The Hitomi (ASTRO-H) mission is the sixth Japanese x-ray astronomy satellite developed by a large international collaboration, including Japan, USA, Canada, and Europe. The mission aimed to provide the highest energy resolution ever achieved at E > 2 keV, using a microcalorimeter instrument, and to cover a wide energy range spanning four decades in energy from soft x-rays to gamma rays. After a successful launch on February 17, 2016, the spacecraft lost its function on March 26, 2016, but the commissioning phase for about a month provided valuable information on the onboard instruments and the spacecraft system, including astrophysical results obtained from first light observations. The paper describes the Hitomi (ASTRO-H) mission, its capabilities, the initial operation, and the instruments/spacecraft performances confirmed during the commissioning operations for about a month.
In October 2005, based on a massive response by the Science Community to ESA’s call for themes in space science, a large aperture X-ray Observatory (XRO) was identified as a candidate project for Europe within the frame of the 2015-2025 Cosmic Vision program. Such a mission would represent the natural follow-on to XMM Newton, providing a large aperture X-ray telescope combined with high spectral and time resolution instruments, capable of investigating matter under extreme conditions and the evolution of the early universe.
The paper summarises the results of the most recent ESA internal study activities, leading to an updated mission configuration, with a mirror and a detector spacecraft flying in formation around L2 and a consolidated scientific payload design. The paper also describes the ongoing technology development activities for the payload and for the spacecraft that will play a crucial role in case ESA would decide to develop such a mission.
The Hitomi (ASTRO-H) mission is the sixth Japanese X-ray astronomy satellite developed by a large international collaboration, including Japan, USA, Canada, and Europe. The mission aimed to provide the highest energy resolution ever achieved at E > 2 keV, using a microcalorimeter instrument, and to cover a wide energy range spanning four decades in energy from soft X-rays to gamma-rays. After a successful launch on 2016 February 17, the spacecraft lost its function on 2016 March 26, but the commissioning phase for about a month provided valuable information on the on-board instruments and the spacecraft system, including astrophysical results obtained from first light observations. The paper describes the Hitomi (ASTRO-H) mission, its capabilities, the initial operation, and the instruments/spacecraft performances confirmed during the commissioning operations for about a month.
The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions developed by the Institute of Space and Astronautical Science (ISAS), with a planned launch in 2015. The ASTRO-H mission is equipped with a suite of sensitive instruments with the highest energy resolution ever achieved at E > 3 keV and a wide energy range spanning four decades in energy from soft X-rays to gamma-rays. The simultaneous broad band pass, coupled with the high spectral resolution of ΔE ≤ 7 eV of the micro-calorimeter, will enable a wide variety of important science themes to be pursued. ASTRO-H is expected to provide breakthrough results in scientific areas as diverse as the large-scale structure of the Universe and its evolution, the behavior of matter in the gravitational strong field regime, the physical conditions in sites of cosmic-ray acceleration, and the distribution of dark matter in galaxy clusters at different redshifts.
After more than twelve years in orbit and two years beyond the design lifetime, XMM-Newton continues its near
faultless operations providing the worldwide astronomical community with an unprecedented combination of imaging
and spectroscopic X-ray capabilities together with simultaneous optical and ultra-violet monitoring. The interest from the
scientific community in observing with XMM-Newton remains extremely high with the last annual Announcement of
Observing Opportunity (AO-11) attracting proposals requesting 6.7 times more observing time than was available.
Following recovery from a communications problem in 2008, all elements of the mission are stable and largely trouble
free. The operational lifetime if currently limited by the amount of available hydrazine fuel. XMM-Newton normally
uses reaction wheels for attitude control and fuel is only used when offsetting reaction wheel speed away from limiting
values and for emergency Sun acquisition following an anomaly. Currently, the hydrazine is predicted to last until
around 2020. However, ESA is investigating the possibility of making changes to the operations concept and the onboard
software that would enable lower fuel consumption. This could allow operations to well beyond 2026.
The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions initiated
by the Institute of Space and Astronautical Science (ISAS). ASTRO-H will investigate the physics of the highenergy
universe via a suite of four instruments, covering a very wide energy range, from 0.3 keV to 600 keV.
