NewAthena (Advanced Telescope for High Energy Astrophysics)

Quick facts

Overview

Summary

Description

The Advanced Telescope for High Energy Astrophysics (NewAthena) mission is a planned X-ray satellite observatory of the European Space Agency (ESA), open to the whole astronomical community worldwide, aiming at breakthrough discoveries in every field of modern astrophysics. In particular, NewAthena will investigate the origins and formation of hot gas large-scale structures, as well as the influence of supermassive black holes in active galactic nuclei on the cosmological evolution of galaxies.

Mission Capabilities

NewAthena carries two instruments, the Wide Field Imager (WFI), an array of silicone active pixel sensors with an integrated detector/amplifier structure, and the X-ray Integral Field Unit (X-IFU), an X-ray spectrometer consisting of a microcalorimeter array. WFI provides simultaneous spectral and time-resolved photon counting, and will play a key role in the NewAthena’s mission objective to complete a census of black hole growth. X-IFU is a pixelated transition edge sensor (TES) achieving an unprecedented energy resolving power. It will investigate the chemical and dynamical state of the dominant component of baryonic matter in the Universe.

Performance Specifications

WFI has a field of view (FoV) of 40’ x 40’, with a spectral resolution of 170 eV at 6 keV. X-IFU has a spectral resolution of 4 eV, up to 7 keV, over a 4’ equivalent diameter field-of-view (over the hexagonal shape), covered with ~1500 pixels of 5” size. Both instruments operate in an energy range between about 0.2 keV and 12.0 keV. The instruments will be placed in the focal plane of an X-ray telescope enabling an angular resolution of 9” on-axis (Half-Energy Width).

NewAthena will operate from the First Lagrange point, L1, a gravitationally semi-stable point 1.5 million km from Earth.

Overview

The Advanced Telescope for High Energy Astrophysics (NewAthena) mission is a planned general purpose open X-ray satellite observatory designed and developed by the European Space Agency (ESA). NewAthena represents a significant improvement over existing X-ray observatories, such as ESA’s XMM-Newton mission and NASA’s Chandra mission. 3) 4) 5) 7) 9) 10) 13) 14)

NewAthena is designed to be a general-purpose open observatory, able to address a wide range of current astrophysical topics.  Observations include: distant gamma-ray bursts, the hot gas found in the space around clusters of galaxies, accreting compact objects such as black holes and neutron stars, supernovae and their remnants, white dwarfs, exoplanets and their parent stars, Jupiter's auroras and comets in our Solar System, and the interstellar medium (gas and dust). NewAthena will address key questions in astrophysics, among them:

• Ascertain the nature of the primary source of high-energy radiation in stellar-mass and supermassive accreting black holes,
• Determine the mechanism(s) regulating the cosmological co-evolution of accreting black holes and their host galaxies,
• Measure the space density of the active galactic nuclei (AGN) that dominate black hole growth,
• Constrain the kinematics of hot gas and metals in massive halos (galaxy clusters and groups),
• Map the properties of the most common baryonic reservoirs in the Universe, and probe their evolution and connection to the cosmic web,
• Constrain supernova explosion mechanisms through the determination of the 3-dimensional kinematics, ionisation state and abundances in young remnants,
• Provide novel and unprecedented constraints on the Equation of State of Neutron Stars,
• Study Solar-Planet Interactions through the stellar magnetic activity in exoplanet-hosting systems.

 Athena will also provide a key contribution to multi-messenger astrophysics, in synergy with gravitational wave arrays and neutrino telescopes.

These goals will be achieved by a significantly increased collecting area, energy resolution, and survey capabilities. These are made possible through the use of novel Silicon Pore Optics (SPO) mirror technology, and two instruments in the focal plane: the Wide Field Imager (WFI), and the X-ray Integral Field Unit (X-IFU). The NewAthena mission has been selected for the second Large-class mission slot in ESA’s Cosmic Vision 2015-25 plan.

Launch

NewAthena will operate from the First Lagrange Point, L1, a gravitationally semi-stable point approximately 1,500,000 km from Earth. It will operate from this point for at least five years, with an overall design lifetime of 10 years. 5) 13)

Mission Status

• May 1, 2024: Industrial and scientific activities have formally restarted at ESA, aiming at a mission “adoption” in the first quarter of 2027, followed by a 9-year implementation phase.
• November 8, 2023: Following a year-long ‘design to cost’ budgeting process, ESA’s Science Program Committee endorsed a rescoped version of the mission, now known as ‘NewAthena’. The resulting program features a simplified mission design to meet cost requirements. 19)
• June 27, 2014: ESA has selected the ATHENA advanced X-ray telescope as the second L-class mission for its Cosmic Vision program 19)

