The X-ray Integral Field Unit (X-IFU) is the high resolution X-ray spectrometer of the ESA Athena X-ray observatory. Over a field of view of 5’ equivalent diameter, it will deliver X-ray spectra from 0.2 to 12 keV with a spectral resolution of 2.5 eV up to 7 keV on ∼ 5” pixels. The X-IFU is based on a large format array of super-conducting molybdenum-gold Transition Edge Sensors cooled at ∼ 90 mK, each coupled with an absorber made of gold and bismuth with a pitch of 249 μm. A cryogenic anti-coincidence detector located underneath the prime TES array enables the non X-ray background to be reduced. A bath temperature of ∼ 50 mK is obtained by a series of mechanical coolers combining 15K Pulse Tubes, 4K and 2K Joule-Thomson coolers which pre-cool a sub Kelvin cooler made of a 3He sorption cooler coupled with an Adiabatic Demagnetization Refrigerator. Frequency domain multiplexing enables to read out 40 pixels in one single channel. A photon interacting with an absorber leads to a current pulse, amplified by the readout electronics and whose shape is reconstructed on board to recover its energy with high accuracy. The defocusing capability offered by the Athena movable mirror assembly enables the X-IFU to observe the brightest X-ray sources of the sky (up to Crab-like intensities) by spreading the telescope point spread function over hundreds of pixels. Thus the X-IFU delivers low pile-up, high throughput (< 50%), and typically 10 eV spectral resolution at 1 Crab intensities, i.e. a factor of 10 or more better than Silicon based X-ray detectors. In this paper, the current X-IFU baseline is presented, together with an assessment of its anticipated performance in terms of spectral resolution, background, and count rate capability. The X-IFU baseline configuration will be subject to a preliminary requirement review that is scheduled at the end of 2018.
The X-ray Integral Field Unit (X-IFU) on board the Advanced Telescope for High-ENergy Astrophysics (Athena) will provide spatially resolved high-resolution X-ray spectroscopy from 0.2 to 12 keV, with ~ 5" pixels over a field of view of 5 arc minute equivalent diameter and a spectral resolution of 2.5 eV up to 7 keV. In this paper, we first review the core scientific objectives of Athena, driving the main performance parameters of the X-IFU, namely the spectral resolution, the field of view, the effective area, the count rate capabilities, the instrumental background. We also illustrate the breakthrough potential of the X-IFU for some observatory science goals. Then we brie y describe the X-IFU design as defined at the time of the mission consolidation review concluded in May 2016, and report on its predicted performance. Finally, we discuss some options to improve the instrument performance while not increasing its complexity and resource demands (e.g. count rate capability, spectral resolution).
The Large Observatory For x-ray Timing (LOFT) is a mission concept which was proposed to ESA as M3 and M4 candidate in the framework of the Cosmic Vision 2015-2025 program. Thanks to the unprecedented combination of effective area and spectral resolution of its main instrument and the uniquely large field of view of its wide field monitor, LOFT will be able to study the behaviour of matter in extreme conditions such as the strong gravitational field in the innermost regions close to black holes and neutron stars and the supra-nuclear densities in the interiors of neutron stars. The science payload is based on a Large Area Detector (LAD, >8m<sup>2</sup> effective area, 2-30 keV, 240 eV spectral resolution, 1 degree collimated field of view) and a Wide Field Monitor (WFM, 2-50 keV, 4 steradian field of view, 1 arcmin source location accuracy, 300 eV spectral resolution). The WFM is equipped with an on-board system for bright events (e.g., GRB) localization. The trigger time and position of these events are broadcast to the ground within 30 s from discovery. In this paper we present the current technical and programmatic status of the mission.
The LOFT mission concept is one of four candidates selected by ESA for the M3 launch opportunity as Medium Size missions of the Cosmic Vision programme. The launch window is currently planned for between 2022 and 2024. LOFT is designed to exploit the diagnostics of rapid X-ray flux and spectral variability that directly probe the motion of matter down to distances very close to black holes and neutron stars, as well as the physical state of ultradense matter. These primary science goals will be addressed by a payload composed of a Large Area Detector (LAD) and a Wide Field Monitor (WFM). The LAD is a collimated (<1 degree field of view) experiment operating in the energy range 2-50 keV, with a 10 m<sup>2</sup> peak effective area and an energy resolution of 260 eV at 6 keV. The WFM will operate in the same energy range as the LAD, enabling simultaneous monitoring of a few-steradian wide field of view, with an angular resolution of <5 arcmin. The LAD and WFM experiments will allow us to investigate variability from submillisecond QPO’s to yearlong transient outbursts. In this paper we report the current status of the project.
