The Energetic X-ray Imaging Survey Telescope (EXIST) is designed to i) use the birth of stellar mass black holes, as
revealed by cosmic Gamma-Ray Bursts (GRBs), as probes of the very first stars and galaxies to exist in the Universe.
Both their extreme luminosity (~10<sup>4</sup> times larger than the most luminous quasars) and their hard X-ray detectability over
the full sky with wide-field imaging make them ideal "back-lights" to measure cosmic structure with X-ray, optical and
near-IR (nIR) spectra over many sight lines to high redshift. The full-sky imaging detection and rapid followup narrowfield
imaging and spectroscopy allow two additional primary science objectives: ii) novel surveys of supermassive black
holes (SMBHs) accreting as very luminous but rare quasars, which can trace the birth and growth of the first SMBHs as
well as quiescent SMBHs (non-accreting) which reveal their presence by X-ray flares from the tidal disruption of
passing field stars; and iii) a multiwavelength Time Domain Astrophysics (TDA) survey to measure the temporal
variability and physics of a wide range of objects, from birth to death of stars and from the thermal to non-thermal
Universe. These science objectives are achieved with the telescopes and mission as proposed for EXIST described here.
The <i>EXIST</i> mission has been recently re-designed prior to being proposed to the ASTRO2010 Decadal Survey. One of
the most recent improvements has been the addition of a third instrument consisting of a powerful Soft X-ray Imager
(SXI) that will study in detail and help characterizing the high energy sources detected by the High Energy Telescope
(HET). The <i>EXIST</i> concept fully exploits the heritage of Swift in the fast follow-up of transients and in particular GRBs,
with 10 to 20 times more sensitivity in the high energy band (from 0.2 to 600 keV) and exceptional performance in the
near-IR/optical provided by the Infrared Telescope (IRT). SXI has an important role in extending by more than one
decade in energy, down to the soft X-rays the coverage of HET. Such combination will be fully exploited when
performing pointed observations. Within the <i>EXIST</i> follow-up program, foreseen during the second part of the mission,
SXI and HET will be able to collect high quality spectra for thousands of sources covering the energy range 0.1-
hundreds keV. Furthermore, while working in survey mode SXI will cover about half the sky in 2 years and will be able
to improve the location accuracy of many faint HET sources (reducing the positional uncertainty from 20 arcsec to ~ 1-2
arcsec). In this paper we will address the performance and the main scientific contributions expected from SXI.
The hard X-ray sky now being studied by <i>INTEGRAL</i> and <i>Swift</i> and soon by <i>NuSTAR</i> is rich with energetic phenomena
and highly variable non-thermal phenomena on a broad range of timescales. The High Energy Telescope (HET) on the
proposed Energetic X-ray Imaging Survey Telescope (<i>EXIST</i>) mission will repeatedly survey the full sky for rare and
luminous hard X-ray phenomena at unprecedented sensitivities. It will detect and localize (<20", at 5σ threshold) X-ray
sources quickly for immediate followup identification by two other onboard telescopes - the Soft X-ray imager (SXI)
and Optical/Infrared Telescope (IRT). The large array (4.5 m<sup>2</sup>) of imaging (0.6 mm pixel) CZT detectors in the HET, a
coded-aperture telescope, will provide unprecedented high sensitivity (~0.06 mCrab Full Sky in a 2 year continuous
scanning survey) in the 5 - 600 keV band. The large field of view (90° × 70°) and zenith scanning with alternating-orbital
nodding motion planned for the first 2 years of the mission will enable nearly continuous monitoring of the full
sky. A 3y followup pointed mission phase provides deep UV-Optical-IR-Soft X-ray and Hard X-ray imaging and
spectroscopy for thousands of sources discovered in the Survey. We review the HET design concept and report the
recent progress of the CZT detector development, which is underway through a series of balloon-borne wide-field hard
X-ray telescope experiments, <i>ProtoEXIST</i>. We carried out a successful flight of the first generation of fine pixel large
area CZT detectors (<i>ProtoEXIST1</i>) on Oct 9, 2009. We also summarize our future plan (<i>ProtoEXIST2</i> & <i>3</i>) for the
technology development needed for the HET.
