate the 50th anniversary of ESA’s Estrack network, 30 years of satellite navigation in Europe and 20 years since ESA launched the first demonstration satellite Giove-A which laid the foundation for the EU’s own satnav constellation Galileo. Other notable celebrations are the 20th anniversary of ESA’s Business Incubation Centres, or BICs, and the 30th year in space for SOHO, the joint ESA and NASA Solar and Heliospheric Observatory.
       
      Sadly though, 2025 will mean end of science operations for Integral and Gaia. Integral, ESA's gamma-ray observatory has exotic objects in space since 2002 and Gaia concludes a decade of mapping the stars. But as some space telescopes retire, another one provides its first full data release. Launched in 2023, we expect Euclid’s data release early in the new year.
       
      Launch-wise, we’re looking forward to Copernicus Sentinel-4 and -5 (Sentinel-4 will fly on an MTG-sounder satellite and Sentinel-5 on the MetOp-SG-A1 satellite), Copernicus Sentinel-1D, Sentinel-6B and Biomass. We’ll also launch the SMILE mission, or Solar wind Magnetosphere Ionosphere Link Explorer, a joint mission with the Chinese academy of science.
       
      The most powerful version of Europe’s new heavy-lift rocket, Ariane 6, is set to fly operationally for the first time in 2025. With several European commercial launcher companies planning to conduct their first orbital launches in 2025 too, ESA is kicking off the European Launcher Challenge to support the further development of European space transportation industry.
       
      In human spaceflight, Polish ESA project astronaut Sławosz Uznański will fly to the ISS on the commercial Axiom-4 mission. Artemis II will be launched with the second European Service Module, on the first crewed mission around the Moon since 1972.
      The year that ESA looks back on a half century of European achievement will also be one of key decisions on our future. At the Ministerial Council towards the end of 2025, our Member States will convene to ensure that Europe's crucial needs, ambitions and the dreams that unite us in space become reality.
      So, in 2025, we’ll celebrate the legacy of those who came before but also help establish a foundation for the next 50 years. Join us as we look forward to a year that honours ESA’s legacy and promises new milestones in space.
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    • By European Space Agency
      Video: 00:00:00 Watch the replay of the media information session in which ESA Director General Josef Aschbacher and ESA Council Chair Renato Krpoun (CH) update journalists on the key decisions taken at the ESA Council meeting, held at ESA Headquarters in Paris on 17 and 18 December 2024.
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    • By European Space Agency
      Video: 00:11:10 In 2024, ESA continued to drive Europe’s innovation and excellence in space, equipping the continent with advanced tools and knowledge to address global and local challenges. The year saw pioneering missions, cutting-edge satellites and the pivotal restoration of Europe’s independent access to space. 
      The first Ariane 6 launch was perhaps ‘the’ highlight of the year but it was only one of many achievements. We saw the last Vega launch and then the return to flight of Vega-C, the more powerful, upgraded version carrying Sentinel-1C.
      Far away in our Solar System, the ESA/JAXA BepiColombo spacecraft performed twoMercury flybys in 2024, needed so that it can enter orbit around Mercury in 2026. Juice also performed a crucial gravity assist, this time becoming the first spacecraft to conduct a Moon-Earth double flyby on its way to Jupiter. 
      Twenty years after ESA’s Rosetta was launched and 10 years since its historic arrival at the comet 67P/Churyumov-Gerasimenko, we launched another spacecraft to a small body, the Hera planetary defence mission to investigate asteroid Dimorphos.
      2024 was an important year for Europe’s Galileo constellation which continued to expand with the launch of four new satellites and an updated Galileo ground system. The year also saw the launch of ESA’s Proba-3 mission: two precision formation-flying satellites forming a solar coronagraph to study the Sun’s faint corona. 
      In human spaceflight, Europe continues to contribute to science from the ISS as Andreas Mogensen’s Huginn mission continued into 2024. Andreas even met up in space with ESA project astronaut Marcus Wandt who was launched on his Muninn mission, making it the first time two Scandinavians were in space together. 
      Meanwhile the latest class of ESA astronauts completed basic training and graduated in April. Two of them, Sophie and Raphaël, were then assigned to long-duration missions to the ISS in 2026.
      We made crucial steps for Europe in gaining access to the Moon: the inauguration of our LUNA facility with DLR, and the delivery of a third European Service Module for NASA’s Orion spacecraft as part of the Artemis programme.
      Europe is also contributing to the international Lunar Gateway and developing and ESA lunar lander called Argonaut. These landers will rely on ESA Moonlight, the programme to establish Europe’s first dedicated satellite constellation for lunar communication and navigation.