Sensor Complement

Silicone Pore Optics

NewAthena will employ a novel silicon pore optics (SPO) mirror system to reflect incoming X-rays into the satellite instruments. SPO systems are lightweight, high resolution X-ray optics, that use monocrystalline, double-sided, super-polished silicon wafers as mirrors. SPOs are able to combine the requirement for a large collecting area with high angular resolution, while being a lightweight and cost efficient solution. Pre-existing technologies, such as polished glass, nickel, electroforming and foil optics would lead to excessive costs and weight, and are unable to achieve the desired combination of high angular resolution and collection area. 1) 9) 10) 15) 16) 18) 20)

In creating SPOs, ultra-flat silicon wafers are used. These wafers are subjected to a process of anisotropic etching, creating a grooved surface which forms the basic pore structure. Etched wafers are then precisely aligned, stacked and bonded together through heating, forming a monolithic, lightweight structure. These bonded wafer stacks are shaped into a curved form, designed according to the specific focal requirements of the telescope. The NewAthena SPO telescope will have a 12 m focal length and a 9 arcsecond half energy width (HEW) on-axis angular resolution.

Wide Field Imager

The NewAthena Wide Field Imager (WFI) consists of two specialised sub-instruments, a large area detector, covering an area of 40 arcminutes, and a small area detector capable of processing high count rates. Both components are variations of the same sensor principle, an array of silicone active pixel sensors using an integrated detector/amplifier structure. WFI specifically uses a Depleted P-channel Field Effect Transistor (DePFET), which has an extremely low detector capacitance, providing excellent signal to noise ratios and energy resolution.

DePFET structures consist of a p-channel field effect transistor, integrated on the surface of a high resistivity n-type silicone bulk, as shown below. DePFET detectors function on the principle of sideward depletion, essentially the depletion of a large volume of high-resistivity silicon material through a small anode receiving a minimum signal capacitance. Through this principle, the bulk can be completely depleted, and a potential minimum for electrons can be generated. The presence of any charge within this minimum influences additional charge carriers in the transistor channel and therefore changes its electrical conductivity. As incoming ionising radiation generates electron-hole-pairs within the depleted silicon bulk, the charge carriers are separated by the electric field, while the electrons are collected in the closest potential minimum. The resulting change in channel conductivity can be used to sense charge in the corresponding potential minimum, once it has been converted to a voltage or current signal. In this way, the DePFET structure functions as a detector for ionising radiation. DePFET active pixel sensors, in comparison to traditional charge coupled device (CCD) detectors, provide in-situ charge amplification, with an integrated amplifier in every pixel, allowing a fast, low noise and random access readout. As well as this, the application of the DePFET structure incorporates the benefits of a sideward depleted device to the instrument, allowing full bulk depletion and a large sensitive volume.

WFI images in the 0.2 keV - 12 keV energy range as well as simultaneously providing spectrally and time-resolved photon counting. The instrument has a field of view (FoV) of 40’ x 40’. The large DePFET detector has a grid of 1024 x 1024 pixels, divided into four quadrants, while the fast DePFET detector features a 64 x 64-pixel grid. Both detectors have a pixel size of 130 µm x 130 µm corresponding to a linear dimension of 2.2” on the sky vault for the assumed 12 m focal length of the telescope. WFI uses a rolling shutter operating mode, with a full frame time resolution of 80 µs for the fast detector and <5 ms for the large detector. The fast DePFET detector has a count rate capability where it achieves > 80% throughout and <1% pile up when defocused and observing an X-ray source of intensity 1 Crab. 2) 3) 6) 7) 12)

X-Ray Integral Field Unit

The NewAthena X-Ray Integral Field Unit (X-IFU) is an X-ray spectrometer that will probe the dynamical and chemical state of baryonic matter, investigate the role of black holes in shaping the Universe and their surroundings, and provide hot plasma diagnostics in a variety of astrophysical settings. The primary detector of X-IFU is an array of 1500 X-ray absorbers, positioned above highly sensitive microcalorimeters, known as transition edge sensors (TES). These sensors are able to detect the heat generated by X-ray photons when they are absorbed and thermalised, and use a thin film of superconducting material, molybdenum and gold (Mo/Au) in the case of X-IFU, maintained near its transition temperature, to detect miniscule changes in temperature. This is possible as, when near transition temperature, slight changes in temperature result in extreme and measurable changes in resistance, as shown below. The X-IFU Mo/Au film uses the proximity effect, where the two metals act as a single film with a transition temperature between 800 mK and 0 k. These cryogenic temperatures are required for high energy resolution, as the energy resolution scale switches temperature. In addition to its primary detector, X-IFU contains a cryogenic anti-coincidence detector, which surrounds the primary detector. This instrument segment is employed to improve measurement accuracy by reducing background noise. As background particles that strike the primary detector will generate a similar signal to observed X-rays, differentiation between intended observations and background noise poses a significant problem. However, due to the inclusion of an anti-coincidence detector, background radiation will also be detected by the transition edge sensors housed by this instrument segment, while X-rays observed by X-IFU will not, meaning that simultaneous events in the primary and anti-coincidence detectors can be rejected as background radiation, improving instrument accuracy.