The Energetic X-ray Imaging Survey Telescope (EXIST) mission, submitted to the Decadal Survey, is a
multiwavelength observatory mainly devoted to the study of Super Massive Black Holes, Gamma Ray Bursts and other
transient sources. The set of instruments foreseen for EXIST includes a soft x-ray telescope (SXI), proposed as a
contribution of the Italian Space Agency (ASI).
We present the baseline design of the X-Ray camera for SXI telescope, that we have finalized under ASI contract. The
camera is based on a focal plane detector consisting of a 450 μm thick silicon pixel sensor sensitive, with high QE, in the
full SXI range (0.1-10 KeV), and capable of high energy resolution when operated in photon counting mode (E/dE ~ 47
at 6 keV), frame rate ~ 100-200 frames/s (enabling timing in the ms range), and spatial resolution matching the optical
characteristics of the mirror module. We provide an overview of the mechanical, thermal and electrical concept of the
The Energetic X-ray Imaging Survey Telescope (EXIST) will continuously survey the full sky in scanning mode for 2-
years followed by a 3-years pointing phase. The mission includes three instruments: a High Energy coded mask
Telescope; a 1.1m aperture optical-IR Telescope; and a Soft X-ray Imager (SXI), sensitive in the 0.1-10 keV band. SXI
is proposed as a contribution of ASI-Italy, fully developed by Italian institutes. Here we will present the optical and
mechanical design of the SXI mirror module, that includes also a pre-collimator and a magnetic diverter to ensure a low
background on the detector. In particular we will describe the mirror module characteristics in term of effective area,
imaging capability, thermal requirement and mechanical properties. The current optical design foresees 26 shells
providing an effective area comparable to one XMM-Newton mirror module up to 3 keV. The realization of these shells
is based on the well-proven Nickel replication-process technology.
The EXIST observatory planned for launch in the next decade will carry outstanding contributions in both Galactic and
Extragalactic science with a sensitivity about 10-20 better respect to the flown hard X-ray missions and full sky survey
capability. Designed mainly for the survey of SMBH and transients, thanks to the wide field of view (~70x90deg) and
large effective area of the High Energy Telescope (HET), the study of spectra and variability at all timescales of all types
of Galactic sources will be made possible. EXIST will be also capable to study in detail the Galactic Center (GC) in the
hard X-rays. This crowded region as observed recently by Chandra, Integral and Swift has been found to possibly host a
high number of high energy sources. In this work we report on the capabilities of EXIST to image the GC region and to
detect and characterize the different classes of sources on the basis of their known spectral and variability properties.
EXIST will perform the crucial observation tests to study the emission from Sgr A*, using the simultaneous observations
of IR and X-ray flares, searching for periodicity to study the Keplerian flow with NIR and/or X QPO, confirm or not the
high energy counterpart of SgrA* detected by INTEGRAL and define the spectral shape of the high energy tail. Finally,
EXIST can effectively and continuously monitor spectra from Sgr B2 to confirm the correlation of the iron line emission
with the hard X-ray continuum and establish its origin.
We report on the development of a 3D position sensitive prototype suitable as focal plane detector for Laue lens
telescope. The basic sensitive unit is a drift strip detector based on a CZT crystal, (~19×8 mm<sup>2</sup> area, 2.4 mm thick),
irradiated transversally to the electric field direction. The anode side is segmented in 64 strips, that divide the crystal in 8
independent sensor (pixel), each composed by one collecting strip and 7 (one in common) adjacent drift strips. The drift
strips are biased by a voltage divider, whereas the anode strips are held at ground. Furthermore, the cathode is divided in
4 horizontal strips for the reconstruction of the third interaction position coordinate. The 3D prototype will be made by
packing 8 linear modules, each composed by one basic sensitive unit, bonded on a ceramic layer. The linear modules
readout is provided by a custom front end electronics implementing a set of three RENA-3 for a total of 128 channels.
The front-end electronics and the operating logics (in particular coincidence logics for polarisation measurements) are
handled by a versatile and modular multi-parametric back end electronics developed using FPGA technology.
Laue lenses are an emerging technology based on diffraction in crystals that allows the concentration of soft
gamma rays. This kind of optics that works in the 100 keV - 1.5 MeV band can be used to realize an highsensitivity
and high-angular resolution telescope (in a narrow field of view). This paper reviews the recent
progresses that have been done in the development of efficient crystals, in the design study and in the modelisation
of the answer of Laue lenses. Through the example of a new concept of 20 m focal length lens focusing in the 100
keV - 600 keV band, the performance of a telescope based on a Laue lens is presented. This lens, uses the most
efficient mosaic crystals in each sub-energy range in order to yield the maximum reflectivity. Imaging capabilities
are investigated and shows promising results.