These instruments include a high-resolution, high-throughput spectrometer sensitive over 0.3–12 keV with
high spectral resolution of ΔE ≦ 7 eV, enabled by a micro-calorimeter array located in the focal plane of
thin-foil X-ray optics; hard X-ray imaging spectrometers covering 5–80 keV, located in the focal plane of
multilayer-coated, focusing hard X-ray mirrors; a wide-field imaging spectrometer sensitive over 0.4–12 keV,
with an X-ray CCD camera in the focal plane of a soft X-ray telescope; and a non-focusing Compton-camera
type soft gamma-ray detector, sensitive in the 40–600 keV band. The simultaneous broad bandpass, coupled
with high spectral resolution, will enable the pursuit of a wide variety of important science themes.
The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions initiated
by the Institute of Space and Astronautical Science (ISAS). ASTRO-H will investigate the physics of the
high-energy universe by performing high-resolution, high-throughput spectroscopy with moderate angular
resolution. ASTRO-H covers very wide energy range from 0.3 keV to 600 keV. ASTRO-H allows a combination
of wide band X-ray spectroscopy (5-80 keV) provided by multilayer coating, focusing hard X-ray
mirrors and hard X-ray imaging detectors, and high energy-resolution soft X-ray spectroscopy (0.3-12 keV)
provided by thin-foil X-ray optics and a micro-calorimeter array. The mission will also carry an X-ray CCD
camera as a focal plane detector for a soft X-ray telescope (0.4-12 keV) and a non-focusing soft gamma-ray
detector (40-600 keV) . The micro-calorimeter system is developed by an international collaboration led
by ISAS/JAXA and NASA. The simultaneous broad bandpass, coupled with high spectral resolution of
ΔE ~7 eV provided by the micro-calorimeter will enable a wide variety of important science themes to be
pursued.
The International X-ray Observatory (IXO) is a candidate mission in the ESA Space Science Programme Cosmic Visions
2015-2025. IXO is being studied as a joint mission with NASA and JAXA. The mission concept and X-ray telescope
accommodation have both been studied in the ESA Concurrent Design Facility. Competitive industrial studies will now
further investigate the issues raised, and will elaborate mission concepts.
In parallel the required technologies are being developed, with the main emphasis under ESA responsibility being
focused on Silicon Pore Optics (SPO). A technology development plan has been made and its implementation is
progressing well.
The paper presents a summary of the ESA system studies of IXO and provides an overview of the related ESA led
technology preparation activities.
The XEUS (X-ray Evolving Universe Spectroscopy) proposal has been recently selected by the science advisory
structure of the European Space Agency as an L-class candidate mission. On this basis, XEUS will undergo an
assessment study, in line with the Cosmic Vision 2015-2025 selection process. The mission would represent a follow-up
to XMM-Newton, providing a next generation X-ray observatory at disposal of the astrophysics community.
The paper provides an overview of the recent study activities performed by ESA, including a critical review of the main
requirements and a discussion on the associated impact at system level. The model payload presently considered for
XEUS is also presented, as well as the technology developments needs.
This paper describes the focal plane instrumentation of the XEUS mission as proposed for ESA's Cosmic Vision
program. Each of the instruments is described in some detail with its performance characteristics given. The
development status of the instrument complement and the items requiring further development are indicated.
A medium size satellite will be launched in the 2010-2011 timeframe into a 600 km equatorial (less than or equal to 5 deg.) orbit from
Kourou or into a less than or equal to 30 deg. orbit from Baikonur as a fallback option. The payload includes eROSITA (extended ROentgen
Survey with an Imaging Telescope Array, MPE, Germany) with 7 Wolter-type telescopes, the wide field X-ray monitor
Lobster (LU, UK), the X-ray concentrator based on Kumakhov optics ART or coded-mask X-ray telescopes as a fallback
(IKI, Russia) and GRB detector (Russian consortium). High particle background on high apogee orbits severely affects
the capabilities of X-ray telescopes to study diffuse emission. For new baseline configuration of the SRG mission a low
earth orbit was selected to circumvent this limitation. The mission will conduct the first all-sky survey with an imaging
telescope in the 2-12 keV band to discover the hidden population of several hundred thousand obscured supermassive
black holes and the first all-sky imaging X-ray time variability survey. In addition to the all-sky surveys it is foreseen to
observe the extragalactic sky with high sensitivity to detect 50 to 100 thousand clusters of galaxies and thereafter to do
follow-up pointed observations of selected sources, in order to investigate the nature of Dark Matter and Dark Energy.
