The Chandra X-Ray Observatory, the x-ray component of NASA's Great Observatories, was launched early in the morning of 1999, July 23 by the Space Shuttle Columbia. The Shuttle launch was only the first step in placing the observatory in orbit. After release from the cargo bay, the Inertial Upper Stage performed two firings, and separated from the observatory as planned. Finally, after five firings of Chandra's own Integral Propulsion System--the last of which took place 15 days after launch--the observatory was placed in its highly elliptical orbit of approximately 140,000 km apogee and approximately 10,000 km perigee. After activation, the first x-rays focused by the telescope were observed on 1999, August 12. Beginning with these initial observations one could see that the telescope had survived the launch environment and was operating as expected. The month following the opening of the sun-shade door was spent adjusting the focus for each set of instrument configurations, determining the optical axis, calibrating the star camera, establishing the relative response functions, determining energy scales, and taking a series of `publicity' images. Each observation proved to be far more revealing than was expected. Finally, and despite an initial surprise and setback due to the discovery that the Chandra x-ray telescope was far more efficient for concentrating low-energy protons that had been anticipated, the observatory is performing well and is returning superb scientific data. Together with other space observations, most notably the recently activated XMM-Newton, it is clear that we are entering a new era of discovery in high-energy astrophysics.

We present here results of the on-orbit calibration of the point spread function (PSF), comparing it with our predictions. We discuss how the PSF varies with source location in the telescope field of view, as well as with the spectral energy distribution of the source.

The Chandra X-ray Observatory was launched in July 1999, and is returning exquisite sub-arc second X-ray images of star groups, supernova remnants, galaxies, quasars, and clusters of galaxies. In addition to being the premier X-ray observatory in terms of angular and spectral resolution, Chandra is the best calibrated X-ray facility ever flown. We discuss here the calibration of the on-axis effective area of the High Resolution Mirror Assembly. Because we do not know the absolute X-ray flux density of any celestial source, this must be based primarily on ground measurements and on modeling. We use celestial sources which may be assumed to have smoothly varying spectra, such as the BL Lac object Markarian 421, to verify the continuity of the area calibration as a function of energy across the Ir M-edges. We believe the accuracy of the HRMA area calibration is of order 2%.

Prior to launch, the High Resolution Mirror Assembly (HRMA) of the Chandra X-ray Observatory underwent extensive ground testing at the X-ray Calibration Facility (XRCF) at the Marshall Space Flight Center in Huntsville, Alabama. The resulting data were used to validate a high fidelity raytrace model for the HRMA performance. Further observations made during the post-launch Orbital Activation and Calibration period allow the on-orbit condition of the X-ray optics to be assessed. Based on these ground-based and on-orbit data, we examine the alignment of the X-ray optics based on the off-axis point spread function. We discuss how single-reflection ghost data obtained at XRCF can be used to better constrain the HRMA optical axis data. We examine the vignetting and the single-reflection ghost suppression properties of the telescope. Slight imperfections in alignment lead to a small azimuthal dependence of the off- axis effective area; the morphology of off-axis images also shows an additional small azimuthal dependence varying as 1/2 the position angle.

We have performed a series of measurements with the Physikalisch-Technische Bundesanstalt beamline of the electron storage ring BESSY 1 which provide the basis for the absolute calibration of the Advanced CCD Imaging Spectrometer (ACIS). ACIS is a prime focal plane instrument aboard the recently-launched Chandra X-ray Observatory. We have achieved an absolute detection efficiency knowledge accurate to better than 5% over the 0.3 - 4 keV band. We describe our measurement and analysis techniques, including our detector response modeling and pileup corrections. We summarize a variety of external and internal consistency checks which provide the basis for our error estimates. We discuss the factors limiting the accuracy of our measurements.

The High Resolution Camera (HRC) is one of the two focal plane instruments on NASA's Chandra X-ray Observatory which was successfully launched July 23, 1999. The Chandra Observatory will perform high resolution spectroscopy and imaging in the X-ray band of 0.1 to 10 keV. The HRC instrument consists of two detectors, the HRC-I for imaging and the HRC-S for spectroscopy. In this paper we present an overview of the in-flight performance of the High Resolution Camera and discuss some of the initial scientific results.

The Chandra spacecraft has been launched successfully on July 23, 1999. The payload consists of a high resolution X- ray telescope, two imaging detector systems in the focal plane and two transmission gratings. Each one of the two gratings can be put in the beam behind the telescope and the grating spectrometers are optimized for high and low energy, respectively. The Low Energy Transmission Grating Spectrometer consists of three parts: the high-resolution telescope, the transmission grating array and the detector, to read-out the spectral image.

We present preliminary results from observations of supernova remnants by the Chandra X-ray Observatory. The data include imaging spectroscopy from objects observed with both GTO and GO data. The high spatial resolution of Chandra is revealing a wealth of small-scale structure in these remnants. Specifically, we have resolved the remnant of SN1987A, and have discovered fine-scale structure in N103B and G292.0+1.8.

The ESA X-ray Multi Mirror mission, XMM-Newton, carries two identical Reflection Grating Spectrometers behind two of its three nested sets of Wolter I type mirrors. The instrument allows high-resolution (E/(Delta) E equals 100 to 500) measurements in the soft X-ray range (6 to 38 A or 2.1 to 0.3 keV) with a maximum effective area of about 150 cm² at 15 A. The satellite was successfully launched on December 10, 1999, from Guyana Space Center. Following the launch the instrument commissioning was started early in 2000. First results for the Reflection Grating Spectrometers are presented concentrating on instrumental parameters such as resolution, instrument background and CCD performance. The instrument performance is illustrated by first results from HR 1099, a non-eclipsing RS CVn binary.