The Energetic X-ray Imaging Survey Telescope (EXIST) is a mission that has been studied for the NASA Physics of the
Cosmos Program. EXIST will continuously survey the full sky by scanning for 2-years (with 2-3 interruptions per day
for GRB follow-up) followed by a 3-years pointing phase. The mission includes three instruments: a High Energy coded
mask Telescope; a 1.1m aperture optical-IR Telescope; and a Soft X-ray Imager (SXI), sensitive in the 0.1-10 keV band.
SXI is proposed as a contribution of ASI-Italy, fully developed by Italian institutes. The current optical design foresees
26 shells providing an effective area comparable to one XMM-Newton mirror module up to 3 keV and somewhat lower
from 3 to 10 keV. The realization of these shells is based on the well-proven Nichel replication-process technology. Here
we will present the optical design of the SXI mirror module and describe its characteristics in term of effective area and
imaging capability, summarizing also the characteristics of the full SXI telescope.
The SXI telescope is one of the three instruments on board EXIST, a multiwavelenght observatory in charge of
performing a global survey of the sky in hard X-rays searching for Supermassive Black Holes. One of the primary
objectives of EXIST is also to study with unprecedented sensitivity the most unknown high energy sources in
the Universe, like high redshift GRBs, which will be pointed promptly by the Spacecraft by autonomous trigger
based on hard X-ray localization on board. The recent addition of a soft X-ray telescope to the EXIST payload
complement, with an effective area of 950 cm<sup>2</sup> in the energy band 0.2-3 keV and extended response up to 10 keV
will allow to make broadband studies from 0.1 to 600 keV. In particular, investigations of the spectra components
and states of AGNs and monitoring of variability of sources, study of the prompt and afterglow emission of GRBs
since the early phases, which will help to constrain the emission models and finally, help the identification of
sources in the EXIST hard X-ray survey and the characterization of the transient events detected. SXI will also
perform surveys: a scanning survey with sky coverage ~ 2 π and limiting flux of ~ 5 × 10<sup>-14</sup> cgs plus other
serendipitous. We give an overview of the SXI scientific performance and also describe the status of its design
emphasizing how it has been derived by the scientific requirements.
The science drivers for a new generation soft gamma-ray mission are naturally focused on the detailed study of
the acceleration mechanisms in a variety of cosmic sources. Through the development of high energy optics in the
energy energy range 0.05-1 MeV it will be possible to achieve a sensitivity about two orders of magnitude better
than the currently operating gamma-ray telescopes. This will open a window for deep studies of many classes of
sources: from Galactic X-ray binaries to magnetars, from supernova remnants to Galaxy clusters, from AGNs
(Seyfert, blazars, QSO) to the determination of the origin of the hard X-/gamma-ray cosmic background, from
the study of antimatter to that of the dark matter. In order to achieve the needed performance, a detector with
mm spatial resolution and very high peak efficiency is needed. The instrumental characteristics of this device
could eventually allow to detect polarization in a number of objects including pulsars, GRBs and bright AGNs. In
this work we focus on the characteristics of the focal plane detector, based on CZT or CdTe semiconductor sensors
arranged in multiple planes and viewed by a side detector to enhance gamma-ray absorption in the Compton
regime. We report the preliminary results of an optimization study based on simulations and laboratory tests,
as prosecution of the former design studies of the GRI mission which constitute the heritage of this activity.
