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.

MAXI, Monitor of All-sky X-ray Image, is an X-ray observatory on the Japanese Experimental Module (JEM) Exposed Facility (EF) on the International Space Station (ISS). MAXI is a slit scanning camera which consists of two kinds of X-ray detectors: one is a one-dimensional position-sensitive proportional counter with a total area of approximately 5000 cm², the Gas Slit Camera (GSC), and the other is an X-ray CCD array with a total area approximately 200 cm², the Solid-state Slit Camera (SSC). The GSC subtends a field of view with an angular dimension of 1 degree(s) times 180 degree(s) while the SSC subtends a field of view with an angular dimension of 1 degree(s) times a little less than 180 degree(s). In the course of one station orbit,MAXI can scan almost the entire sky with a precision of 1 degree(s) and with an X-ray energy range of 0.5- 30keV. We have developed an engineering model (EM) for all components of the SSC. Their performance test is ongoing. We have also developed several kinds of CCDs fabricated from different wafers. Since the thermal condition of the ISS is not suitable for the CCD operation, the operating temperature of the CCD estimated to be -85 approximately -50 degree(s) at the end of mission life. We therefore carefully need to choose CCD considering not only detection efficiency and readout noise but also the dark current. We report here the current status of the EM of the SSC and the X-ray responsibity of CCDs.

The essential optical components of the Swift X-ray Telescope (XRT) are already developed items. They are: the flight spare x-ray mirror from the JET-X/Spectrum-X program and a MOS CCD (CCD22) of the type currently operating in orbit as part of the EPIC focal plane camera on the XMM- Newton. The JET-X mirrors were first calibrated at the Max Plank Institute for Extraterrestrial Physics' (MPE) Panter facility, Garching, Germany in 1996. Half energy widths (HEW) of 16 arc seconds at 1.5 keV were confirmed for the two flight mirrors and the flight spare. The calibration of the flight spare was repeated at Panter in July 2000 in order to establish whether any changes had occurred during the four years that the mirror had been in storage at the OAB, Milan, Italy. This results reported in this paper, confirm that the resolution of the JET-X mirrors has remained stable over this storage period. In an extension of this test program, the flight spare EPIC camera was installed at the focus of the JET-X mirror to simulate the optical system of the Swift X-ray telescope. On-axis and off-axis point spread functions (PSFs) were measured and calibration data sets were used to obtain centroid positions of X-ray point sources. The results confirmed Swift's ability to determine the centroid positions of sources at 100mCrab brightness to better than 1 arc second and provided a calibration of the centroiding process as a function of source flux and off axis angle. The presence of background events in the image frame introduced errors in the centroiding process, making the choice of centroiding algorithm important. Algorithm performance and the trade-off between processing speed and centroiding accuracy were investigated.

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.

Based on the operational experience with the EPIC pn-CCD system on board of XMM-Newton, new imaging X-ray spectroscopic detector systems for future X-ray missions will be introduced in terms of energy, position and time resolving detectors. As the readout speed requirement in the case of single photon coating detectors increases drastically with the collecting area and improved angular resolution, but noise figures have to be on the lowest possible level, new detector schemes must be developed: Active pixel sensors (APS) for X-ray detection have the capability to randomly select areas of interest and to operate at noise levels below 1 electron (rms). About 1000 frames per second can be read out with a relatively low level of electric power with the proposed DEPFET arrays. One prominent candidate for the use of an APS is ESA's XEUS 0 the X-ray Evolving Universe Spectroscopy mission. It represents a potential follow-on mission to the cornerstone XMM-Newton, currently in orbit. The XEUS mission is considered as part of ESA's Horizon 2000⁺ program within the context of the International Space Station (ISS).