The high throughput X-ray spectroscopy mission XMM is the second `Cornerstone' project in the ESA long term Program for Space Science. This observatory has at its heart three heavily nested Wolter I grazing incidence X-ray telescope. The telescopes are equipped with non-dispersive spectroscopic imaging instruments (EPIC, European Photon Imaging Camera) and medium resolution dispersive spectroscopic instruments (RGS, Reflection Grating Spectrometer). Because of the sensitivity of the XMM instruments X-ray detectors in the visible wavelength range, a high suppression of the visible radiation emitted from out-of-field sources (earth, sun) must be ensured. The straylight reduction capability is quantified by the PST (Point Source Transmittance). The experimental verification of the PST on the XMM flight model mirror modules for off- axis angles between 1 degree(s) and 85 degree(s) is presented in this paper. For the first time a straylight test of a complete telescope was performed in air measuring the telescope PST over a range of 9 orders of magnitude (10^-2 to 10^-11).

Soft X-ray response of X-ray Imaging Spectrometers (XIS) for the Astro-E satellite is measured with a grating spectrometer system at Osaka. First, relation between incident X-ray energy and output pulse height peak (E-PH relation) is examined with an SX grating. It is found that jump in the E-PH relation around Si-K edge is at most 2.7 eV. Second, quantum efficiency (QE) of the XIS in 0.4 - 2.2 keV range is measured relatively to the reference CCD of which absolute QE was calibrated with a gas proportional counter. The QE is fitted with a model in which CCD gate structures are considered. Systematic error on the QE results is estimated by referring an independent measurement. Third, tuning and improvement of the response function is performed. We employ six components to reproduce the response profile of the XIS. In this paper, improvement of one component which is originated in the events absorbed in the channel-stop is presented. Nevertheless, Astro-E was lost due to the launch failure. We overview the XIS project in its flight model phase, modified points of the design, problems and solutions etc., in order to be utilized in a possible recovery of the satellite.

We present the detailed study of the response function of X- ray CCD cameras (XIS; X-ray Imaging Spectrometer). A pulse height distribution for monochromatic X-rays show a low- energy tail component and several weak lines in addition to main peak corresponding to incident X-ray energy. We divided the response function into six components; main peak, sub peak, triangle component, constant component, Si escape, and Si line. Each of them represents different physical processes in the CCD. We did the data fitting, numerical calculations, and Monte Carlo simulations to study energy dependence of the shape and intensity of these components, and made the response function as a function of X-ray energy.

We report on the development of an imaging detector with high energy resolution for the X-ray Evolving Universe Spectroscopy Mission (XEUS). The type of detector we are studying is a voltage biased superconducting transition edge microcalorimeter, operated at sub-Kelvin temperatures. Baseline for the imaging function is an array of these calorimeters, read out using SQUID amplifiers. Based on the performance of and experience with single-pixel micro calorimeters, we discuss new design concepts and read-out of imaging arrays of micro calorimeters. Critical design elements are the thermal transport from the pixels to the bath, operating temperature and cross talk. The requirements of a SQUID read-out system for the XEUS spectrometer are addressed and the areas where development is needed are identified.

The Wide-field X-ray Monitor is one of the scientific instruments carried on the High Energy Transient Explorer 2 (HETE-2) satellite planned to be launched in May, 2000 (on the present schedule in February, 2000). HETE-2 is an international mission of a small satellite dedicated to provide broad band observations and accurate localizations of gamma-ray bursts (GRBs). The first HETE satellite was lost due to a Pegasus XL rocket mishap on November 4, 1996. The HETE-2 has been developed on basically the same concept except that the UV cameras were replaced with the Soft X-ray Camera. A unique feature of this mission is its capability of determination and transmission of GRB coordinates in near real time through a network of primary and secondary ground stations.

Monitor of All-sky X-ray Image (MAXI) is the first astrophysical payload which will be mounted on the Japanese Experiment Module Exposed Facility of International Space Station in 2004. It is designed for monitoring all-sky in the x-ray band by scanning with slat collimators and slit apertures. Its angular resolution and scanning period are approximately 1 arc degree and 90 minutes, respectively. MAXI employs two types of X-ray camera. One is Gas slit Camera (GSC), the detectors of which are 1D position sensitive proportional counters. Its position resolution is approximately 1.0 mm along carbon anode wires. GSC covers the 2.0 - 30 keV energy band. We have found an interesting feature in the energy response: monochromatic X-rays are detected with a peculiar hard tail in the spectra. The physical mechanism causing the hard tail is still unclear. The other camera is Solid-state Slit Camera (SSC). We employ a pair of SSCs, each of which consists of sixteen CCD chips. Each CCD has 1024 X 1024 pixels, and each pixel is 24 X 24 micrometers. The CCDs are to be operated at -60 degree using Peltier coolers. SSC covers an energy range of 0.5 - 10.0 keV. The test counters and test chips are evaluated in NASDA, Riken, and Osaka-University. The continuous Ethernet down link will enable us to alert the astronomers in all over the world to the appearance of X-ray transients, novae, bursts, flares etc. In this paper we will report on the current status of the MAXI mission.

We have developed an engineering model of CCD chips and the analogue electronics for the Solid-state Slit Camera. To optimize its X-ray responsibility, we have also developed a flexible general-purpose CCD data acquisition system. We tested many kinds of clock patterns with different voltage levels. We report here our new CCD system and preliminary results of optimization of clock voltages.

We present the latest design concepts of CCDs for the next generation of X-ray astronomical applications together with test results of new detector developments for these applications. In particular we consider ways of overcoming the fundamental limitations of these detectors, namely area coverage and low readout speeds. The manufacture of a high yielding, highly efficient CCD with a well understood response at all energies remains a high priority and we discuss our program to achieve this goal. Amongst other features: increased deep depletion and state of the art noise performance will be examined.