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
The success of the SWIFT/BAT and INTEGRAL missions has definitely opened a new window for follow-up
and deep study of the transient gamma-ray sky. This now appears as the access key to important progresses in
the area of cosmological research and deep understanding of the physics of compact objects. To detect in near
real-time explosive events like Gamma-Ray bursts, thermonuclear flashes from Neutron Stars and other types of
X-ray outbursts we have developed a concept for a wide-field gamma-ray coded mask instrument working in the
range 8-200 keV, having a sensitivity of 0.4 ph cm<sup>−2</sup> s<sup>−1</sup> in 1 s (15-150 keV) and arcmin location accuracy over
a sky region as wide as 3 sr. This scientific requirement can be achieved by means of two large area, high spatial
resolution CZT detection planes made of arrays of relatively large (~ 1 cm<sup>2</sup>) crystals, which are in turn read
out as matrices of smaller pixels. To achieve such a wide Field-Of-View the two units can be placed at the sides
of a S/C platform serving a payload with a complex of powerful X-ray instruments, as designed for the EDGE
mission. The two units will be equipped with powerful signal read out system and data handling electronics,
providing accurate on-board reconstruction of the source positions for fast, autonomous target acquisition by
the X-ray telescopes.
In the context of R&D studies financed by the Italian Space Agency (ASI), a feasibility study to evaluate the Italian
Industry interest in medium-large scale production of enhanced CZT detectors has been performed by an Italian
Consortium. The R&D investment aims at providing in-house source of high quality solid state spectrometers for Space
Astrophysics applications. As a possible spin-off industrial applications to Gamma-ray devices for non-destructive
inspections in medical, commercial and security fields have been considered by ASI. The short term programme mainly
consists of developing proprietary procedures for 2-3" CZT crystals growth, including bonding and contact philosophy,
and a newly designed low-power electronics readout chain. The prototype design and breadboarding is based on a fast
signal AD conversion with the target in order to perform a new run for an already existing low-power (<0.7 mW/pixel)
ASIC. The prototype also provides digital photon energy reconstruction with particular care for multiple events and
polarimetry evaluations. Scientific requirement evaluations for Space Astrophysics Satellite applications have been
carried out in parallel, targeted to contribute to the ESA Cosmic Vision 2015-2025 Announcement of Opportunity.
Detailed accommodation studies are undergoing, as part of this programme, to size a "Large area arcsecond angular
resolution Imager" for the Gamma Ray Imager satellite (Knödlseder et al., this conference).and a new Gamma-ray Wide
Field Camera for the "EDGE" proposal (Piro et al., this conference). Finally, an extended market study for cost analysis
evaluation in view of the foreseen massive detector production has been performed.
The development of formation flying technology in space has opened a new window for astronomy at hard X-γ-ray
wavelenghts, allowing observations with unprecedented angular resolution (location accuracy of the order of few
arcsec). This has stimulated the development of new concepts for imaging instruments: on one side, the focusing
telescopes like γ-ray lens, using small,well shielded detector volumes, on the other side very large area γ-ray
imagers, both allowing a big step in sensitivity. We report on a study for the concept of a large area (1 square
meter), narrow field coded mask telescope with arcsec imaging capability, based on CZT detector technology
and active collimation system, made of Si microstrip detector modules and operating in the energy band 15-500
keV. Feasibility and performance characteristics are discussed as well as possible geometric configurations and
background suppression schemes, in the light of data obtained from INTEGRAL/IBIS and other CdTe/CZT
instruments currently in space.
The energy range above 50 keV is important for the study of many open problems in high energy astrophysics such as,
non thermal mechanisms in SNR, the study of the high energy cut-offs in AGN spectra, and the detection of nuclear and
annihilation lines. In the framework of the definition of a new mission concept for hard X and soft gamma ray (GRI-
Gamma Ray Imager) for the next decade, the use of Laue lenses with broad energy band-passes from 100 to 1000 keV is
under study. This kind of instruments will be used for deep study the hard X-ray continuum of celestial sources. This
new telescope will require focal plane detectors with high detection efficiency over the entire operative range, an energy
resolution of few keV at 500 keV and a sensitivity to linear polarization. We describe a possible configuration for the
focal plane detector based on CdTe/CZT pixelated layers stacked together to achieve the required detection efficiency at