We present an experimental study of the performance of one-dimensional Distributed Read-Out Imaging Devices (DROIDs), based on two Ta/Al-based STJs placed on either side of a Ta absorber strip. We focus our discussion on the prospects of building large-format photon-counting imaging spectrometers for applications at soft X-ray energies. Tunnel-limited spectroscopical resolutions have already been demonstrated for optical photons. With a 20 x 100 micrometers ² absorber we have measured an intrinsic energy resolution of 2.1 eV FWHM for 500 eV photons. This demonstrates that at soft X-ray energies resolutions close to the tunnel limit are also feasible for these type of detectors. A detailed analysis of pulse-shapes with analytical models allows us to assess the main parameters that determine the performance of these detectors. In particular, we discuss the dependence of the quasiparticle diffusion constant on the temperature of the absorber. Extrapolation of these models indicates that it is possible to extend the length of the absorber to 1.5 mm, without a serious degradation of the detector's performance.

The pn-CCD camera on EPIC-XMM is the most advanced imaging X-ray spectrometer, as it combines high quantum efficiency, high speed readout and high energy resolution. The camera operates for almost two years as calibrated prior to launch. Future missions, like ESA's XEUS (X-ray Evolving Universe Spectroscopy) mission require higher spatial resolution, higher response at energies above 20 keV and most important a full frame readout rate increased by at least a factor of 20 for the first operational phase. XEUS represents a potential follow-on mission to the cornerstone XMM-Newton, currently in orbit. The XEUS mission is considered as part of ESA's Horizon 2000⁺ program within the context of the International Space Station (ISS.) In order to match the above requirements for the wide field imager of XEUS, we propose a frame store pn-CCD camera system based on the technology development of the EPIC (European Photon Imaging Camera) camera on XMM-Newton. Our goal is readout rate of 250 complete frames per second for 1024 x 1024 pixels with a pixel size of 75x75micrometers ², monolithically integrated on a 6 inch wafer. The concept and the new features of the frame store pn-CCD camera will be described. The focal plane layout, the readout concept and the expected scientific performance will be introduced. The implementation of thin aluminum filters, monolithically grown on the pn-CCD entrance window, will be discussed as well as the integration of a very fast spectroscopic detector being able to record 10⁶ counts per second with a FWHM of about 250 eV.

The polarisation of astrophysical source emissions in the energy range from a few tens of keV up to the MeV region is an almost unexplored field of high energy astrophysics. In order to improve the capabilities of performing polarimetric studies of hard X and soft gamma ray sources through Compton polarimetry, a CdTe based telescope (CIPHER: Coded Imager and Polarimeter for High Energy Radiation) is under study. This instrument is based on a thick (10 mm) CdTe position sensitive spectrometer made of four modules of 32x32 individual pixels, each with a surface area of 2x2 mm², corresponding to about 160 cm² active detection area. This detector, due to its intrinsic geometry, could allow efficient polarimetric measurements to be made between 100 keV and 1 MeV. In order to predict the polarimetric performance and to optimise the design and concept of the CIPHER detection plane, a Monte Carlo code based on GEANT4 library modules was developed to simulate the detector behaviour under a polarised photon flux. The Compton double event efficiency, as well bi-dimensional double event distribution maps and the corresponding polarimetric modulation factor will be presented and discussed. Modulation (Q) factors better than 0.30 and double event total efficiencies over 10 % for an energy range from 100 keV to 1 MeV have been obtained.

We report on the design and construction of a tiled Cadmium Zinc Telluride (CZT) detector array, suitable for use as an astronomical coded aperture imager. Four detector modules, each with 4 x 4 x 0.5 cm of CZT, readout by two 128 channel XA type ASICs, have been built and incorporated into a detector focal plane array. A passive shield/collimator surrounded by plastic scintillator encloses the detector on five sides and provides a 40 degree field of view. In this paper, we present our performance goals and some preliminary calibration results.