Large format arrays covering a wide bandwidth from 1 eV to 25 keV will be used in the focal plane of X-ray telescopes as well as in adaptive optics systems. As the readout speed requirements increase drastically with the collecting area, but noise figures have to be on the lowest possible level, CCD-type detectors do not seem to be able to fulfill the experiment expectations. Active pixel sensors (APS) have the capability to randomly select areas of interest and to operate at noise levels below 1 electron (rms). One prominent candidate for the use of an APS is XEUS: The X-ray Evolving Universe Spectroscopy mission. It represents a potential follow-on mission to the ESA cornerstone XMM currently in orbit. The XEUS mission was considered as part of ESA's Horizon 2000⁺ within the context of the International Space Station.

A novel type of micro-pore optics for the X-ray regime has been developed. These optics have a radial design instead of the square packing in the more traditional Lobster-eye optics. With such a design true imaging, without a crucifix in the focus, can be achieved. We demonstrate that the walls inside the square pores are good enough to produce sub- arcminute focussing up to photon energies above 10 keV. The current performance of the optics is limited by large-scale distortions of the plates, probably caused by the method to fuse the fibers together.

We discuss the observational requirements for future x-ray planetary and astrophysics missions and present preliminary laboratory results from our compound semiconductor program. The detectors used in the tests were simple monolithic devices, which are used in conjunction with a detailed material science and technology developmental program intended to produce near Fano limited, pixilated hard X-ray detectors. In practical terms, this means producing active arrays, comprised of over 10³ pixels each being of order 100 microns in size, with spectral resolving powers, E/(Delta) E > 20 at 10 keV and high quantum efficiencies over the energy range 1 to 200 keV. Four materials are currently under study--GaAs, HgI₂, TlBr and CdZnTe. In the cases of GaAs and CdZnTe, the detector energy resolution functions are approaching the Fano limit.

We present an experimental study of the performance of Distributed Read-Out Imaging Devices (DROIDs), 1- and 2-D photon-counting imaging spectrometers, based on Ta/Al-based STJs placed on a Ta absorber. Results obtained with highly collimated illumination with 10 keV X-ray photons clearly demonstrate the imaging capabilities of 2-D DROIDs. The derived spatial FWHM resolution is 7 micrometers for a 200 X 200 micrometers ² absorber. With a 1-D DROID we have measured an intrinsic energy resolution of 15 eV FWHM for 6 keV photons. At high energies (E > 6 keV) the resolution is limited by spatial fluctuations in the qp recombination rate.

For future x-ray satellite missions and other applications we propose a novel sensor which is based on the `DEPleted Field Effect Transistor (DEPFET)'. MOS-type DEPFETs (DEPMOS) are employed in prototype designs of pixel detectors ready for production. The device operated on a fully depleted silicon wafer allows an internal charge amplification directly above the position where the signal conversion takes place. A very low gate capacitance of the DEPMOS transistor leads to low noise amplification. In contrast to CCDs neither transfer loss nor `out of time events' can occur in a DEPFET-array. Fast imaging and low power consumption can be achieved by a row by row selection mode. The signal charge stored in a potential minimum below the transistor channel can be read out non destructively and repeatedly. By shifting the charge between two neighboring DEPMOS amplifiers the repeated signal readout leads to significant noise reduction. Concept, design and device simulations are presented and consequences of the expected properties for applications in x-ray imaging are discussed.

Ultra-high resolution imaging in the x-ray has the potential to revolutionize the way astronomers view the heavens. Through the use of interferometry at grazing incidence we can image the x-ray sky at the milli-arcsecond (or better) level. In this paper we describe the baseline design of the Maxim Pathfinder Mission, which will be the first interferometric x-ray observatory whose goal is to image the sky at 100 micro-arcsecond resolution in the 0.5 - 1.5 keV band with about 100 cm² of collecting area. This resolution is adequate to image the coronae of nearby stars and the accretion disks of quasars.

A prototype grazing incidence interferometer has been built and tested at EUV and X-ray wavelengths using a 120 meter long vacuum test facility at Marshall Space Flight Center. We describe the design and construction of the interferometer, the EUV and x-ray sources and detector systems, and compare the interferometric fringe measurements with theoretical predictions.

Sensitive nuclear line spectroscopy for observations of prompt emission from supernovae, as well as mapping of remnants has been a primary goal of gamma-ray astrophysics since its inception. A number of key lines lie in the energy band from 10 - 600 keV. In this region of the spectrum, observations have to-date been limited by high background and poor angular resolution. In this paper, we present several designs capable of extending the sensitivity of grazing incidence optics into this energy range. In particular, we discuss a 15 m focal length design for NASA's High-Sensitivity Spectroscopic Imaging Mission concept, as well as a 50 m focal length design which can extend ESA's XEUS mission into this band. We demonstrate that an unprecedented line sensitivity of 10^-7 cm^-2s^-1 can be achieved for the most important lines in this energy band.

In this paper we will report on recent progresses obtained in producing astronomical X-ray optics based on multilayer coatings exploiting the replication technique by Ni electroforming of the mirror support shell. It is well known that the use of multilayer reflectors with appropriate structures to be utilized instead of usual high density material (Ni, Au or Ir) monolayer mirrors can allow the extension of focusing techniques also in the hard X-ray energy band (10 - 100 keV). In addition, multilayer mirrors can offer important advantages also for applications in the classical X-ray band (0.1 - 10 keV), e.g., the enhancement of the effective area of a given telescope in a particular energy region of spectroscopical interest. The replication technique by Ni electroforming has already been successfully exploited for making the soft X-ray optics with Au coatings of the Beppo-SAX, JET-X and XMM-Newton space experiments. These telescopes are not only characterized by a large throughput, but they have also shown very good imaging capabilities. The approach under investigation from our group for the realization of multilayer grazing incidence telescopes in directly derived, with appropriate modifications, from that experience. We have already been able to fabricate by Ni electroforming replication flat Ni/C multilayer mirrors with a very good X-ray reflectivity. Here we will present some results obtained from the optical and X-ray characterization of conical and double-conical prototype optics recently realized from our group following the same technique. The obtained results are very promising.