high energy. Each layer can either operate as a separate position sensitive detector and a polarimeter or together with
other layers in order to increase the overall full energy efficiency. We report on the current state of art in high Z
spectrometers development and on some activities undergoing. Furthermore we describe the proposed focal plane option
with the required resources and an analytical summary of the achievable performance in terms of efficiency and
We present a mission designed to address two main themes of the ESA Cosmic Vision Programme: the Evolution of the Universe and its Violent phenomena. ESTREMO/WFXRT is based on innovative instrumental and observational approaches, out of the mainstream of observatories of progressively increasing area, i.e.: Observing with fast reaction transient sources, like GRB, at their brightest levels, thus allowing high resolution spectroscopy. Observing and surveying through a X-ray telescope with a wide field of view and with high sensitivity extended sources, like cluster and Warm Hot Intragalactic Medium (WHIM). ESTREMO/WFXRT will rely on two cosmological probes: GRB and large scale X-ray structures. This will allow measurements of the dark energy, of the missing baryon mass in the local universe, thought to be mostly residing in outskirts of clusters and in hot filaments (WHIM) accreting onto dark matter structures, the detection of first objects in the dark Universe, the history of metal formation. The key asset of ESTREMO/WFXRT with regard to the study of Violent Universe is the capability to observe the most extreme objects of the Universe during their bursting phases. The large flux achieved in this phase allows unprecedented measurements with high resolution spectroscopy. The mission is based on a wide field X-ray/hard X-ray monitor, covering >1/4 of the sky, to localize transients; fast (min) autonomous follow-up with X-ray telescope (2000 cm<sup>2</sup>) equipped with high resolution spectroscopy transition edge (TES) microcalorimeters (2eV resolution below 2 keV) and with a wide field (1°) for imaging with 10" resolution (CCD) extended faint structures and for cluster surveys. A low background is achieved by a 600 km equatorial orbit. The performances of the mission on GRB and their use as cosmological beacons are presented and discussed.
The outstanding scientific performances of IBIS, Imager on Board INTEGRAL, has encouraged preliminary feasibility studies on new Gamma Ray instruments. We considered both a Wide Field Camera for transient event detection and fast automatic sky localisation and a high resolution imager. According to the basic scientific requirements, i.e. to operate with good sensitivity (1mCrab/day) and spatial resolution (from arcmin to arcsec) on a wide energy range (5 to 500 keV), these studies consider large detector area (from 1 to several m<sup>2</sup>) and a high number (~50000) of thick (≥ 5mm) pixels. Recent achievements already obtained by INTEGRAL, and initially showed by SWIFT, have validated the CdTe/CZT detector performances in terms of good spatial resolution, detection efficiency, energy resolution and low noise at room temperature. We have started a study to solve peculiar problems affecting this kind of detectors (e.g. response dependent on the interaction depth and multiple hit events) using a digital approach to photon reconstruction. This also facilitates operations like pixel to pixel equalisation and background rejection. The detector electronic chain thus includes a minimal analog stage for charge pre-amplification, coupled to a flash ADC for waveform digitalisation at a high time resolution sampling, and a powerful, FPGA based digital processing unit, devoted to waveform elaboration. Such a design should also help in optimising the telemetry flux and allow polarimetry evaluation on multiple events.
The mission concept MAX is a space borne crystal diffraction telescope, featuring a broad-band Laue lens optimized for the observation of compact sources in two wide energy bands of high astrophysical relevance. For the first time in this domain, gamma-rays will be focused from the large collecting area of a crystal diffraction lens onto a very small detector volume. As a consequence, the background noise is extremely low, making possible unprecedented sensitivities. The primary scientific objective of MAX is the study of type Ia supernovae by measuring intensities, shifts and shapes of their nuclear gamma-ray lines. When finally understood and calibrated, these profoundly radioactive events will be crucial in measuring the size, shape, and age of the Universe. Observing the radioactivities from a substantial sample of supernovae and novae will significantly improve our understanding of explosive nucleosynthesis. Moreover, the sensitive gamma-ray line spectroscopy performed with MAX is expected to clarify the nature of galactic microquasars (e<sup>+</sup>e<sup>-</sup> annihilation radiation from the jets), neutrons stars and pulsars, X-ray Binaries, AGN, solar flares and, last but not least, gamma-ray afterglow from gamma-burst counterparts.
