ESA Science & Technology - Publication Archive

The Wide Field Imager (WFI) of the International X-ray Observatory (IXO) is an X-ray imaging spectrometer based on a large monolithic DePFET (Depleted P-channel Field Effect Transistor) Active Pixel Sensor. Filling an area of 10 x 10 cm² with a format of 1024 x 1024 pixels it will cover a field of view of 18 arcmin. The pixel size of 100 x 100 microns² corresponds to a fivefold oversampling of the telescope's expected 5 arcsec point spread function. The WFI's basic DePFET structure combines the functionalities of sensor and integrated amplifier with nearly Fano-limited energy resolution and high efficiency from 100 eV to 15 keV. The development of dedicated control and amplifier ASICs allows for high frame rates up to 1 kHz and flexible readout modes. Results obtained with representative prototypes with a format of 256 x 256 pixels are presented.

This paper was presented at the SPIE conference on Astronomical Instrumentation 2010 conference.

The Hard X-ray Imager (HXI) is one of the instruments onboard International X-ray Observatory (IXO), to be launched into orbit in 2020s. It covers the energy band of 10-40 keV, providing imaging-spectroscopy with a field of view of 8 x 8 arcmin². The HXI is attached beneath the Wide Field Imager (WFI) covering 0.1-15 keV. Combined with the super-mirror coating on the mirror assembly, this configuration provides observation of X-ray source in wide energy band (0.1-40.0 keV) simultaneously, which is especially important for varying sources. The HXI sensor part consists of the semiconductor imaging spectrometer, using Si in the medium energy detector and CdTe in the high energy detector as its material, and an active shield covering its back to reduce background in orbit. The HXI technology is based on those of the Japanese-lead new generation X-ray observatory ASTRO-H, and partly from those developed for Simbol-X. Therefore, the technological development is in good progress. In the IXO mission, HXI will provide a major assets to identify the nature of the object by penetrating into thick absorbing materials and determined the inherent spectral shape in the energy band well above the structure around Fe-K lines and edges.

This paper was presented at the SPIE conference on Astronomical Instrumentation 2010 conference.

A suspension-mounting scheme is developed for the IXO (International X-ray Observatory) mirror segments in which the figure of the mirror segment is preserved in each stage of mounting. The mirror, first fixed on a thermally compatible strongback, is subsequently transported, aligned and transferred onto its mirror housing. In this paper, we shall outline the requirement, approaches, and recent progress of the suspension mount processes.

This paper was presented at the SPIE conference on Astronomical Instrumentation 2010 conference.

The International X-ray Observatory (IXO) project is the result of a merger between the NASA Con-X and ESA/JAXA XEUS mission concepts. A facility-class mission, IXO will address the leading astrophysical questions in the "hot universe" through its breakthrough optics with 20 times more collecting area at 1 keV than any previous X-ray observatory, its 3 m² collecting area with 5 arcsec angular resolution will be achieved using a 20m focal length deployable optical bench. To reduce risk, two independent optics technologies are currently under development in the U.S. and in Europe. Focal plane instruments will deliver a 100-fold increase in effective area for high-resolution spectroscopy, deep spectral imaging over a wide field of view, unprecedented polarimetric sensitivity, microsecond spectroscopic timing, and high count rate capability. IXO covers the 0.1-40 keV energy range, complementing the capabilities of the next generation observatories, such as ALMA, LSST, JWST, and 30-m ground-based telescopes. These capabilities will enable studies of a broad range of scientific questions such as what happens close to a black hole, how supermassive black holes grow, how large scale structure forms, and what are the connections between these processes? This paper presents an overview of the IXO mission science drivers, its optics and instrumental capabilities, the status of its technology development programs, and the mission implementation approach.

This paper was presented at the SPIE conference on Astronomical Instrumentation 2010 conference.