      As 2024 draws to a close, ESA’s achievements this year have reinforced Europe’s role in space. ESA’s journey continues to explore new frontiers, shaping the space landscape for generations to come.
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    • By NASA
      X-rays are radiated by matter hotter than one million Kelvin, and high-resolution X-ray spectroscopy can tell us about the composition of the matter and how fast and in what direction it is moving. Quantum calorimeters are opening this new window on the Universe. First promised four decades ago, the quantum-calorimeter era of X-ray astronomy has finally dawned.
      Photo of the XRISM/Resolve quantum-calorimeter array in its storage container prior to integration into the instrument. The 6×6 array, 5 mm on a side, consists of independent detectors – each one a thermally isolated silicon thermistor with a HgTe absorber. The spectrometer consisting of this detector and other essential technologies separates astrophysical X-ray spectra into about 2400 resolution elements, which can be thought of as X-ray colors.NASA GSFC A quantum calorimeter is a device that makes precise measurements of energy quanta by measuring the temperature change that occurs when a quantum of energy is deposited in an absorber with low heat capacity. The absorber is attached to a thermometer that is somewhat decoupled from a heat sink so that the sensor can heat up and then cool back down again. To reduce thermodynamic noise and the heat capacity of the sensor, operation at temperatures less than 0.1 K is required. 
      The idea for thermal measurement of small amounts of energy occurred in several places in the world independently when scientists observed pulses in the readout of low-temperature thermometers and infrared detectors. They attributed these spurious signals to passing cosmic-ray particles, and considered optimizing detectors for sensitive measurement of the energy of particles and photons.
      The idea to develop such sensors for X-ray astronomy was conceived at Goddard Space Flight Center in 1982 when X-ray astronomers were considering instruments to propose for NASA’s planned Advanced X-ray Astrophysics Facility (AXAF). In a fateful conversation, infrared astronomer Harvey Moseley suggested thermal detection could offer substantial improvement over existing solid-state detectors. Using Goddard internal research and development funding, development advanced sufficiently to justify, just two years later, proposing a quantum-calorimeter X-ray Spectrometer (XRS) for inclusion on AXAF. Despite its technical immaturity at the time, the revolutionary potential of the XRS was acknowledged, and the proposal was accepted.
      The AXAF design evolved over the subsequent years, however, and the XRS was eliminated from its complement of instruments. After discussions between NASA and the Japanese Institute of Space and Astronautical Science (ISAS), a new XRS was included in the instrument suite of the Japanese Astro-E X-ray observatory. Astro-E launched in 2000 but did not reach orbit due to an anomaly in the first stage of the rocket. Astro-E2, a rebuild of Astro-E, was successfully placed in orbit in 2005 and renamed Suzaku, but the XRS instrument ceased operation before observations started due to loss of the liquid helium, an essential part of the detector cooling system, caused by a faulty storage system.
      A redesigned mission, Astro-H, that included a quantum-calorimeter instrument with a redundant cooling system was successfully launched in 2016 and renamed Hitomi. Hitomi’s Soft X-ray Spectrometer (SXS) obtained high resolution spectra of the Perseus cluster of galaxies and a few other sources before a problem with the attitude control system caused the mission to be lost roughly one month after launch. Even so, Hitomi was the first orbiting observatory to obtain a scientific result using X-ray quantum calorimeters. The spectacular Perseus spectrum generated by the SXS motivated yet another attempt to implement a spaceborne quantum-calorimeter spectrometer.
      The X-ray Imaging and Spectroscopy Mission (XRISM) was launched in September 2023, with the spectrometer aboard renamed Resolve to represent not only its function but also the resolve of the U.S./Japan collaboration to study the Universe through the window of this new capability. XRISM has been operating well in orbit for over a year.  
      Development of the Sensor Technology
      Development of the sensor technology employed in Resolve began four decades ago. Note that an X-ray quantum-calorimeter spectrometer requires more than the sensor technology. Other technologies, such as the coolers that provide a
      The sensors used from XRS through Resolve were all based on silicon-thermistor thermometers and mercury telluride (HgTe) X-ray absorbers. They used arrays consisting of 32 to 36 pixels, each of which was an independent quantum calorimeter.  Between Astro-E and Astro-E2, a new method of making the thermistor was developed that significantly reduced its low-frequency noise. Other fabrication advances made it possible to make reproducible connections between absorbers and thermistors and to fit each thermistor and its thermal isolation under its X-ray absorber, making square arrays feasible.