A Bismuth Germanate (BGO) 'veto' shield surrounds on five faces the detector planes of the IBIS instrument on-board the satellite INTEGRAL (INTErnational Gamma-Ray Astrophysics Laboratory). The Veto System provides anti-coincidence signals to the two imager layers covering the energy range from 20 keV to 10 MeV. The area to be shielded is about 8000 cm<SUP>2</SUP>, and with a shield thickness of 20 mm, this leads to a total BGO crystal weight of about 115 kg. This paper describes the shield design, and how some scientific and engineering requirements are implemented. Also results from tests with the Engineering Model are presented. Particular emphasis is given to the electronic signal chain, and its response to overload particles, mainly high energy protons, expected in the INTEGRAL orbit (Elliptic Earth Orbit with 72 h period). The overload response has been studied in detail both with a built-in Light Emitting Diode (LED) in the laboratory, and at a proton beam facility. Based on the lab measurements the expected blinding of the shield in-orbit is around 1%. This is obtained with a simple, but optimized chain, consisting of a front-end amplifier and a bi-polar shaper, that provides input to the trigger generator. Results from beam tests with proton energies from 60 to 300 MeV are reported, and it is demonstrated that the proton pulses in terms of amplitude, shape and duration are very similar to the simulated ones, and thus confirm the expected system response.
A proposal for an x-ray optics test facility based at a synchrotron radiation source is presented. The facility would incorporate a clean preparation area, and a large evacuable test area. The advantages of using a synchrotron as the source of the test radiation are discussed. These include the ability to produce a highly parallel beam of monochromatic x rays ranging from 200 eV to around 70 keV.
The MART-LIME is a large area x-ray experiment planned to be launched on board the Russian satellite Spectrum X-Gamma, as the high energy imager of a complement of broad band co- aligned x-ray telescopes. The energy range covered is 5 - 150 keV with an angular resolution of 8.6 arcminutes. The final detector configuration is now in its testing phase and includes the high pressure window comprising the 6 by 6 degree collimator, and the multiwire proportional counter (MWPC). The response to x-ray sources was investigated during the tests carried out at the Daresbury Laboratory (Warrington, UK) facilities The MWPC was filled up by a xenon-argon-isobutane gas mixture in order to evaluate the efficiency of the detector and in particular its linearity over the whole approximately 2,000 cm<SUP>2</SUP> sensitive area. At the same time the various parts of the apparatus have been simulated by using a Monte Carlo program. Results on the detector response and simulations are presented.
To follow up on the remarkable discoveries of the Compton Gamma Ray Observatory and GRANAT, the International Gamma Ray Astrophysics Laboratory (INTEGRAL) mission was selected by ESA as part of the agency's 'HORIZON 2000' strategic plan. It is scheduled to begin detailed gamma ray spectral and imaging studies, of unprecedented resolution, in the year 2001. One of the two main INTEGRAL instruments is a high performance imager. It features a coded aperture mask and a novel large area multilayer detector which utilizes both cadmium telluride and cesium iodide elements to deliver the fine angular-resolution approximately 12 arcmin, wide spectral response (15 keV to 10 MeV) and high resolution spectroscopy (6% at 100 keV) required to satisfy the mission's imaging objectives.
We have begun to study a mission to carry out the first high sensitivity imaging survey of the entire sky at hard x-ray energies (5 - 600 keV). The Energetic X-ray Imaging Survey Telescope (EXIST) would include 2 - 4 large area coded aperture telescopes with offset fields of view allowing total exposures of >= 500 ksec and flux sensitivities below 1 mCrab over the full sky in a year with time resolution from msec to months for each source as well as high spatial and spectral resolution for sources, transients and gamma-ray bursts. A pointed observatory phase, with the telescopes co-aligned, would follow and achieve still greater sensitivities and temporal coverage, allowing the detailed study of virtually all classes of accretion sources (cataclysmic variables to quasars) as well as diffuse galactic emission. The baseline concept originally proposed for the detector is a modularized array (4 X 4) of Cd-Zn-Te crystals (6.25 cm<SUP>2</SUP> each, or 100 cm<SUP>2</SUP>/module). An array of 5 X 5 modules, or 2500 cm<SUP>2</SUP> total detector area with 1.25 mm spatial resolution, would constitute the focal plane readout of each of the four telescopes. A brief descriptio of the proposed detector and telescopes and predicted backgrounds and sensitivity is given.
IAS, a CNR institute for space research in Astrophysics, in collaboration with IKI on their invitation, has developed, and is now under building, an X-Ray Imaging and Spectroscopic telescope as the high energy instrument on board the Observatory Spectrum X-Gamma. The scientific aim of this instrument, named MART-LIME, will be the detailed study of X-Ray sources emitting in the energy range 5 - 150 keV. The MART-LIME telescope is a follow up in a series of X-Ray detectors that have been developed, built at IAS and flown on board stratospheric balloons. It consists of a high pressure gas operated multiwire proportional counter with bidimensional spectral resolution coupled with a coded mask placed at 2.3 meter.