High sensitivity hard X-ray data by means of focusing optics is crucially important to investigate active galaxies and cluster of galaxies. We have developed focusing telescopes with platinum-carbon multilayer coatings. The energy band is broadened by multilayers with graded periodic length, so called `Supermirrors'. We were successful to obtain hard X- ray images in the energy band from 25 to 40 keV with a demonstration model of telescope with 20 mirror shells of supermirrors. The flight model of supermirror telescope is now in production for balloon flight in the summer of 2000. The current status of the balloon mission and future application of supermirror technology is discussed.

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.

The Constellation X-ray Mission is the next major x-ray- astronomy mission in the NASA Space Science road map. As a follow-on to the Chandra X-ray Observatory--nee, the Advanced X-ray Astrophysics Facility--Constellation X will provide high-throughput, high-resolution spectroscopy to probe the gravitational field, kinematics, temperature, density, composition and ionization state of cosmic sources. The Constellation-X observatory system comprises four separate satellites, each with one large Spectroscopy X-ray Telescope (SXT, with a pixelated microcalorimeter and a reflection-grating-CCD spectrometer) and three smaller Hard X-ray Telescopes (HXTs, with pixelated hard-x-ray detectors). Essential to the success of Constellation X is the development of large (1.6-m-diameter), lightweight optics for the SXT mirror assembly. With the Smithsonian Astrophysical Observatory, teams led by NASA's Marshall Space Flight Center, by NASA's Goddard Space Flight Center, and by Italy's Osservatorio Astronomico di Brera are currently developing competing mirror techniques for lightweight SXT optics, toward achieving the required system-level half-power diameter--better than 15 arcsec.

The classical Wolter Type 1 X-ray telescope consists of two grazing incidence mirrors, a confocal paraboloid and hyperboloid. This design exhibits perfect geometric imaging on-axis (i.e., no spherical aberration) but suffers from severe field curvature, coma, astigmatism, and higher-order aberrations such as oblique spherical aberration. The Wolter-Schwarzschild design, consisting of two general aspheric grazing incidence surfaces, is corrected for both spherical aberration and coma, thus yielding very good geometrical performance at small field angles that becomes severely degraded at large field angles. The image quality criterion for stellar (small-field) X-ray telescopes is frequently expressed in terms of an on-axis fractional encircled energy, with the off-axis performance being dictated by the field-dependent aberrations characteristic of the design. A more appropriate image quality criterion for wide-angle applications is some area-weighted-average measure of resolution that maximizes the number of spatial resolution elements over a given operational field-of-view (OFOV). In practice, scattering effects from residual optical fabrication errors and detector effects (finite pixel size and charge spreading) dominate geometrical aberrations for small field angles whereas the geometrical aberrations dominate the image degradation at large field angles. Under these conditions, there is little merit in a telescope design corrected for coma (or even spherical aberration). Our new image quality criterion has led us to a whole new class of generalized Wolter Type I (hyperboloid- hyperboloid) designs that can be optimized for a given OFOV. A specific design and its predicted systems performance for the Solar X-ray Imager mission are described in detail.

A better random method used for improving light throughput of a soft X-ray multilayer has been developed in the 18 - 20 nm spectral region, it bases on the traditional theory of periodic multilayer, a 8% gain in integrated reflectance is obtained. We present ensemble calculation at the same time, and the multilayer is fabricated by magnetron sputtering. Finally low-angle X-ray diffraction and reflectance comparative measurement are used for testing the multilayer. The results demonstrate that layer thickness disorder yields band broadening (for both wavelength and angle) and increased integrated reflectance in the spectral range with respect to periodic multilayer, but accompanied with a reduction in reflectance peak. Layer thickness disorder makes it more difficult to fabricate broadband multilayer, raising the techniques of control layer thickness is the keystone of experiments.

Discussions of optimizing wide-field x-ray optics, with field-of-view less-than 1.1 degree-squared, have been made previously in the literature. However, very little has been published about the optimization of wide-field x-ray optics with larger field-of-views, which technology could greatly enhanced x-ray surveys. We have been working on the design of a wide-field (3.1 degree-squared field-of-view), short focal length (190.5 cm), grazing incidence mirror shell set, with a desired rms image spot size of 15 arcsec. The baseline design consists of Wolter 1 type mirror shells with polynomial perturbations applied to the baseline design. The overall optimization technique is to efficiently optimize the polynomial coefficients that directly influence the angular resolution, without stepping through the entire multi-dimensional coefficient space. We have investigated optimization techniques such as the downhill simplex method, fractional factorial, and response surface (including Box- Behnken and central composite) design. We have also investigated the use of neural networks, such as backpropagation, general regression, and group method of data handling neural networks. We report our findings to date.

We describe recent progress toward producing a segmented mirror that meets the mass and angular resolution requirements for the Constellation-X Spectroscopy X-ray Telescope (SXT). While the segmented approach has its heritage in conical thin foil X-ray mirrors pioneered at GSFC, the Constellation-X implementation introduces innovations in nearly all components. The baseline configuration uses thermally formed glass for reflector substrates; thermally formed Be is being investigated as an option. Alignment is performed using etched Si microstructures that locate reflectors to submicron accuracy. The only aspect preserved from previous mirrors is epoxy replication of the X-ray reflecting surface. Thus far, all developments have been at the component level. Nonetheless, we have made substantial progress toward meeting the Constellation-X SXT angular resolution goal.

We describe our design for a mini-Schmidt all-sky monitor. By using standard micro-machining techniques we are able to build a module that is smaller, lighter and has a greater open area than previous prototypes. In addition, we retain the benefit of high quality metal-coated flat glass reflecting surfaces.

A thin crystal with a thickness of approximately micrometers makes it possible to disperse incident x rays in a certain energy band, like a grating. We report a current performance of this new spectroscopic device. We show that Ti K (alpha) ₁ and K (alpha) ₂ lines are simultaneously diffracted to different directions making a two peaks. The experiment shows the energy resolving power of (E/(Delta) E > 3000) over approximately 24 eV range. A brief comparison will be presented among this thin crystal, gratings and Bragg crystals.