      Through a Small Business Innovation Research (SBIR) contract executed after the Astro-E2 mission, EPIR Technologies Inc. reduced the specific heat of the HgTe absorbers. Additional improvements made to the cooler of the detector heat sink allowed operation at a lower temperature, which further reduced the specific heat. Together, these changes enabled the pixel width to be increased from 0.64 mm to 0.83 mm while still achieving a lower heat capacity, and thus improving the energy resolution. From Astro-E through Astro-H, the energy resolution for X-rays of energy around 6000 eV improved from 11 eV, to 5.5 eV, to 4 eV. No changes to the array design were made between Astro-H and XRISM.
      Resolve detector scientist Caroline Kilbourne installing the flight Resolve quantum-calorimeter array into the assembly that provides its electrical, thermal, and mechanical interfaces.NASA GSFC Over the same period, other approaches to quantum-calorimeter arrays optimized for the needs of future missions were developed. The use of superconducting transition-edge sensors (TES) instead of silicon (Si) thermistors led to improved energy resolution, more pixels per array, and multiplexing (a technique that allows multiple signals to be carried on a single wire). Quantum-calorimeter arrays with thousands of pixels are now standard, such as in the NASA contribution to the future European New Advanced Telescope for High-ENergy Astrophysics (newAthena) mission. And quantum calorimeters using paramagnetic thermometers — which unlike TES and Si thermistors require no dissipation of heat in the thermometer for it to be read out — combined with high-density wiring are a promising route for realizing even larger arrays. (See Astrophysics Technology Highlight on these latest developments.)
      The Resolve instrument aboard XRISM (X-ray Imaging and Spectroscopy Mission) captured data from the center of galaxy NGC 4151, where a supermassive black hole is slowly consuming material from the surrounding accretion disk. The resulting spectrum reveals the presence of iron in the peak around 6.5 keV and the dips around 7 keV, light thousands of times more energetic that what our eyes can see. Background: An image of NGC 4151 constructed from a combination of X-ray, optical, and radio light.Spectrum: JAXA/NASA/XRISM Resolve. Background: X-rays, NASA/CXC/CfA/J.Wang et al.; optical, Isaac Newton Group of Telescopes, La Palma/Jacobus Kapteyn Telescope; radio, NSF/NRAO/VLA Results from Resolve
      So, what is Resolve revealing about the Universe? Through spectroscopy alone, Resolve allows us to construct images of complex environments where collections of gas and dust with various attributes exist, emitting and absorbing X-rays at energies characteristic of their various compositions, velocities, and temperatures. For example, in the middle of the galaxy known as NCG 4151 (see figure above), matter spiraling into the central massive black hole forms a circular structure that is flat near the black hole, more donut-shaped further out, and, according to the Resolve data, a bit lumpy. Matter near the black hole is heated up to X-ray-emitting temperatures and irradiates the matter in the circular structure. The Resolve spectrum has a bright narrow emission line (peak) from neutral iron atoms that must be coming from colder matter in the circular structure, because hotter material would be ionized, and would have a different emission signature. Nonetheless, the shape of the iron line needs three components to describe it, each coming from a different lump in the circular structure. The presence of absorption lines (dips) in the spectrum provides further detail about the structure of the infalling matter.
      A second example is the detection of X-ray emission by Resolve from the debris of stars that have exploded, such as N132D (see figure below), that will improve our understanding of the explosion mechanism and how the elements produced in stars get distributed, and allow us to infer the type of star each was before ending in a supernova. Elements are identified by their characteristic emission lines, and shifts of those lines via the Doppler effect tell us how fast the material is moving.
      XRISM’s Resolve instrument captured data from supernova remnant N132D in the Large Magellanic Cloud to create the most detailed X-ray spectrum of the object ever made. The spectrum reveals peaks associated with silicon, sulfur, argon, calcium, and iron. Inset at right is an image of N132D captured by XRISM’s Xtend instrument.JAXA/NASA/XRISM Resolve and Xtend These results are just the beginning. The rich Resolve data sets are identifying complex velocity structures, rare elements, and multiple temperature components in a diverse ensemble of cosmic objects. Welcome to the quantum calorimeter era! Stay tuned for more revelations!
      Project Leads: Dr. Caroline Kilbourne, NASA Goddard Space Flight Center (GSFC), for silicon-thermistor quantum calorimeter development from Astro-E2 through XRISM and early TES development. Foundational and other essential leadership provided by Dr. Harvey Moseley, Dr. John Mather, Dr. Richard Kelley, Dr. Andrew Szymkowiak, Mr. Brent Mott, Dr. F. Scott Porter, Ms. Christine Jhabvala, Dr. James Chervenak (GSFC at the time of the work) and Dr. Dan McCammon (U. Wisconsin).
      Sponsoring Organizations and Programs:  The NASA Headquarters Astrophysics Division sponsored the projects, missions, and other efforts that culminated in the development of the Resolve instrument.
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