The primary scientific mission of the Black Hole Finder Probe (BHFP), part of the NASA Beyond Einstein program, is to survey the local Universe for black holes over a wide range of mass and accretion rate. One approach to such a survey is a hard X-ray coded-aperture imaging mission operating in the 10-600 keV energy band, a spectral range that is considered to be especially useful in the detection of black hole sources. The development of new inorganic scintillator materials provides improved performance (for example, with regards to energy resolution and timing) that is well suited to the BHFP science requirements. Detection planes formed with these materials coupled with a new generation of readout devices represent a major advancement in the performance capabilities of scintillator-based gamma cameras. Here, we discuss the Coded Aperture Survey Telescope for Energetic Radiation (CASTER), a concept that represents a BHFP based on the use of the latest scintillator technology.

We flew a prototype of the Nuclear Compton Telescope (NCT) on a high altitude balloon from Fort Sumner, New Mexico on 2005 June 1. The NCT prototype is a soft gamma-ray (0.2-15 MeV) telescope designed to study, through spectroscopy, imaging, and timing, astrophysical sources of nuclear line emission and gamma-ray polarization. Our program is designed to develop and test the technologies and analysis techniques crucial for the Advanced Compton Telescope satellite, while studying gamma-ray radiation with very high spectral resolution, moderate angular resolution, and high sensitivity. The NCT prototype utilizes two, 3D imaging germanium detectors (GeDs) in a novel, ultra-compact design optimized for nuclear line emission (0.5-2 MeV) and polarization in the 0.2-0.5 MeV range. Our prototype flight was a critical test of the novel instrument technologies, analysis techniques, and background rejection procedures we have developed for high resolution Compton telescopes.

Various X-ray satellites have used the Crab as a standard candle to perform their calibrations in the past. The calibration of XMM-Newton, however, is independent of the Crab nebula, because this object has not been used to adjust spectral calibration issues. In 2004 a number of special observations were performed to measure the spectral parameters and the absolute flux of the Crab with XMM-Newton's EPIC-pn CCD camera. We describe the results of the campaign in detail and compare them with data of four current missions (Integral, Swift, Chandra, RXTE) and numerous previous missions (ROSAT, EXOSAT, Beppo-SAX, ASCA, Ginga, Einstein, Mir-HEXE).

The Medium Energy Gamma-ray Astronomy (MEGA) telescope concept will soon be proposed as a MIDEX mission. This mission would enable a sensitive all-sky survey of the medium-energy gamma-ray sky (0.4 - 50 MeV) and bridge the huge sensitivity gap between the COMPTEL and OSSE experiments on the Compton Gamma Ray Observatory, the SPI and IBIS instruments on INTEGRAL, and the visionary Advanced Compton Telescope (ACT) mission. The scientific goals include, among other things, compiling a much larger catalog of sources in this energy range, performing far deeper searches for supernovae, better measuring the galactic continuum and line emissions, and identifying the components of the cosmic diffuse gamma-ray emission. MEGA will accomplish these goals using a tracker made of Si strip detector (SSD) planes surrounded by a dense high-Z calorimeter. At lower photon energies (below ~ 30 MeV), the design is sensitive to Compton interactions, with the SSD system serving as a scattering medium that also detects and measures the Compton recoil energy deposit. If the energy of the recoil electron is sufficiently high (> 2 MeV) its momentum vector can also be measured. At higher photon energies (above ~ 10 MeV), the design is sensitive to pair production events, with the SSD system measuring the tracks of the electron and positron. A prototype instrument has been developed and calibrated in the laboratory and at a gamma-ray beam facility. We present calibration results from the prototype and describe the proposed satellite mission.

The XEUS (X-ray Evolving Universe Spectroscopy) mission is designed to explore the X-ray emission from objects in the Universe at high red shifts. A core set of instruments has been selected that allows the scientific goals of the mission to be met. It comprises narrow field imaging spectrometers of both Transition Edge Sensor (TES) and Superconducting Tunnel Junction (STJ) designs, and a Wide Field Imager with novel Silicon Active - Pixel sensing elements. We discuss the additional science goals for XEUS such as high time resolution, polarimetry and extensions to high energies >10keV, and the additional instruments with modest resource requirements which may facilitate these goals.

The X-ray Evolving Universe Spectroscopy (XEUS) mission [1,2] is under study by ESA and JAXA in preparation for inclusion in the ESA long term Science Programme (the Cosmic Vision 2015-2025 long-term plan). With very demanding science requirements, missions such as XEUS can only be implemented for acceptable costs, if new technologies and concepts are applied. The identification of the key technologies to be developed is one of the drivers for the early mission design studies, and in the case of XEUS this has led to the development of a novel approach to building X-ray optics for ambitious future high-energy astrophysics missions [3,4]. XEUS is based on a single focal plane formation flying configuration, building on a novel lightweight X-ray mirror technology. With a 50 m focal length and an effective area of 10 m² at 1 keV this observatory is optimized for studies of the evolution of the X-ray universe at moderate to high redshifts. This paper describes the current status of the XEUS mission design, the accommodation of the large optics, the corresponding deployment sequence and the associated drivers, in particular regarding the thermal design of the ystem. The main results were obtained in two Concurrent Design Facility (CDF) studies and other internal activities at ESTEC.