We have developed a completely new type of general-purpose CCD data acquisition system which enables us to drive any kinds of CCD with any kinds of clocking modes. A CCD driver system widely used before is consisted of analog multiplexer (MPX), digital-to-analog converter (DAC), and operational amplifier. DAC is used to determine high and low voltage levels and MPX selects each voltage level using TTL clock. In this kind of driver board, it is difficult to reduce the noise caused by a short of high and low level in MPX and to select many kinds of different voltage levels.

The energy resolution degradation of the ACIS CCDs on board the Chandra X-ray Observatory has been under investigation since the effect was first recognized two months after launch. A series of laboratory CCD irradiations with electrons and protons have taken place, leading to the belief that low energy protons are responsible for the damage. In order to confirm this, an experiment has been devised to represent the flight experience of the ACIS CCDs, and the results to date are shown here.

We measure the polarization degree of monochromatic X-rays from an electron impact type X-ray generator through a double crystal spectrometer. The double crystal spectrometer is installed so that it enhances the polarization from the generator by its different efficiency for (pi) and (sigma) polarized X-rays. Measurement is performed for applied high voltage (HV) of 20 kV to 50 kV, and monochromatic X-ray energy in the unit of keV (Ex) of 0.7 to 0.9 times HV. We obtain the polarization degree of 0.48 and 0.41 for HV equals 20 and HV equals 50 with Ex/HV equals 0.9. We also measure the polarization degree of direct beam without the monochrometer, comparing the polarization boosting factor by crystals measured with theoretical model. The system is good for getting moderate intensity of partially polarized monochromatic X-ray beam.

The replication technology represents an important alternative to other methods of X-ray optics production. We report on the past (first replicated X-ray mirror has been produced by our group just 30 years ago), present and future of replication of X-ray optics with emphasis on grazing incidence optics of various types and geometry. The various types of X-ray optics produced by replication with emphasis on astronomical optics are described and summarized. It is shown that the replicated X-ray optics will still play a major role in future space experiments and projects such as the ESA XEUS project and other coming missions.

The recent imaging X-ray telescopes have quite limited field of view of order of 1 degree or so. The development of wide- field X-ray telescopes with large field of view, reasonable angular resolution and high sensitivity can play an important role in future of X-ray astronomy and astrophysics. An important alternative is the Lobster eye X- ray optics theoretically described in the past but not yet constructed and used in a real experiment. We review the wide-field X-ray optics arrangements and discuss their preferences and drawbacks. We report on the design, development, manufacture and tests of first test X-ray objectives based on both Angel and Schmidt lobster eye geometry. We also suggest strategy for further developments in this area and discuss the scientific importance of space experiments based on lobster eye optics.

We discuss the development of X-ray multilayer coatings for use as broad-band reflectors operating at energies above 100 keV. Such coatings can be used to produce hard X-ray telescopes that will make possible a variety of entirely new astronomical observations. We summarize our recent investigation into the growth, structure and hard X-ray performance of depth-graded W/Si multilayers, present follow-up information on Cu/Si multilayers, and discuss preliminary results obtained with Ni/Si, Ni_.8Cr_.2/Si, and Ni_.93V_.07/Si multilayers.

The GoldHelox Solar X-ray Telescope underwent several tests during the years of 1997 - 1999, and continues through the testing phase of the project. The instrument itself, a solar telescope to ride on board the Space Shuttle, is designed to photograph the sun in soft x-ray wavelengths between 171 angstroms to 181 angstroms. Critical to its success, many tests are required to insure safety, robustness, and overall accuracy of the telescope during its mission. Among these are shake table tests, optical tests, vacuum integrity, and thermal analysis. This paper describes the GoldHelox project including its current status as a mission, the tests performed on the instrument to date, and the tests pending.

Grazing incidence mirror parameters and constraints for x- ray interferometry are described. We present interferometer system tolerances used to define mirror surface accuracy requirements. Mirror material, surface figure, roughness, and geometry are evaluated based on analysis results. We also discuss mirror mount design constraints, finite element analysis, environmental issues, and solutions. Challenges associated with quantifying high accuracy mirror surface quality are addressed.

In this paper we present and compare flight results with the latest results of the ground calibration for the HRC-I detector. In particular we will compare ground and in flight data on detector background, effective area, quantum efficiency and point spread response function.

The High Resolution Camera (HRC) is one of two focal plane instruments on the NASA Chandra X-ray Observatory which was successfully launched on July 23, 1999. The Chandra X-ray Observatory was designed to perform high resolution spectroscopy and imaging in the X-ray band of 0.07 to 10 keV. The HRC instrument consists of two detectors, HRC-I for imaging and HRC-S for spectroscopy. Each HRC detector consists of a thin aluminized polyimide blocking filter, a chevron pair of microchannel plates and a crossed grid charge readout. The HRC-I is an approximately 100 X 100 mm detector optimized for high resolution imaging and timing, the HRC-S is an approximately 20 X 300 detector optimized to function as the readout for the Low Energy Transmission Grating. In this paper we discuss the in-flight performance of the HRC-S, and present preliminary analysis of flight calibration data and compare it with the results of the ground calibration and pre-flight predictions. In particular we will compare ground data and in-flight data on detector background, quantum efficiency, spatial resolution, pulse height resolution, and point spread response function.