The High Time Resolution Spectrometer (HTRS) is one of the five focal plane instruments of the International
X-ray Observatory (IXO). The HTRS is the only instrument matching the top level mission requirement of
handling a one Crab X-ray source with an efficiency greater than 10%. It will provide IXO with the capability
of observing the brightest X-ray sources of the sky, with sub-millisecond time resolution, low deadtime, low
pile-up (less than 2% at 1 Crab), and CCD type energy resolution (goal of 150 eV FWHM at 6 keV). The HTRS
is a non-imaging instrument, based on a monolithic array of Silicon Drift Detectors (SDDs) with 31 cells in a
circular envelope and a X-ray sensitive volume of 4.5 cm<sup>2</sup> x 450 μm. As part of the assessment study carried
out by ESA on IXO, the HTRS is currently undergoing a phase A study, led by CNES and CESR. In this
paper, we present the current mechanical, thermal and electrical design of the HTRS, and describe the expected
performance assessed through Monte Carlo simulations.
XEUS has been recently selected by ESA for an assessment study. XEUS is a large mission candidate for the
Cosmic Vision program, aiming for a launch date as early as 2018. XEUS is a follow-on to ESA's Cornerstone
X-Ray Spectroscopy Mission (XMM-Newton). It will be placed in a halo orbit at L2, by a single Ariane 5 ECA,
and comprises two spacecrafts. The Silicon pore optics assembly of XEUS is contained in the mirror spacecraft
while the focal plane instruments are contained in the detector spacecraft, which is maintained at the focus of the
mirror by formation flying. The main requirements for XEUS are to provide a focused beam of X-rays with an
effective aperture of 5 m<sup>2</sup> at 1 keV, 2 m<sup>2</sup> at 7 keV, a spatial resolution better than 5 arcsec, a spectral resolution
ranging from 2 to 6 eV in the 0.1-8 keV energy band, a total energy bandpass of 0.1-40 keV, ultra-fast timing,
and finally polarimetric capabilities. The High Time Resolution Spectrometer (HTRS) is one of the five focal
plane instruments, which comprises also a wide field imager, a hard X-ray imager, a cryogenic spectrometer,
and a polarimeter. The HTRS is unique in its ability to cope with extremely high count rates (up to 2 Mcts/s),
while providing sub-millisecond time resolution and good (CCD like) energy resolution. In this paper, we focus
on the specific scientific objectives to be pursued with the HTRS: they are all centered around the key theme
"Matter under extreme conditions" of the Cosmic Vision science program. We demonstrate the potential of the HTRS observations to probe strong gravity and matter at supra-nuclear densities. We conclude this paper by
describing the current implementation of the HTRS in the XEUS focal plane.
How structures of various scales formed and evolved from the early Universe up to present time is a fundamental
question of astrophysics. EDGE will trace the cosmic history of the baryons from the early generations of massive
stars by Gamma-Ray Burst (GRB) explosions, through the period of galaxy cluster formation, down to the very low
redshift Universe, when between a third and one half of the baryons are expected to reside in cosmic filaments undergoing
gravitational collapse by dark matter (the so-called warm hot intragalactic medium). In addition EDGE, with its
unprecedented capabilities, will provide key results in many important fields. These scientific goals are feasible with a
medium class mission using existing technology combined with innovative instrumental and observational capabilities
by: (a) observing with fast reaction Gamma-Ray Bursts with a high spectral resolution (R ~ 500). This enables the study
of their (star-forming) environment and the use of GRBs as back lights of large scale cosmological structures; (b)
observing and surveying extended sources (galaxy clusters, WHIM) with high sensitivity using two wide field of view
X-ray telescopes (one with a high angular resolution and the other with a high spectral resolution). The mission concept
includes four main instruments: a Wide-field Spectrometer with excellent energy resolution (3 eV at 0.6 keV), a Wide-
Field Imager with high angular resolution (HPD 15") constant over the full 1.4 degree field of view, and a Wide Field
Monitor with a FOV of <sup>1</sup>/<sub>4</sub> of the sky, which will trigger the fast repointing to the GRB. Extension of its energy response
up to 1 MeV will be achieved with a GRB detector with no imaging capability. This mission is proposed to ESA as part
of the Cosmic Vision call. We will briefly review the science drivers and describe in more detail the payload of this
XEUS is the potential successor to ESA's XMM-Newton X-ray observatory and is being proposed in response to the
Cosmic Vision 2015-2025 long term plan for ESA's Science Programme. A new mission configuration was developed
in the last year, accommodating the boundary conditions of a European-led mission with a formation-flying mirror and
detector spacecraft in L2 with a focal length of 35m and an effective area of >5 m<sup>2</sup> at 1 keV. Here the new capabilities
are compared with the key scientific questions presented to the Cosmic Vision exercise: the evolution of large scale
structure and nucleosynthesis, the co-evolution of supermassive black holes and their host galaxies, and the study of
matter under extreme conditions.