The recent technological developments and availability of mercuric iodide detectors have made their application for astronomy a realistic prospect. Mercuric iodide, because of its high resistivity and high density, can be used in a variety of astronomy instrumentation where high spectral resolution, low noise levels, stability of performance, resistance to damage by charged particles and overall ruggedness are of critical importance. X-ray detectors with areas of 12 to 100 mm square and 1 mm thickness have absorption efficiencies approaching 100% up to 60 keV. The spectral resolution of these detector's ranges from 400 eV to 600 eV at 5.9 keV, depending on their area, and the electronic noise threshold is less than 1.0 keV. Gamma ray detectors can be fabricated with dimensions of 25 mm x 25 mm x 3 mm. The spectral resolution of these detectors is less than 4% FWHM at energies of 662 keV. Because of the high atomic numbers of the constituent elements of the mercuric iodide, the full energy peak efficiency is higher than for any other available solid-state detector that makes measurements up to 10 MeV a possibility. The operation of gamma ray detectors has been evaluated over a temperature range of -20 through + 55 degrees Celsius, with only a very small shift in full energy peak observed over this temperature range. In combination with Cesium Iodide scintillators, mercuric iodide detectors with 25 mm diameter dimensions can be used as photodetectors to replace bulky and fragile photomultiplier tubes. The spectral resolution of these detectors is less than 7% FWHM at 662 keV and the quantum efficiency is larger than 80 % over the whole area of the detector.

The Keck Solar Two Gamma-Ray Observatory is a ground-based instrument is being developed to detect 20-300 GeV gamma rays by sampling the Cherenkov light generated as gamma rays and cosmic rays interact with the atmosphere. The observatory utilizes the Solar Two Pilot Power Plant in Barstow, California (Figure 1) which has the largest heliostat mirror area in the world. It has over 1,818 heliostats each with about 41 m² mirror area. The total active area is over 75,000 m². Thus, Keck Solar Two Gamma Ray Observatory has the potential to be the most sensitive ground-based gamma-ray detector between 20-300 GeV. The secondary mirror systems, each capable of viewing 32 heliostats has been designed. The secondary mirror systems also include the photomultiplier tube (PMT) camera, electronics, and heliostat field. The first secondary camera has been manufactured and it is being calibrated. Work on building the second secondary camera system with 32 heliostats has been started. When the second system is completed a 64 heliostat telescope will be ready to observe 50-300 GeV gamma rays. Further enlargement of the telescope to 128 or 256 heliostat is expected to lower the energy threshold to about 20 GeV.

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 spatial resolution of current MCP based detector devices (<10micrometers ) has reached the point when such phenomena as charge cloud asymmetry becomes important for the ultimate detector performance. We present a systematic study of the MCP charge cloud spatial distribution at the plane of the readout element. Our new readout - cross strip (XS) anode combined with a set of preamplifiers for each anode finger - allowed us to measure directly the distribution of electrons at the anode. The measurements of the charge cloud profile were done with a high accuracy owing to the extremely high spatial resolution of the XS anode - about 5 micrometers FWHM. The asymmetry of the charge cloud related to MCP channel bias was observed directly in these measurements. Our charge cloud propagation model was used to simulate the observed charge cloud asymmetry. Results of our calculations were compared with the experimental data, and a good agreement between those proves the validity of the model, which can be used for simulation of the charge cloud distribution in a wide range of detector operating parameters.

The techniques for manufacture of silicon (Si) MCP's at Nanosciences Corp have undergone significant changes over a relatively short period of time. This is expected in the developmental stages of any new technology, and we have attempted to track this progress by assessing the performance of successive generations of Si MCP's. The samples we have tested are 25mm format with approximately 7 micrometers pores, both with square and hexagonal pore shapes. We have measured the gain of single Si MCP's and the gain, pulse height, gain uniformity, background and quantum detection efficiency of Si MCP's in stacks. Hexagonal pore MCP's with high gain and open area ratios of >75% have been successfully fabricated. Gain of nearly 10⁴ for a single Si MCP has been achieved, and the quantum detection efficiency for Si MCP's has been shown to be the same as glass MCP's. The Si MCP background is as low as approximately 0.02 events sec ^-1 cm^-2 without shielding, giving significant improvement over even low noise glass MCP's. The image flat fields are free of any patterned modulation, and the gain uniformity is relatively good. Along with low stopping power for x, gamma and cosmic rays, stability to very high temperatures (>800 degree(s)C), and lack of reactivity with photocathodes, Si MCP's offer a new option in MCP applications.