HESSI will image Solar flares with spatial resolution ranging from 2 and 190 arcsec over the energy range from 3 keV to approximately equals 100 keV and as low as 35 arcsec for energies up to 20 MeV, respectively. The system is based on Fourier- transform imaging in connection with high-resolution Ge- detectors. In order to achieve arcsec-quality images with an instrument having only arcmin alignment requirements one needs in addition two precise aspect systems: (1) The Solar Aspect System (SAS) will provide Sun aspect data with high precision (< 0.2 arcsec relative and 1 arcsec absolute) and at high frequency (100 Hz). It consists of three identical lens/filter assemblies with focus Sun images on three 2048 X (13 micrometers )² linear CCDS at 1.55 m focal distance. Simultaneous exposures of three chords of the focused solar images are made and the pixels spanning each solar limb are recorded. (2) The Roll Angle System (RAS) will provide precise (arcmin) information on the roll angle of the rotating spacecraft. The RAS is a star scanner which points out radially and observes stars at 75 degrees from the Sun direction using a commercial lens and a fast CCD. The passage of a star image over the CCD will induce a signal in one or several pixels and the timing of this signal defines the roll angle, once the star has been identified by comparing its pixel position and amplitude with a star map. With a limiting magnitude of mv equals 3 we expect to observe at least 1 star per revolution (during direct Sun view) over 1 year; on the average we will detect about 10 stars/revolution. We report on the design, construction and calibration measurements of the SAS and RAS flight-model instruments.

The primary object of HESSI is to study the explosive energy release in solar flares. HESSI will image flares with spatial resolution ranging between 2 and 35 arcseconds over the energy range 3 keV to 20 MeV. The system is based on Fourier-transform imaging in connection with high-resolution Ge-detectors. HESSI uses 9 Rotating Modulation Collimators, each consisting of a pair of widely separated (1.55 m) grids mounted on the rotating spacecraft. The grid pitches range from 34 micron to 2.75 mm in steps of sqrt(3). This gives angular resolutions that are spaced logarithmically from 2.3 arcseconds to 3 arcmin, allowing sources to be imaged over a wide range of angular scales. In our design the most critical performance parameter, the relative twist between the two grids of each pair--can be very precisely monitored on ground (on a level of several arcseconds) by a special Twist Monitoring System (TMS). Extensive measurements and cross-calibrations between the TMS and several coordinate measuring machines before and after the environmental tests demonstrated the precision and stability of the alignment to be on the order of 5 arcseconds.

At the Osservatorio Astronomico di Brera we are developing new technologies for the construction of low-weight X-ray optics based on Silicon Carbide and Alumina. The low-density of these materials in addition to their good mechanical characteristics can allow not only to fit the weight requirements but also to get a high angular resolution. The technique under development is based on the production of a ceramic carrier onto which it is epoxy replicated an Au layer previously deposited on the superpolished surface of a mandrel, the mandrel profile having the negative shape of the mirror optics. The bulk material of the mandrel is aluminum while its external surface is given by a thin layer (100 microns) of electroless Nickel. In the present paper we will describe very encouraging progresses that we recently obtained and we will propose this technique for the optics realization of future space projects.

We measure various spectral response characteristics around the oxygen and silicon K absorption edges of a Charge- Coupled Device X-ray detector used in the X-ray Imaging Spectrometer developed for the ASTRO-E mission. We have evaluated X-ray Absorption Fine Structure (XAFS) around oxygen K edge in detail. A strong absorption peak of 45% is confirmed just above the oxygen K edge and an oscillatory structure follows whose amplitude decreases from 20% at the edge to less than 1% at 0.9 keV. We also show XAFS and discuss on a change of the response function around the silicon K edge. The discontinuity of the signal pulse height at the silicon K edge is less than 1.8 eV. We determine the thickness of silicon, silicon dioxide, and silicon nitride in the dead layer using the depth of the absorption edge.

Two identical Wolter type 1 mandrels, with 50 cm diameter and 8.4 meter focal length, to be used by NASA/MSFC for their Constellation-X mirror development program, have been produced and tested by Carl Zeiss. In August 1999, both mandrels have been delivered to MSFC. Key optical performance of both mandrels: On-axis HEW; < 3.2 arc sec and micro-roughness: better than 0.30 nm RMS. We will report about mandrels design, fabrication, test and verification of their X-ray optical performance.

ESA's XEUS x-ray telescope design asks for segmented Wolter 1 mirror plates with radii up to 5 m and a focal length of 50 m. The mirror plates shall have an excellent optical performance (< 5 arcsec HEW). They shall be made by metal (e.g. Nickel) electroforming. This design approach requires highest quality segmented Wolter 1 mandrel plates, with an on-axis HEW < 2 arcsec and a micro-roughness better than 0.3 nm (rms). We will report about the novel design concept, fabrication approach and verification of the x-ray optical performance of the first XEUS demonstration mandrel.

Since 1974 X-ray optics and optical ground support equipment for various national and international X-ray and EUV- missions have been designed, manufactured, tested and delivered by Carl Zeiss/Oberkochen. The range of X-ray optics includes mirror systems for ASTRO 8, ROSAT and ABRIXAS, as well as mandrels for SAX, JET-X, WFXT, XMM, Constellation-X and XEUS. An example for high quality EUV- systems is the Wolter II mirror system for SOHO-CDS. We will give a retrospect to previous programs, report about recently performed and finished X-ray optics, as well as we will give an outlook for future contributions.

The main features of silicon drift detector modules currently produced by KETEK GmbH and MPI Halbleiterlabor, Munich will be summarized, giving an overview over state of the art and future possible applications.

Silicon Drift Detectors (SDDs) with integrated readout transistor combine a large sensitive area with a small value of the output capacitance and are therefore well suited for high resolution, high count rate X-ray spectroscopy. The low leakage current level obtained by the elaborated process technology makes it possible to operate them at room temperature or with moderate cooling. The monolithic combination of a number of SDDs to a Multichannel Drift Detector solves the limitation in size of the single device and allows the realization of new physics experiments and systems. The description of the device principle is followed by the introduction of the Multichannel Drift Detector concept. Layout, performance, and examples of current and future applications are given.

Silicon Drift Detectors (SDDs) have been recently employed as scintillation detectors for (gamma) -ray spectroscopy and imaging applications. With respect to conventional PMTs, these devices offer the higher quantum efficiency to the scintillation light, typical of a silicon detector. Moreover, thanks to the low value of output capacitance, a SDD is characterized by a lower electronics noise with respect to a conventional silicon photodiode. This feature allows a detector based on the CsI(Tl)-SDD architecture to reach high energy and position resolution in gamma detection. In this work we present the results obtained in the development of a first prototype of gamma detector for 1D position measurements and of a first prototype of small gamma camera for 2D position measurements, both detectors based on a single scintillator coupled to an array of SDDs.