One of the instruments on the International X-ray Observatory (IXO), under study with NASA, ESA and JAXA, is the X-ray Microcalorimeter Spectrometer (XMS). This instrument, which will provide high spectral resolution images, is based on X-ray micro-calorimeters with Transition Edge Sensor thermometers. The pixels have metallic X-ray absorbers and are read-out by multiplexed SQUID electronics. The requirements for this instrument are demanding. In the central array (40 x 40 pixels) an energy resolution of < 2.5 eV is required, whereas the energy resolution of the outer array is more relaxed (~ 10 eV) but the detection elements have to be a factor 16 larger in order to keep the number of read-out channels acceptable for a cryogenic instrument. Due to the large collection area of the IXO optics, the XMS instrument must be capable of processing high counting rates, while maintaining the spectral resolution and a low deadtime. In addition, an anti-coincidence detector is required to suppress the particle-induced background. In this paper we will summarize the instrument status and performance. We will describe the results of design studies for the focal plane assembly and the cooling systems. Also the system and its required spacecraft resources will be given.

This paper was presented at the SPIE conference on Astronomical Instrumentation 2010 conference.

Different optical designs are under consideration for the International X-ray Observatory (IXO). In this paper we show results of simulations of the segmented shell Wolter-I design, of the Silicon Pore Optics (SPO) conical Wolter-I approximation and of the Silicon based Kirkpatrick-Baez design. We focus particularly on the issue of stray light. When a source is off axis, such that it is not imaged on the detector, some of its light may still be directed by the optics onto the detector plane. Sources close to the pointing direction can thereby introduce an extra background radiation level in the detectors. This phenomenon is investigated by numerical ray tracing of the three designs, yielding detector images of the stray light, and an indication of which part of the mirror that light originates. Results show the similarities and differences of the designs with respect to stray light, and give a quantitative indication of the level of background radiation in different cases. Furthermore, for the Silicon Pore Optics design, two different ways of partially blocking the stray light have been modelled, indicating that a reduction of the stray light can be achieved. In general, the results that have been found indicate that for the simulated set-ups the stray light levels are compliant with the design specifications of the International X-ray Observatory.

This paper was presented at the SPIE conference on Astronomical Instrumentation 2010 conference.

We present a study of the background for the array of microcalorimeters onboard of the International X-ray Observatory space mission. We investigated through simulations the rates at the focal plane of soft and hard particles in L2 orbit. Assuming the presence of an anticoincidence instrument, we derived an estimate of the residual background. The preliminary results reported in this paper are based on a number of simplifications of the actual picture. Efforts to improve the model are on-going.

This paper was presented at the SPIE conference on Astronomical Instrumentation 2010 conference.

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 cm² x 450 microns. 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.

This paper was presented at the SPIE conference on Astronomical Instrumentation 2010 conference.

The technique which combines high resolution spectroscopy with imaging capability is a powerful tool to extract fundamental information in X-ray Astrophysics and Cosmology. TES (Transition Edge Sensors)-based microcalorimeters match at best the requirements for doing fine spectroscopy and imaging of both bright (high count rate) and faint (poor signal-to-noise ratio) sources. For this reason they are considered among the most promising detectors for the next high energy space missions and are being developed for use on the focal plane of the IXO (International X-ray Observatory) mission. In order to achieve the required signal-to-noise ratio for faint or diffuse sources it is necessary to reduce the particle-induced background by almost two orders of magnitude. This reduction can only be achieved by adopting an active anticoincidence technique. In this paper, we will present a novel anticoincidence detector based on a TES sensor developed for the IXO mission. The pulse duration and the large area of the IXO TESarray (XMS X-ray Microcalorimeter Spectrometer) require a proper design of the anticoincidence detector. It has to cover the full XMS area, yet delivering a fast response. We have therefore chosen to develop it in a four-pixel design. Experimental results from the large-area pixel prototypes will be discussed, also including design considerations.

This paper was presented at the SPIE conference on Astronomical Instrumentation 2010 conference.