We study the relation between diffusion and loss of charge produced in X-ray CCDs with the fitting method. We obtain the extent and the pulse height of each X-ray event in a CCD by a two-dimensional image-fitting the charge distribution of the event. For the monochromatic X-rays, we find that the event with small extent keeps all the charge produced, while that with larger extent than a certain value loses some part of the produced charge as a function of extent. The result suggests that the event with a small extent is produced by an X-ray absorbed in the depletion layer. On the other hand, the event with large extent corresponds to an X-ray absorbed in the field-free region. We develop two new methods which enable us to derive the relation between the extent of an event and the absorption depth. One is performed by illuminating well calibrated monochromatic X-ray source. The other is realized by using with two monochromatic X-rays and enables us to measure the thickness of the CCD depletion layer without calibrating absolute flux of the monochromatic X-rays.

We have developed a novel architecture to process 2-dimensional digital image data with very high speed. The architecture is realized with an FPGA to extract only the X-ray signals from the raw frame data of an X-ray CCD for an astronomical use. The circuit scale is small enough to be implemented in an FPGA currently available for a space use, while the data processing speed of 10⁷ pixels/sec is achieved. The architecture can be adapted in principle to a wide range of applications.

We are developing Monitor of All Sky X-ray Image (MAXI) which will be mounted on the Japanese Experiment Module of the International Space Station. MAXI is an all-sky X-ray monitor which scans the sky in every 90 minutes. The sensitivity will be as high as 7 mCrab (5 (sigma) level) in one scan and 1 mCrab in one-week accumulation. The GSC (Gas Slit Camera) instrument consists of twelve one-dimensional position sensitive proportional counters using the Xe++CO₂ gas and the carbon fiber anodes of 10micrometers diameter. The window size is 272 x 190 mm. The position is obtained by the charge division method. It is used to identify the source in the long rectangular field-of-view (1.5 x 80 degrees). Three cameras will be set to cover the 1.5 x 160 degrees arc. The position resolution is essentially important, which becomes better in the higher gas gain. We have tested gas mixtures of Xe+CO₂with CO₂ equals 0.2\%, 0.5\%, 1\%, 3%. The CO₂ equals 0.5\% showed the most uniform gas gain, but has a little after pulses. We chose the Xe (99%) + CO₂ (1%) combination for the flight counters. It can achieve the uniform gas gain in the cell and negligible after-pulse in high operating voltage. The engineering model of the counter (EM1) was build. We have tested the position resolution and the energy resolution across the counter. The position resolution and the energy resolution depend on the X-ray energy. On the basis of these results, together with the collimator response, we performed a realistic simulation.

The Italian Small Scientific Satellite AGILE is designed to operate in the energy range 30 MeV-50 GeV and will achieve an angular resolution of 5 to 20 for intense sources over a large field of view (better then 2 sr). The payload consists of a X-ray imaging detector (Super-Agile), a Silicon-Tungsten Tracker, a Cesium Iodide Mini-Calorimeter, an anticoincidence system, fast readout electronics and processing unit. The Mini-Calorimeter, comprises 2 orthogonal planes each consisting of 16 bars of CsI(Tl), it will contribute to the determination of the energy of the interacting gamma-rays and will allow the detection of Gamma Ray Bursts and other impulsive events from around 300 keV. A prototype of the Mini-Calorimeter has been tested both with laboratory sources and with charged particles (1 - 2 GeV/c) during some dedicated test campaign carried out in August 1999, in May 2000 and in November 2000 at the CERN T11 beamline (East Hall, CERN PS). The test set-up was completed with a prototype of the flight frontend electronic chain. A prototype of the digital data acquisition chain, which will be the basis of the payload Electronic Ground Support Equipment, has also been built and tested. The tests have been devoted to detector unit characterization and electronic characterization. The results of the tests carried out in 2000 are described and discussed.