A 64 X 64 pixel matrix prototype has been produced at the HLL. We will describe the test system setup and present measurements which characterize the performance.

NASA's Chandra X-ray Observatory includes a Flight Contamination Monitor (FCM), a system of 16 radioactive calibration sources mounted to the inside of the Observatory's forward contamination cover. The purpose of the FCM is to verify the ground-to-orbit transfer of the Chandra flux scale, through comparison of data acquired during the ground calibration with those obtained in orbit, immediately prior to opening the Observatory's sun-shade door. Here we report results of these measurements, which place limits on the change in mirror-detector system response and, hence, on any accumulation of molecular contamination on the mirror's iridium-coated surfaces.

The ability of periodic and aperiodic multilayer structures to diffract x-rays at grazing angles has long been understood, and has been successfully exploited in the x-ray region, primarily on flat substrates. We have recently begun producing Pt/C multilayer coated thin foil mirrors for the InFOC(mu) S balloon mission. The mirrors are made by depositing the multilayer on glass mandrels and transferring the multilayer to the thin foil substrates using a replication process similar to that used for production of the recently lost ASTRO-E mirrors. Both periodic and broadband versions have been successfully replicated onto thin foils and characterized by grazing incidence x-ray scattering. Initial comparisons between mirrors deposited on flat float glass substrates and mirrors replicated onto thin foils indicate that the reflection properties of the multilayer are not damaged by the transfer from mandrel to foil. We describe the production and characterization facilities that have been developed in our lab, and the performance of our multilayer mirrors, with particular emphasis on the characterization of interfaces in the Pt/C system.

We have measured the hard X-ray reflectivity and imaging performance from depth graded W/Si multilayer coated mirror segments mounted in a single reflection cylindrical prototype for the hard X-ray telescopes to be flown on the High Energy Focusing Telescope (HEFT) balloon mission. Data have been obtained in the energy range from 18 - 170 keV at the European Synchrotron Radiation Facility and at the Danish Space Research Institute at 8 keV. The modeling of the reflectivity data demonstrate that the multilayer structure can be well described by the intended power law distribution of the bilayer thicknesses optimized for the telescope performance and we find that all the data is consistent with an interfacial width of 4.5 angstroms. We have also demonstrated that the required 5% uniformity of the coatings is obtained over the mirror surface and we have shown that it is feasible to use similar W/Si coatings for much higher energies than the nominal energy range of HEFT leading the way for designing Gamma-ray telescopes for future astronomical applications. Finally we have demonstrate 35 arcsecond Half Power Diameter imaging performance of the one bounce prototype throughout the energy range of the HEFT telescopes.

The FAR.XITE is a proposed balloon payload. After a test flight, our initial goal is to fly 10 nested mirror modules, but then even more modules can be added until the mass limit of the pointing system and balloon gondola are reached. These limits are yet to be determined. In our design, Wolter I mirrors are coated with multilayers that allow FAR.XITE to reach 100 keV with better than 1 arc minute angular resolution. We summarize the science objectives, optical design and specifications that were previously reported, and present our recent results of advances in X-ray mirror and detector.

The aspect system of the Chandra Observatory plays a key role in realizing the full potential of Chandra's X-ray optics and detectors. To achieve the highest spatial and spectral resolution (for grating observations), an accurate post-facto time history of the spacecraft attitude and internal alignment is needed. The CXC has developed a suite of tools which process sensor data from the aspect camera assembly and gyroscopes, and produce the spacecraft aspect solution. In this poster, the design of the aspect pipeline software is briefly described, followed by details of aspect system performance during the first eight months of flight. The two key metrics of aspect performance are: image reconstruction accuracy, which measures the X-ray image blurring introduced by aspect; and celestial location, which is the accuracy of detected source positions in absolute sky coordinates.

The pointing control and aspect determination subsystem of the Chandra X-ray Observatory plays a key role in realizing the full potential of Chandra's X-ray optics and detectors. We review the performance of the spacecraft hardware components and sub-systems, which provide information for both real time control of the attitude and attitude stability of the Chandra Observatory and also for more accurate post-facto attitude reconstruction. These flight components are comprised of the aspect camera (star tracker) and inertial reference units (gyros), plus the fiducial lights and fiducial transfer optics which provide an alignment null reference system for the science instruments and X-ray optics, together with associated thermal and structural components. Key performance measures will be presented for aspect camera focal plane data, gyro performance both during stable pointing and during maneuvers, alignment stability and mechanism repeatability.

The Chandra X-ray Observatory (CXO) was launched on July 23, 1999 and reached its final orbit on August 7, 1999. The CXO is in a highly elliptical orbit, approximately 140,000 km X 10,000 km, and has a period of approximately 63.5 hours (approximately equals 2.65 days). It transits the Earth's Van Allen belts once per orbit during which no science observations can be performed due to the high radiation environment. The Chandra X-ray Observatory Center currently uses the National Space Science Data Center's `near Earth' AP-8/AE-8 radiation belt model to predict the start and end times of passage through the radiation belts. However, our scheduling software uses only a simple dipole model of the Earth's magnetic field. The resulting B, L magnetic coordinates, do not always give sufficiently accurate predictions of the start and end times of transit of the Van Allen belts. We show this by comparing to the data from Chandra's on-board radiation monitor, the EPHIN (Electron, Proton, Helium Instrument particle detector) instrument. We present evidence that demonstrates this mis-timing of the outer electron radiation belt as well as data that also demonstrate the significant variability of one radiation belt transit to the next as experienced by the CXO. We also present an explanation for why the dipole implementation of the AP-8/AE-8 model is not ideally suited for the CXO. Lastly, we provide a brief discussion of our on-going efforts to identify a model that accounts for radiation belt variability, geometry, and one that can be used for observation scheduling purposes.

