Publication archive

Publication archive

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.

Published: 31 July 2010

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.

Published: 31 July 2010

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.

Published: 31 July 2010

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.

Published: 31 July 2010

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.

Published: 31 July 2010

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.

Published: 30 July 2010
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.
Published: 22 August 2010
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 Omegam = 0.25 ±0.05 and wx = -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 wx by ~30%.
Published: 20 August 2010
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.
Published: 15 August 2010
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.
Published: 17 July 2010
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

Published: 27 July 2010
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.
Published: 14 April 2010
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.
Published: 15 November 2005

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.

Published: 15 November 2006
The James Webb Space Telescope (Gardner et al. 2006) will be capable of characterizing extrasolar planets to significantly greater sensitivity than the current Spitzer detections (Charbonneau et al. 2005, Deming et al. 2005, 2006). In combination with ground-based transit surveys and scientific results from the Kepler and Corot missions, JWST will be able to address the detailed physical characterization of up to 250 exosolar planets (Mountain et al. 2006; Beichman et al. 2006). Transit studies of exosolar planets are currently unique in providing measurements that permit comparative exoplanetology.
Published: 15 November 2007
The James Webb Space Telescope (JWST) will be an exciting, highly capable tool, able to make important contributions to studies of stellar populations in nearby galaxies, including our own. JWST observations will contribute to: (1) the study of the star formation histories of nearby galaxies, exploiting the large lever arm provided by visibleinfrared colors; (2) the derivation of the properties of stellar populations from the study of the bright red stellar component out to the Virgo cluster and beyond; and (3) the derivation of the white dwarf cooling sequence age of globular clusters in the Milky Way from the study of deep visible red color magnitude diagrams.
Published: 23 October 2008
The James Webb Space Telescope is a large (25 m2), cold (<50 K), infrared (IR)-optimized space observatory that will be launched during 2013. It is the successor to the Hubble and Spitzer Space Telescopes. The observatory has four instruments: a near-IR camera, a near-IR multi-object spectrograph, and a tunable filter imager will operate within the wavelength range, 0.6 < l < 5.0 microns, while the mid-IR instrument will provide both imaging and spectroscopy over the 5.0 < l < 28.5 microns spectrum.
Published: 15 November 2009
We discuss the recent progress on stellar populations provided by the influx of high sensitivity infrared photometry measurements using the Spitzer SAGE survey of the Large Magellanic Cloud as an example. We discuss the important role JWST will play in expanding such studies out to the local volume of galaxies (~10 Mpc) and its synergy with concurrent missions. In addition to observational capabilities, we will need theoretical tools to further this field in the next decade.
Published: 15 November 2009
JWST provides capabilities unmatched by other telescopic facilities in the near to mid infrared part of the electromagnetic spectrum. Its combination of broad wavelength range, high sensitivity and near diffraction-limited imaging around two microns wavelength make it a high value facility for a variety of Solar System targets. Beyond Neptune, a class of cold, large bodies that include Pluto, Triton and Eris exhibits surface deposits of nitrogen, methane, and other molecules that are poorly observed from the ground, but for which JWST might provide spectral mapping at high sensitivity and spatial resolution difficult to match with the current generation of ground-based observatories. The observatory will also provide unique sensitivity in a variety of near and mid infrared windows for observing relatively deep into the atmospheres of Uranus and Neptune, searching there for minor species. It will examine the Jovian aurora in a wavelength regime where the background atmosphere is dark. Special provision of a subarray observing strategy may allow observation of Jupiter and Saturn over a larger wavelength range despite their large surface brightnesses, allowing for detailed observation of transient phenomena including large scale storms and impact-generation disturbances. JWSTs observations of Saturns moon Titan will overlap with and go beyond the 2017 end-of-mission for Cassini, providing an important extension to the time-series of meteorological studies for much of northern hemisphere summer. It will overlap with a number of other planetary missions to targets for which JWST can make unique types of observations. JWST provides a platform for linking solar system and extrasolar planet studies through its unique observational capabilities in both arenas.
Published: 09 March 2010
Determination of the physical and chemical properties of planetary systems is the main objective of the planetary systems and the origins of life scientific theme of the James Webb Space Telescope (JWST). This white paper summarizes the missions capabilities for direct detection and study of exoplanets and circumstellar material (>0.1" from parent star), planets and other objects in our own Solar System, and corresponding scientific advances expected from JWST in the next decade.
Published: 15 November 2009
14-Jul-2020 14:40 UT

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