INTEGRAL is the forthcoming European Space Agency's (ESA) satellite mission for gamma-ray astronomy, which will be launched in 2002. IBIS is the imaging telescope onboard INTEGRAL and will produce images of the gamma-ray sky in the region between 15 keV and 10 MeV by means of a two-layer position sensitive detection plane coupled with a coded aperture mask. The detection plane of IBIS comprises two detectors: ISGRI, operative in the 15 keV - 1 MeV range, and PICsIT, 150 keV - 10 MeV. The PICsIT instrument, which is the high energy plane of the IBIS imager, comprises 8 individual modules of 512 detection elements. The modules are arranged in a 4 x 2 pattern, while the pixels are in a 16 x 32 array within each module. Detailed simulation programs of PICsIT qualification and flight model have been set up in order to provide a complete scientific characterization of the detector in terms of spectral and imaging performances. These simulation programs have also been used to reproduce the on-ground calibration results, and will be the basis for the production of the response matrix.

We present results from the flight of two prototype CZT detectors on a scientific balloon payload in September 2000. The first detector, referred to as CZT1, consisted of a 10 mm x 10 mm x 2 mm CZT crystal with a single gold planar electrode readout. This detector was shielded by a combination of a passive collimator in the front, giving a 40 degree field of view and surrounded by plastic scintillator, and a thick BGO crystal in the rear. The second detector, CZT2, comprised two 10 mm x 10 mm x 5 mm CZT crystals, one made of eV Products high pressure Bridgman material and the other of IMARAD horizontal Bridgman material, each fashioned with a 4 x 4 array of gold pixels on a 2.5 mm pitch. The pixellated detectors were flip-chip-mounted side by side and read out by a 32-channel ASIC. This detector was also shielded by a passive/plastic collimator in the front, but used only additional passive/plastic shielding in the rear. Both experiments were flown from Ft. Sumner, NM on September 19, 2000 on a 24 hour balloon flight. Both instruments performed well. CZT1 recorded a non-vetoed background level at 100 keV of approximately 1 x 10^-3 cm^-2s^-1keV^-1. Raising the BGO threshold from 50 keV to approximately 1 MeV produced only an 18% increase in this level. CZT2 recorded a background at 100 keV of approximately 4 times 10^-3 cts cm^-2s^-1keV^-1 in the eV Products detector and approximately 6 x 10^-3 cts cm^-2s^-1keV^-1 in the IMARAD detector, a difference possibly due to our internal background subtracting procedure. Both CZT1 and CZT2 spectra were in basic agreement with Monte Carlo simulations, though both recorded systematically higher count rates at high energy than predicted. No lines were observed, indicating that neutron capture reactions, at least those producing decay lines at a few 100 keV, are not significant components of the CZT background. Comparison of the CZT1 and CZT2 spectra indicates that passive/plastic shielding may provide adequately low background levels for many applications.

A breadboard setup constructed at MOXTEK, Inc., is capable of capturing both x-ray diffraction (XRD) and x-ray fluorescence (XRF) information simultaneously using a charge-coupled device (CCD) as the x-ray detector. This preliminary setup will lead to a prototype simultaneous XRD/XRF instrument. NASA is funding the project because it could be used for future Mars missions for analysis of rocks. The instrument uses a CCD to capture both the energy and the position of an incoming x-ray. This is possible because each pixel acts as a spatially addressable energy- dispersive detector. A powdered sample of material is placed in front of the CCD, which in turn is bombarded by a collimated x-ray beam. The instrument's critical features, the x-ray source, collimation optics and x-ray transparent windows need to be optimized in the size and power to allow the instrument to be portable. In this paper the instrument's design parameters as well as the properties of both the CCD as x-ray detector and the low-power consumption tube are investigated.