The new SRG mission would thus be a highly significant scientific and technological step beyond Chandra/XMM-Newton
and would provide important and timely inputs for the next generation of giant X-ray observatories like
XEUS/Con-X planned for the 2015-2025 horizon.
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 m2 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.
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. Novel light-weight optics with an effective area of 5 m2 at 1 keV and 2 m2 at 7 keV and 2-5" HEW spatial resolution together with advanced detectors will provide much improved imaging, spectroscopic and timing performances and open new vistas in X-ray astronomy in the post 2015 timeframe. XEUS will allow the study of the birth, growth and spin of the super-massive black holes in early AGN, allow the cosmic feedback between galaxies and their environment to be investigated through the study of inflows and outflows and relativistic acceleration and allow the growth of large scale structures and metal synthesis to be probed using the hot X-ray emitting gas in clusters of galaxies and the warm/hot filamentary structures observable with X-ray absorption spectroscopy. High time resolution studies will allow the Equation of State of supra-nuclear material in neutron stars to be constrained. These science goals set very demanding requirements on the mission design which is based on two formation flying spacecraft launched to the second Earth-Sun Lagrangian point by an Ariane V ECA. One spacecraft will contain the novel high performance optics while the other, separated by the 35 m focal length, will contain narrow and wide field imaging spectrometers and other specialized instruments.
The X-ray Evolving Universe Spectroscopy (XEUS) mission [1,2] is under study by ESA and JAXA in preparation for inclusion in the ESA long term Science Programme (the Cosmic Vision 2015-2025 long-term plan). With very demanding science requirements, missions such as XEUS can only be implemented for acceptable costs, if new technologies and concepts are applied. The identification of the key technologies to be developed is one of the drivers for the early mission design studies, and in the case of XEUS this has led to the development of a novel approach to building X-ray optics for ambitious future high-energy astrophysics missions [3,4]. XEUS is based on a single focal plane formation flying configuration, building on a novel lightweight X-ray mirror technology. With a 50 m focal length and an effective area of 10 m2 at 1 keV this observatory is optimized for studies of the evolution of the X-ray universe at moderate to high redshifts. This paper describes the current status of the XEUS mission design, the accommodation of the large optics, the corresponding deployment sequence and the associated drivers, in particular regarding the thermal design of the ystem. The main results were obtained in two Concurrent Design Facility (CDF) studies and other internal activities at ESTEC.
Gamma ray bursts (GRBs) are the most energetic eruptions known in the Universe. Instruments such as Compton-GRO/BATSE and the GRB monitor on BeppoSAX have detected more than 2700 GRBs and, although observational confirmation is still required, it is now generally accepted that many of these bursts are associated with the collapse of rapidly spinning massive stars to form black holes. Consequently, since first generation stars are expected to be very massive, GRBs are likely to have occurred in significant numbers at early epochs. X-red is a space mission concept designed to detect these extremely high redshifted GRBs, in order to probe the nature of the first generation of stars and hence the time of reionisation of the early Universe. We demonstrate that the gamma and x-ray luminosities of typical GRBs render them detectable up to extremely high redshifts (z ~ 10to30), but that current missions such as HETES and SWIFT operate outside the observational range for detection of high redshift GRB afterglows. Therefore, to redress this, we present a complete mission design from teh science case to the mission architecture and payload, the latter comprising three instruments, namely wide field x-ray cameras to detect high redshift gamma-rays, an x-ray focussing telescope to determine accurate coordinates and extract spectra, and an infrared spectrograph to observe the high redshift optical afterglow. The mission is expected to detect and identify for the first time GRBs with z > 10, thereby providing constraints on properties of the first generation of stars and the history of the early Universe.
XEUS is the potential successor to ESA's XMM-Newton X-ray observatory. Novel light-weight optics with an effective area of 10 m2 at 1 keV and 2-5" HEW spatial resolution together with advanced imaging detectors will provide a sensitivity around 200 times better than XMM-Newton as well as much improved high-energy coverage, and spectroscopic performance. This enormous improvement in scientific capability will open up new vistas in X-ray astronomy. It will allow the detection of massive black holes in the earliest AGN and estimates of their mass, spin and red-shift through their Fe-K line properties. XEUS will study the first gravitationally bound, Dark Matter dominated, systems small groups of galaxies and trace their evolution into today's massive clusters. High-resolution spectroscopy of the hot intra-cluster gas will be used to investigate the evolution of metal synthesis to the present epoch. The hot filamentary structure will be studied using absorption line spectroscopy allowing the mass, temperature and density of the intergalactic medium to be characterized. As well as these studies of the deep universe, the enormous low-energy collecting area will provide a unique capability to investigate bright nearby objects with dedicated high-throughput, polarimetric and time resolution detectors.