The most recent observations of the cosmic microwave background (e.g., WMAP) show that baryons contribute about 4% to the total density of the Universe. However at redshift less than or equal to 1, about half of these baryons have not yet been observed. Cosmological simulations predict that these "missing" baryons should be distributed in filaments, have temperatures of 10<sup>5</sup> to 10<sup>7</sup> K and overdensities of a few to hundred times the average baryon density, forming the so-called Warm-Hot Intergalactic Medium (WHIM). There is increasing evidence from Chandra and XMM-Newton that the WHIM may indeed exist. However it is clear that to map the morphology of the WHIM and to measure its physical conditions, a completely different class of instruments is required. Measuring the WHIM in emission in the soft X-ray band is a promising option. To detect the relatively weak, extended emission of the WHIM, the instrument should have a large grasp (collecting area times field of view), and an energy resolving power of about 500 at 1 keV is required to separate the emission of these large scale filaments from foreground emission.
We discuss a design that includes X-ray mirrors in combination with a large 2D cryogenic detector, which will allow us to map a significant fraction of this gas. Such detector and its read-out based on Frequency Domain Multiplexing, are currently under development at SRON. It seems feasible to build an array of 24 x 24 pixels of TES microcalorimeters with good energy resolution (few eV). This detector will be combined with a mirror design which is based on 2 and 4 reflections and gives a large area (> 500 cm<sup>2</sup>) over a relatively large field of view. A preliminary study of the mission concept indicates that this can be implemented in a relatively small satellite (total weight 650 kg). While the main goal of this satellite will be to map and study the physical properties of the missing baryons, the instrument's large area and large field of view will also result in major progress in related fields.
The Chandra X-ray Observatory carries two transmission gratings on-board, each of them optimized for high- and low-energy photons, respectively. Each grating can be put in the beam behind
Chandra's High-Resolution Mirror Assembly (HRMA); the photons collected with the HRMA and dispersed by the gratings are then collected by one of two imaging detectors located at the
focal of the telescope. The Low-Energy Transmission Grating Spectrometer, LETGS, is sensitive in the range ~2 - 170 Angstroms, and is a powerful tool to study hot plasmas in a variety of astrophysical environments, from stellar coronae to clusters of galaxies. Here we report on the status of this instrument, and we describe some of the scientific results obtained with it.
XEUS is under study by ESA as part of the Horizon 2000+ program to utilize the International Space Station (ISS) for astronomical applications. XEUS will be a long-term x-ray observatory with an initial mirror area of 6 m<sup>2</sup> at 1 keV that will be expanded to 30 m<sup>2</sup> following a visit to the ISS. The 1 keV spatial resolution is expected to be 2-5" half-energy-width. XEUS will consist of separate detector and mirror spacecraft aligned by active control to provide a focal length of 50 m. A new detector spacecraft, complete with the next generation of instruments, will also be added after visiting the ISS. The limiting sensitivity will then be 4×10<sup>-18</sup> erg cm<sup>-2</sup>s<sup>-1</sup>, around 200 times better than XMM-Newton, allowing XEUS to study the properties of the hot baryons and dark matter at high redshift.
A review of the SETI activities in the southern hemisphere over the past three decades is made. A description of the META II program, that is carried out from the Instituto Argentino de Radioastronomia (IAR), and that is continuously scanning the southern skies is described. META (Megachannel Extraterrestrial Assay) is an 8.4 million channels spectrum analyzer with a spectral resolution of 0.05 Hz, working at the 1,420 MHz hydrogen line at the Oak Ridge Harvard radio-observatory and at IAR. A description of the first optical SETI observing program from the southern hemisphere is made. For this purpose a high temporal resolution device called MANIA (Multichannel Analyzer of Nanosecond Intensity Alterations) will be used at the 2.15 m telescope of CASLEO (Complejo AStronomico El LEOncito) in the San Juan province in Argentina.