The International Gamma-Ray Astrophysics Laboratory (INTEGRAL) is a proposed joint ESA/NASA/Russia gamma-ray astronomy mission which will provide both imaging and spectroscopy. It is currently at the final stages of an ESA phase-A study which it is hoped will lead to it being adopted during 1993 as the second 'medium-class' mission within ESA's Horizon 2000 plan. Launched in less than 10 years time it will be the successor to the current generation of gamma-ray spacecraft, NASA's Compton Observatory (GRO) and the Soviet- French Granat/Sigma mission. The baseline is to have two main instruments covering the photon energy range 50 keV to 10 MeV, one concentrating on high-resolution spectroscopy, the other emphasizing imaging. In addition there will be two monitors--an X-ray monitor which will extend the photon energy range continuously covered down to a few keV, and an Optical Transient Camera which will search for optical emission from gamma-ray bursts.
Recent results obtained by balloon and satellite borne coded-mask instruments have been used to simulate the imaging performance of MART-LIME, a coded mask telescope to be flown on board the international observatory SPECTRUM-X-GAMMA on 1995. In particular, we discuss a 6x6 square degree field-of-view centered on the hard X-Ray source responsible for the high energy emission from Galactic Center, at energies above 30 keV. The contributions of GX1+4, GRS1758-25, Terzan 2, Tr 1741-322 and GX354-0 to this field-of-view are also considered. Deconvolved images obtained via the cross-correlation technique are presented. From these images, the limiting sensitivity of the telescope in a crowded sky field is correctly determined.
MART-LIME is a coded mask imaging telescope to be flown onboard the international observatory SPECTRUM X-(Gamma) in 1995. This high-energy instrument, the center of which is a high-pressure proportional counter sensitive to the 5 - 150 keV energy range, will be characterized by a limiting sensitivity of about 1 milliCrab for a 105 s observation period. The imaging capability of the instrument is provided by a coded-mask aperture system, used in conjunction with a position sensitive detector. The basic pattern of the coded aperture is a 71 X 73 URA mask (twin prime). With the addition of an outer frame comprising 18 pixels on each side, a fully coded field-of-view of 2.6 degree(s) X 2.6 degree(s) is obtained, while a partially coded field-of-view is achieved up to 6 degree(s). Test procedures used to determine the performance of the MART-LIME detector are discussed. Results showing the spectroscopic capabilities of a Laboratory-Prototype detector are presented.
The concept, operational principle, and test results are presented for a new type of high-pressure high-spatial resolution proportional counter with enhanced spectroscopic capability. The detector in its baseline configuration is to be filled with a xenon/quench gas mixture at 5 bar and is to be sensitive over the 5-150 eV energy range. The position resolution will range from 0.5 mm at the lower energies to around 1 mm at the upper end of the energy range. The very high timing resolution of this new detector allows high count rate capacity and enables the application of the escape gating technique to achieve a high spectral resolution at energies above the xenon K edge.
The capabilities of the European Photon Imaging Camera (EPIC), the main instrument of ESA's 'Cornerstone' mission in X-ray astronomy with multiple mirrors (XMM), are discussed. The CCD characteristics, spatial resolution, energy bandpass and faint source sensitivity, spectral resolution and sensitivity, and timing capability are addressed, and the scientific rationale of the EPIC is summarized. The EPIC instrument system concept is briefly described.
Consideration is given to a new type of position-sensitive MultiWire Proportional Counter proposed as the high-energy instrument for the Spectrum X-Gamma Satellite. Two of them are based on high-throughput X-ray optics, sensitive up to about 20 keV. The third one, MART-LIME, is the high-energy instrument to cover the band 5-150 keV. This X-ray observatory-class orbiter comprises three major coaligned instruments. The scientific objective of this hard X-ray telescope is to produce sky images with arcmin angular resolution and good spectral resolution and submilliCrab sensitivity, during a typical observation time of 100,000 sec. The MART-LIME experiment is expected to produce a breakthrough in high-energy astrophysics by means of deep observations over a wide field of view. The missions are to produce a complete hard X-ray catalog, which is still nonexistent at the milliCrab sensitivity level.