Arvind Parmar, G. Hasinger, Monique Arnaud, X. Barcons, D. Barret, A. Blanchard, H. Boehringer, M. Cappi, A. Comastri, T. Courvoisier, A. Fabian, I. Georgantopoulos, R. Griffiths, Nobuyuki Kawai, K. Koyama, K. Makishima, P. Malaguti, K. Mason, C. Motch, Mariano Mendez, T. Ohashi, F. Paerels, L. Piro, J. Schmitt, M. van der Klis, M. Ward
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 m2 at 1 keV that will be expanded to 30 m2 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 4×10-18 erg cm-2s-1, around 200 times better than XMM-Newton, allowing XEUS to study the properties of the hot baryons and dark matter at high redshift.
KEYWORDS: Mirrors, Sensors, Space operations, Dye sensitized solar cells, X-rays, Spatial resolution, Space telescopes, Space mirrors, X-ray optics, X-ray telescopes
The x-ray Evolving Universe Spectroscopy mission (XEUS) is an ambitious project under study by the European Space Agency (ESA), which aims to probe the distant hot universe with comparable sensitivity to NGST and ALMA. The effective optical area and angular resolution required to perform this task is 30m2 and <5" respectively at 1 keV. The single Wolter-I x-ray telescope having these characteristics will be equipped with large area semiconductor detectors and high-resolution cryogenic imaging spectrometers with 2 eV resolution at 1 keV. A novel approach to mission design has been developed, placing the detector instruments on one dedicated spacecraft and the optics on another. The International Space Station (ISS) with the best ever available infrastructure in space will be used to expand the mirror diameter from 4.5 m to 10 m, using robotics and extravehicular activities. The detector spacecraft (DSC) uses solar-electric propulsion to maintain its position while flying in formation with the mirror spacecraft. The detector instruments are protected from straylight and contamination by sophisticated baffles and filters, and employ the earth as a sun shield to make the most sensitive low energy x-ray observations of the heavily red-shifted universe. Detailed approaches, including alternatives to the baseline mission design of XEUS, have been and continue to be addressed, ensuring an efficient concept to be available for the eventual mission implementation. Both the development of the XEUS baseline scenario and complementary work conducted on some alternative mission designs are discussed.
INTEGRAL is ESA's next gamma-ray astronomy mission and is set for launch on 2002 October 17, from Baikonur on a Russian Proton rocket into a 72 hour orbit with an apogee of 150,000 km and a perigee of 10,000 km. INTEGRAL will study some of the most extreme objects in the Universe such as black holes, neutron stars and the mysterious gamma-ray bursts, the most energetic explosions known. The payload consists of two gamma-ray telescopes - SPI, or Spectrometer on INTEGRAL, which will measure gamma-ray energies very precisely and IBIS, or Imager on Board the INTEGRAL Satellite, which will provide very fine images. The sensitivity of INTEGRAL is extended to lower energies by x-ray and optical monitors - the Joint European X-ray Monitor and the Optical Monitoring Camera. The improved imaging and spectral capabilities of INTEGRAL compared to previous gamma-ray missions, as well as the board-band monitoring will provide the scientific community with an unprecedented opportunity to investigate the nature of the extreme Universe.
At the European Space Agency (ESA) X-ray optics are being developed for future astrophysics and planetary missions. The cosmology mission XEUS requires very large effective area X-ray optics which high angular resolution. This implies a large aperture for a single telescope system, which will necessarily require assembly in space from basic mirror modules known as petals. The technology for the implementation of the Wolter-I design is based on the heritage of the XMM-Newton optics, but requires substantial further research and development. With 6 m2 effective area at 1 keV the XEUS optics is initially composed of 32 petals arranged in a circular aperture of 4.5m diameter, compatible with single Arian 5 launch into the XEUS orbit. Utilising the available infrastructure at the International Space Station (ISS) 96 additional petals, organised into 8 segments, are added to XEUS, increasing the effective area to 30 m2. Key aspects of the XEUS optics are therefore low-mass design, industrialisation of the production and ISS compatibility. As a potential optics for a remote sensing X-ray fluorescence spectrometer, extremely low mass Wolter-I optics are being developed. Based on Micro-Channel Plates (MCP), the mirror thickness can be dramatically reduced, making an accommodation on such missions as the Mercury orbiter of BeppiColombo possible. With a resolution of about 1 arcminute and compact construction, such imaging X-ray optics are well matched to modern Si or GaAs based detector arrays and will allow the mapping of the planetary surface in fluorescent X-ray light with unprecedented sensitivity.