We have analyzed data acquired during the Orbital Activation and Checkout (OAC) and Guest Observer (GO) phases of the Chandra X-ray Observatory mission in order to characterize the background of the Advanced CCD Imaging Spectrometer (ACIS) instrument produced by energetic particles. The ACIS instrument contains 8 Front-Illuminated (FI) CCDs and 2 Back-Illuminated (BI) CCDs. The FI and BI CCDs exhibit dramatically different responses to enhancements in the particle flux. The FI CCDs show relatively little increase in the overall count rate, typical increases are 1 - 5 cts s^-1 above the quiescent level; the BI CCDs can show large excursions to a s high as 100 cts s^-1 above the quiescent level. The durations of these intervals of enhanced background are also highly variable ranging from 500 s to 10⁴ s. These periods of enhanced background are sometimes but not always associated with increased particle flux when Chandra is near the radiation belts. We see evidence for a weak correlation with the low-energy electron channel of the Electron, Proton, Helium Instrument particle detector instrument on-board Chandra. We present some of the most extreme examples of these background enhancements identified to this point in the mission.

The High Energy Focusing Telescope (HEFT) is a balloon-borne experiment employing focusing optics in the hard X-ray/soft gamma-ray band (20 - 100 keV) for sensitive observations of astrophysical sources. The primary scientific objectives include imaging and spectroscopy of ⁴⁴Ti emission in young supernova remnants, sensitive hard X-ray observations of obscured Active Galactic Nuclei, and spectroscopic observations of accreting high-magnetic field pulsars. Over the last four years, we have developed grazing-incidence depth-graded multilayer optics and high spectral resolution solid stat Cadmium Zinc Telluride pixel detectors in order to assemble a balloon-borne experiment with sensitivity and imaging capability superior to previous satellite missions operating in this band. In this paper, we describe the instrument design, and present recent laboratory demonstrations of the optics and detector technologies.

The Chandra X-ray Observatory was successfully launched on July 23, 1999, and subsequently began an intensive calibration phase. We present preliminary results from in- flight calibration of the low energy response of the High Resolution Camera Spectroscopic readout (HRC-S) combined with the Low Energy Transmission Grating (LETG) aboard Chandra. These instruments comprise the Low Energy Transmission Grating Spectrometer (LETGS). For this calibration study, we employ a pure hydrogen non-LTE white dwarf emission model (T_eff equals 25000 K and log g equals 9.0) for comparison with the Chandra observations of Sirius B. Pre-flight calibration of the LETGS effective area was conducted only at wavelengths shortward of 45 angstroms (E > 0.277 keV). Our Sirius B analysis shows that the HRC-S quantum efficiency (QE) model assumed for longer wavelengths overestimates the effective area on average by a factor of 1.6. We derive a correction to the low energy HRC-S QE model to match the predicted and observed Sirius B spectra over the wavelength range of 45 - 185 angstroms. We make an independent test of our results by comparing a Chandra LETGS observation of HZ 43 with pure hydrogen model atmosphere predictions and find good agreement.

Test and alignment of light weight X-ray optics have been a challenge for two reasons: (1) that the intrinsic mirror quality and distortions caused by handling can not be easily separated, and (2) the diffraction limits of the visible light become a severe problem at the order of one arc- minute. Traditional methods of using a normal incident pencil or small parallel beam which monitors a tiny fraction of the mirror in question at a given time can not adequately monitor those distortions. We are developing a normal incidence setup that monitors a large fraction, if not the whole, of the mirror at any given time. It allow us to test and align thin X-ray mirrors to an accuracy of a few arc seconds or to a limit dominated by the mirror intrinsic quality.

Front side illuminated CCDs comprising focal plane of Chandra X-ray telescope have suffered some radiation damage in the beginning of the mission. Measurements of CTI and dark current at different temperatures led us to conclusion that the type of damage is inconsistent with the much studied type of damage created by protons with energies higher than 10 MeV. Intensive ground based investigation showed that irradiation of CCD with low energy protons (about 100 keV) results in the device characteristics very similar to the ones of the flight chips (very low dark current, the shape of the CTI temperature dependence). We were able to reliably determine that only image section of the flight chips was damaged and therefore only fast transfer from image to frame store section was affected. We have developed several techniques in order to determine the parameters of the electron traps introduced into the transfer channel of the irradiated device.

On 10th December 1999, the European X-ray satellite XMM, now called XMM-Newton, was successfully put into orbit. After initial commissioning of the satellite's subsystems, the EPIC-pn camera was switched on and tested thoroughly in the period Jan./Febr. 2000. After refining of some of the parameter settings and the on-board pn-computer programs, we started the Calibration and Performance Verification Phase, which will last until the end of May 2000. In this paper we report on the results of the EPIC-pn Commissioning Phase with respect to the in-orbit performance of the camera. We also show some of the early results with the pn-camera, the first light image of a region in the Large Magellanic Cloud, and an observation of the Crab Nebular.

XMM-Newton, the most powerful X-ray telescope ever built was launched from the european space port Kourou on december 10 last year. Three large X-ray Wolter type mirror systems are focusing the incoming X-rays from 100 eV up to 15,000 eV onto the focal instruments: fully depleted backside illuminated pn-CCDs and frontside illuminated MOS-CCDs. The concept of the pn-CCD camera will be briefly described and its performance on ground and in orbit will be shown. Special emphasis will be given to the radiation hardening of the devices, to the instrument background and to the experience of charged particle background in space. A comparison of the performance on ground and after 5 months in space will be shown.

The in-orbit imaging performance of the three X-ray telescopes on board of the X-ray astronomy observatory XMM- Newton is presented and compared with the performance measured on ground at the MPE PANTER test facility. The comparison shows an excellent agreement the on ground and in-orbit performance.