X-IFU has been constructed by a French-led consortium, including the National Centre for Space Studies (CNES) and the Institute for Research in Astrology and Physics (IRAP), with Italy and the Netherlands as key contributors and science and hardware contributions from eight other ESA member states- Belgium, Czech Republic, Finland, Germany, Ireland, Poland, Spain, and Switzerland. The instrument has a spectral resolution of 4 eV, up to 7 keV, with an energy range of 0.2 keV - 12.0 keV. As the instrument requires cryogenic temperatures to reach such a resolution, it employs a passive cooling system, centred around three L-shaped cryogenic radiators known as V-grooves which keep the instrument in a 50 K environment. As well as this, the detector stage is maintained by a cooling system which includes a Dewar vessel with an outer envelope at 50 K, which hosts the cold core that houses the instrument itself. The cooling system also consists of a remote cryocooler, known as 4K Cooler, which provides active cooling in the 20K to 4K region, as well as a multistage Adiabatic Demagnetization Refrigerator (ADR), which is able to further cool the instrument down to 50 mK from temperatures near 4K. This cooling chain is shown below. 4) 8) 11) 17) 22)

References  

1) Advanced Telescope for High Energy Astrophysics, URL: https://www.the-athena-X-ray-observatory.eu/en

2) The Athena Wide Field Imager, URL: https://www.mpe.mpg.de/ATHENA-WFI/

3) “NewAthena” ESA Cosmos, URL: https://www.cosmos.esa.int/web/athena

4) “Athena | Kavli Institute for Particle Astrophysics and Cosmology (KIPAC).” Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), URL: https://kipac.stanford.edu/research/projects/athena

5) “Athena to study the hot and energetic Universe.” European Space Agency, 27 June 2014, URL: https://www.esa.int/Science_Exploration/Space_Science/Athena_to_study_the_hot_and_energetic_Universe

6) “ATHENA Wide Field Imager.” Halbleiterlabor der Max-Planck-Gesellschaft, URL: https://www.hll.mpg.de/2968109/ATHENA

7) “The Athena X-ray Observatory.” Max Planck Institute for Extraterrestrial Physics, URL: https://www.mpe.mpg.de/Athena

8) Barret, Didier, et al. “The Athena X-ray Integral Field Unit (X-IFU).” URL: https://www.the-athena-X-ray-observatory.eu/en/node/261

9) Barriere, Nicolas M., and Marcos Bavdaz. “Silicon Pore Optics.” URL: https://arxiv.org/abs/2206.11291.

10) Bavdaz, Marcos. “Mirror Status Report.” 25 September 2018, URL: https://www.isdc.unige.ch/athena/Repository/Open_access/Second_Athena_Conference/Bavdaz.pdf.

11) “Building the instrument.” Athena X-IFU, URL: https://x-ifu.irap.omp.eu/x-ifu/building-the-instrument

12) “DEPFET detectors.” Halbleiterlabor der Max-Planck-Gesellschaft, URL: https://www.hll.mpg.de/3049931/DEPFET

13) “ESA Science & Technology - Athena to study the hot and energetic Universe.” ESA Science & Technology, 27 June 2014, URL: https://sci.esa.int/web/cosmic-vision/-/54241-athena-to-study-the-hot-and-energetic-universe

14) “Final three for ESA's next medium science mission.” European Space Agency, 8 November 2023, URL: https://www.esa.int/Science_Exploration/Space_Science/Final_three_for_ESA_s_next_medium_science_mission

15) “High-energy optics.” cosine, URL: https://www.cosine.nl/technology/high-energy-optics/

16) Kraft, Stefan. “Silicon Pore Optics: novel lightweight high-resolution X-ray optics developed for XEUS.” ESA Science & Technology, URL: https://sci.esa.int/documents/34490/36224/1567255375439-Silicon_Pore_Optics__novel_lightweight_highresolution_Xray_optics_developed_for_XEUS.pdf

17) “MIT Experimental Cosmology and Astrophysics Laboratory.” MIT, URL: https://web.mit.edu/figueroagroup/ucal/ucal_tes/index.html

18) “Silicon Pore Optics mirror modules for ATHENA telescope.” cosine, URL: https://www.cosine.nl/cases/silicon-pore-optics-mirror-modules-spo-for-astronomy/

19) “Status and milestones | Athena X-ray observatory.” Athena X-ray observatory, URL: https://www.the-athena-X-ray-observatory.eu/en/mission/status-and-milestones

20) Turner, Martin JL, and Günther Hasinger. “IXO Flight Mirror Assembly.” Astrophysics Science Division, URL:  https://asd.gsfc.nasa.gov/archive/ixo/technology/fmaSiliconPore.html

21) “X-IFU in a nutshell.” Athena X-IFU, URL: https://x-ifu.irap.omp.eu/x-ifu/x-ifu-in-anutshell