The requirements for the IXO (International X-ray Observatory) telescope are very challenging in respect of angular resolution and effective area. Within a clear aperture with 1.7 m > R > 0.25 m that is dictated by the spacecraft envelope, the optics technology must be developed to satisfy simultaneously requirements for effective area of 2.5 m² at 1.25 keV, 0.65 m² at 6 keV and 150 cm² at 30 keV. The reflectivity of the bare mirror substrate materials does not allow these requirements to be met. As such the IXO baseline design contains a coating layout that varies as a function of mirror radius and in accordance with the variation in grazing incidence angle. The higher energy photon response is enhanced through the use of depth-graded multilayer coatings on the inner radii mirror modules. In this paper we report on the first reflectivity measurements of wedged ribbed silicon pore optics mirror plates coated with a depth graded W/Si multilayer. The measurements demonstrate that the deposition and performance of the multilayer coatings is compatible with the SPO production process.

This paper was presented at the SPIE conference on Astronomical Instrumentation 2010 conference.

We describe the experimental apparatus in use to test an off-plane reflection grating for the soft x-ray (0.3-1.0 keV) bandpass. The grating is a prototype for the X-ray Grating Spectrometer on the International X-ray Observatory (IXO). It has holographically-ruled radial grooves to match the converging beam of a 6.5 m focal length telescope. Laboratory tests are ongoing, with ray tracing indicating that a resolution (DeltaE/E) >3,000 is achievable across the 0.3-1.0 keV bandpass- the requirement to achieve IXO science goals.

This paper was presented at the SPIE conference on Astronomical Instrumentation 2010 conference.

The IXO/XMS instrument baseline is an array of TES sensors. Alternatively, we are now developing a micro-calorimeter array based on Silicon doped sensors. Our strength stands in a very low power consumption at 50 mK, allowing more than 4000 readout channels in the limited power budget of the IXO/XMS cryostat, for a Field of View as large as 6'x6' square while keeping the same spectral resolution. In parallel, we develop the cold (2-4K) frontend electronics based on High Electron Mobility Transistors (GaAlAs/GaAs) and SiGe ASIC electronics to readout, amplify and multiplex the signals. We present the status of our development and our current design study.

This paper was presented at the SPIE conference on Astronomical Instrumentation 2010 conference.

One of the key unresolved problems in the study of space plasmas is to explain the production of energetic electrons as magnetic field lines "reconnect" and release energy in an explosive manner. Recent observations suggest possible roles played by small-scale magnetic islands in the reconnection region, but their precise roles and the exact mechanism of electron energization have remained unclear. Here we show from two-dimensional particle-in-cell simulations that secondary islands generated in the reconnection region indeed produce energetic electrons. We found that when electrons are trapped inside the islands, they are energized continuously by the reconnection electric field prevalent in the reconnection diffusion region. Applications to observations in the Earth's magnetotail are briefly discussed.

Current efforts in observational cosmology are focused on characterizing the mass-energy content of the universe. We present results from a geometric test based on strong lensing in galaxy clusters. Based on Hubble Space Telescope images and extensive ground-based spectroscopic follow-up of the massive galaxy cluster Abell 1689, we used a parametric model to simultaneously constrain the cluster mass distribution and dark energy equation of state. Combining our cosmological constraints with those from X-ray clusters and the Wilkinson Microwave Anisotropy Probe 5-year data gives Omega_m = 0.25 ±0.05 and w_x = -0.97 ±0.07, which are consistent with results from other methods. Inclusion of our method with all other available techniques brings down the current 2-sigma contours on the dark energy equation-of-state parameter w_x by ~30%.

Magnetic reconnection plays a key role in the circulation of plasma through the Earth's magnetosphere. As such, the Earth's magnetotail is an excellent natural laboratory for the study of reconnection and in particular the diffusion region. To address important questions concerning observational occurrence rates and average properties, the Cluster data set from 2001-2005 has been systematically examined for encounters with reconnection X lines and ion diffusion regions in the Earth's magnetotail. This survey of 175 magnetotail passes resulted in a sample of 33 correlated field and flow reversals. Eighteen events exhibited electric and magnetic field perturbations qualitatively consistent with the predictions of antiparallel Hall reconnection and could be identified as diffusion region encounters. The magnitudes of both the Hall magnetic and electric field were found to vary from event to event. When normalized against the inflow magnetic field and the current sheet number density the average peak Hall magnetic field was found to be 0.39 ± 0.16, the average peak Hall electric field was found to be 0.33 ± 0.18, and the average out of plane (reconnection) electric field was found to be <0.04. Good quantitative agreement was found between these results and a large, appropriately renormalized particle-in-cell simulation of reconnection. In future missions, the magnitude of the total DC electric field may be a useful tool for automatically identifying ion diffusion region encounters.