Philippe Marty, Juho Schultz, Clemens Bayer, Alexander Fritz, Martin Netopil, Walter Nowotny, Michael Carr, Carlo Ferrigno, Christophe Jean, Walter Koprolin, Jesper Rasmussen, Laura Tanvuia, Ivan Valtchanov, Marcos Bavdaz, Rudolph Much, Arvind Parmar
KEYWORDS: Hard x-rays, X-rays, Space operations, Satellites, Spatial resolution, Sensors, Mirrors, Gallium arsenide, Space telescopes, Data archive systems
The latest all-sky survey in hard X-ray band was performed by the HEAO-1 satellite (13-80 keV) with an angular resolution of 24x48 arcmin. A diffuse hard X-Ray background (HXB) was detected between 3 and 50 keV. The main scientific goal of In.XS is to resolve a large fraction of this HXB into individual sources. As no distortion by Compton up-scattering is seen in the spectrum of the microwave backgroundcite{Mat94}, the hard X-ray background is believed to be mainly due to point sources. Type I Active Galactic Nuclei (AGN) have softer X-ray spectra than the hard X-ray background, so other sources must be considered, like faint Type II or absorbed AGN. These could be distinguished through hard X-ray spectroscopic or hardness ratio observations. Here we present In.XS - a mission concept designed to conduct the first imaging all-sky hard X-ray (2-80 keV)survey. The angular resolution of nearly 1arcmin and good sensitivity at high-energies is provided by the latest multilayer focussing mirrors, with semiconductor-based (GaAs) arrays of detectors. We also describe the mission operations, and how the all-sky survey will be complemented by follow-up pointed observations of selected fields. The good angular resolution will allow correlations and identification with objects seen at other wavelengths. In addition, since a large fraction of the Type II AGN luminosity is emitted in the hard X-ray band, this survey will provide a large unbiased sample of the AGN population. This may provide constraints on AGN evolution through the possible observation of a turnover in deep field source statistics.
KEYWORDS: Sensors, Mirrors, Space operations, X-rays, Spatial resolution, Dye sensitized solar cells, Space telescopes, Telescopes, Space mirrors, X-ray optics
The X-ray Evolving Universe Spectroscopy mission (XEUS) is an ambitious project under study by the European Space Agency (ESA), which aims to probe the distant hot universe with comparable sensitivity to NGST and ALMA. The effective optical area and angular resolution required to perform this task is 30 m2 effective area and <5 inch angular resolution respectively at 1 keV. The single Wolter-I X-ray telescope having these characteristics will be equipped with large area semiconductor detectors and high-resolution cryogenic imaging spectrometers with 2 eV resolution at 1 keV. A novel approach to mission design has been developed, placing the detector instruments on one dedicated spacecraft and the optics on another. The International Space Station (ISS) with the best ever-available infrastructure in space will be used to expand the mirror diameter from 4.5 m to 10 m, by using the European Robotic Arm on the ISS. The detector spacecraft (DSC) uses solar-electric propulsion to maintain its position while flying in formation with the mirror spacecraft. The detector instruments are protected from straylight and contamination by sophisticated baffles and filters, and employing the Earth as a shield to make the most sensitive low energy X-ray observations of the heavily red-shifted universe. After completion of an initial observation phase lasting 5 years, the mirror spacecraft will be upgraded (basically expanded to a full 10 m diameter mirror) at the ISS, while the DSC is replaced by a new spacecraft with a new suite of detector instruments optimised to the full area XEUS mirror. An industrial feasibility study was successfully completed and identified no major problem area. Current activities focus on a full system level study and the necessary technology developments. XEUS is likely to become a truly global mission, involving many of the partners that have teamed up to build the ISS. Japan is already a major partner int the study of XEUS, with ISAS having its main interest in the first DSC.
We describe the design of Lobster-ISS, an X-ray imaging all-sky monitor (ASM) to be flown as an attached payload on the International Space Station. Lobster-ISS is the subject of an ESA Phase-A study which will begin in December 2001. With an instantaneous field of view 162 x 22.5 degrees, Lobster-ISS will map almost the complete sky every 90 minute ISS orbit, generating a confusion-limited catalogue of ~250,000 sources every 2 months. Lobster-ISS will use focusing microchannel plate optics and imaging gas proportional micro-well detectors; work is currently underway to improve the MCP optics and to develop proportional counter windows with enhanced transmission and negligible rates of gas leakage, thus improving instrument throughput and reducing mass. Lobster-ISS provides an order of magnitude improvement in the sensitivity of X-ray ASMs, and will, for the first time, provide continuous monitoring of the sky in the soft X-ray region (0.1-3.5 keV). Lobster-ISS provides long term monitoring of all classes of variable X-ray source, and an essential alert facility, with rapid detection of transient X-ray sources such as Gamma-Ray Burst afterglows being relayed to contemporary pointed X-ray observatories. The mission, with a nominal lifetime of 3 years, is scheduled for launch on the Shuttle c.2009.
The X-ray Evolving Universe Spectroscopy mission (XEUS) is a potential follow-on to ESA's Cornerstone XMM-Newton. XEUS is designed to become a permanent space-based X-ray observatory covering the waveband from 0.5 to 200 angstroms with a sensitivity comparable to the most advanced planned future observations at longer wavelengths, such as NGST, ALMA and FIRST.
XEUS: The X-ray Evolving Universe Spectroscopy mission represents a potential follow-on mission to the ESA XMM cornerstone currently nearing completion. XEUS represents the next logical step forward in x-ray astrophysics after the current set of mission have been launched and completed their operational lives. The development and ultimate success relies heavily on the capability of the International Space Station (ISS). In this paper we describe the key characteristics of the mission including the requirements placed specifically on the ISS and discuss the significant advances in high energy astrophysics expected from such an observatory.
The low energy concentrator system (LECS) is an imaging x- ray spectrometer. I is one of the narrow field instruments onboard the SAX satellite and covers the energy range from 0.1 to 10 keV. The good low energy response of the detector is achieved by using a driftless gas cell and a thin multilayer polyimide foil as an entrance window. SAX was launched on April 30, 1996. Following a two month commissioning phase, the satellite has entered the science verification phase. We report here on the first in-flight data acquired with the LECS. Using back-ground measurements and well known x-ray sources, we present the first results of the in-orbit performance and calibrations an compare them to ground measurements acquired at synchrotron and long beam x-ray sources. After a brief description of the instrument we discuss some aspects related to the ground calibrations. I particular the entrance window characteristics and the particularities of a driftless detector design are reviewed. By correcting for the x-ray absorption depth, we also show how the energy resolution could be enhanced.
The low energy gas scintillation proportional counter (LE-GSPC) is an imaging x-ray spectrometer. It is one of the narrow field instruments on board the SAX satellite and covers the lower energy range from 0.1 to 10 keV. The low energy response of the detector is achieved by using a driftless gas cell and a thin multilayer polyimide foil as entrance window. The overall design of the imaging GSPC for space application is described. Using unit level and system level calibration data, acquired at a synchrotron and a long beam x-ray source, the capabilities both in terms of energy and position resolution are discussed. The overall efficiency of the instrument which includes the mirror's effective area, the entrance windows' transparencies, the detector's efficiency and electronics deadtime are reviewed. Background rejection issues and the experiment's consequent sensitivity to the measurement of cosmic x- ray source spectra are addressed.
In the past decade, gas scintillation proportional counters (GSPCs) have proved their reliability and usefulness in space applications. The combination of high quantum efficiency over a wide energy range, large effective area, good spectral resolution, and high time resolution has given GSPCs a special role in x-ray astronomy. A wide variety of possible configurations makes matching of particular requirements possible. An exact understanding of the physics involved is essential for the further improvement and precise calibration of GSPCs. This paper shows that synchrotron radiation sources, with their continuously variable energies, fluxes, and collimation, provide the ideal tool by which to study the physical processes occurring in GSPCs as well as being perfectly suited for the calibration of such instruments.
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