The assessment study of a Space-Time Explorer (STE) mission has been performed at ESA's Concurrent Design Facility (CDF) and ran from 15 June to 16 July 2010. The internal final presentation has been prepared by the STE/CDF team and summarizes the outcome of the STE assessment study. This presentation can be downloaded below as a PDF (link to publication). Contents of presentation:

- Introduction - Background - Mission analysis - Systems - Payload - Optical Link - Communication - Power subsystems - Mechanisms - AOCS

- Propulsion - Ground Segment and Operations - Radiation - Data Handling System - Programmatics / AIV - Risk - Thermal - Structures - Configuration - Conclusions

A summary of the STE mission concept and science goals is on the "Space-Time Explorer (STE)" page, linked form the right-hand menu.

The Fundamental Physics Roadmap Advisory Team (FPR-AT) has been convened by ESA in order to draw up recommendations on the scientific and technological roadmap necessary to lead Europe toward the realization of future space missions in the framework of the Cosmic Vision 2015-2025 plan in the field of fundamental physics.

This roadmap document is the final report prepared by the FPR-AT, after an in-depth consultation with the European scientific community.

Content:

Fundamental Physics Roadmap
Executive summary
A. Introduction
B. The scientific field covered by this roadmap: present status
	B-1.	Overview
	B-2.	Multiple connections
	B-3.	A rich space program and associated experiments
	B-4.	Ground vs space: future prospects on ground versus prospective missions
C. A roadmap for fundamental physics in space
	C-1.	Key science objectives
	C-2.	Priorities for the space program
	C-3.	Technology
	C-4.	The community and its organization
	C-5.	A set of recommendations

In this paper, we report observations from a Cluster satellite showing that ULF wave occurred in the outer boundary of a plasmaspheric plume on September 4, 2005. The band of observed ULF waves is between the He⁺ ion gyrofrequency and O⁺ ion gyrofrequency at the equatorial plane, implying that those ULF waves can be identified as EMIC waves generated by ring current ions in the equatorial plane and strongly affected by rich cold He+ ions in plasmaspheric plumes. During the interval of observed EMIC waves, the footprint of Cluster SC3 lies in a subauroral proton arc observed by the IMAGE FUV instrument, demonstrating that the subauroral proton arc was caused by energetic ring current protons scattered into the loss cone under the Ring Current (RC)-EMIC interaction in the plasmaspheric plume. Therefore, the paper provides a direct proof that EMIC waves can be generated in the plasmaspheric plume and scatter RC ions to cause subauroral proton arcs.

The SAR has been tasked by the JWST Mission Office to investigate what science cases will be of relevance for the general community in the timeframe 2012-2015, uniquely exploiting the JWST capabilities. These science cases are in addition to, and not a repetition of, the science drivers developed in the JWST Science Requirements Document (SRD). They do not necessarily represent 'drivers', but are a representative sample of science that the 'community' considers important to pursue with JWST in the indicated timeframe, and in addition to the fundamental science described in the SRD.

The JamesWebb Space Telescope (JWST) is a large (6.6 m), cold (<50 K), infrared (IR)- optimized space observatory that will be launched early in the next decade into orbit around the second Earth-Sun Lagrange point. The observatory will have four instruments: a near-IR camera, a near-IR multiobject spectrograph, and a tunable filter imager will cover the wavelength range, 0.6 < l < 5.0 microns, while the mid-IR instrument will do both imaging and spectroscopy from 5.0 < l < 29 microns.