The Energetic X-ray Survey Telesccope (EXIST) is under study for the propsed Black Hole Finder Probe, one of the three Einstein Probe missions in NASA's proposed Beyond Einstein Program. EXIST would have the capability to survey the full sky at 5-600 keV and enable black holes to be surveyed and studied on all scales. In particular, GRB's will be located at sensitivities and bandwidths much greater than with previous missions and likely yield constraints on the massive population III black holes. The measurements of hard X-ray polarization, thus far relatively unexplored, could also provide important clues about the GRB progenitor. In this paper, we report on the preliminary estimates to the sensitivity to GRB polarization with EXIST.

The great collecting area of the mirrors coupled with the high quantum efficiency of the EPIC detectors have made XMM-Newton the most sensitive X-ray observatory flown to date. This is particularly evident during slew exposures which, while giving only 15 seconds of on-source time, actually constitute a 2-10 keV survey ten times deeper than current "all-sky" catalogues. Here we report on progress towards making a catalogue of slew detections constructed from the full, 0.2-12 keV energy band and discuss the challenges associated with processing the slew data. The fast (90 degrees per hour) slew speed results in images which are smeared, by different amounts depending on the readout mode, effectively changing the form of the point spread function. The extremely low background in slew images changes the optimum source searching criteria such that searching a single image using the full energy band is seen to be more sensitive than splitting the data into discrete energy bands. False detections due to optical loading by bright stars, the wings of the PSF in very bright sources and single-frame detector flashes are considered and techniques for identifying and removing these spurious sources from the final catalogue are outlined. Finally, the attitude reconstruction of the satellite during the slewing maneuver is complex. We discuss the implications of this on the positional accuracy of the catalogue.

We are currently investigating techniques to improve the count rate and time resolution of microchannel plates (MCPs) and high speed electronic image readout schemes, as the basis for the development of high performance imaging MCP detectors for space science and other disciplines. We discuss the factors limiting the ultimate count rate and time resolution of MCP detectors and review the potential of techniques such as bulk conductive glass in MCP manufacture, and the advantages conferred by small MCP pore size. We present test results indicating the improved time resolution achievable using small pore MCPs. We review developments in readout design to increase performance for high throughput detectors, and which are capable of providing suitable combinations of attributes for specific applications, including high spatial resolution, high time resolution, high count rate, and parallel event processing for detection of simultaneous events. High throughput techniques require an increase in processing channel density and we discuss how this may be achieved by integration of the readout with the electronics package. The design and manufacture of readout systems using integrated ASIC based electronics is discussed and projected performance is presented. Such devices also have uses over a wide range of other scientific disciplines, and we discuss applications ranging from biomedicine to synchrotron physics.

The development of high quantum efficiency photemissive detectors is recognized as a significant advancement for astronomical missions requiring photon-counting detection. For solar-blind NUV detection, current missions (GALEX, STIS) using Cs₂Te detectors are limited to ~10% DQE. Emphasis in recent years has been to develop high QE (>50%) GaN and AlGaN photocathodes (among a few others) that can then be integrated into imaging detectors suitable for future UV missions. We report on progress we have made in developing GaN photocathodes and discuss our observations related to parameters that effect efficiency and stability, including intrinsic material properties, surface preparation, and vacuum environment. We have achieved a QE in one case of 65% at 185 nm and are evaluating the stability of these high QEs. We also discuss plans for incorporating photocathodes into imaging and non-imaging sealed devices in order to demonstrate long term stability.

We have made InGaN:Mg epitaxial layers and report for the first time the QE versus wavelength for a photo-cathode. The motivation for InGaN is to lower the band gap just enough to enable detection of nitrogen fluorescence 337 nm, 357 nm and 391nm for both Earth observing and for energetic cosmic ray studies. Homogeneous InGaN alloys are difficult to prepare as the indium rich alloy tends to coalesce into quantum dots. The transmission, X-ray, and photo-luminescence measurements of the films indicated a significant concentration of Mg acceptors was incorporated into the film and as such could be converted into a viable photo-cathode upon cessiation. We present our photo-luminescence, X-ray, and near-field scanning microscope (NSOM) and QE measurements of films and compare these with measurements of GaN:Mg. The spectral properties of the photo-cathodes will also be presented.

Microchannel plates have been used over many years in astronomical applications for X-ray, UV and visible sensing. Their adaptability to various size and configuration formats have allowed a wide range of devices to be realized, employing many different forms of readout techniques and photocathode types. One problem that has arisen for a number of these programs is the issue of obtaining high quantum efficiency on a consistent basis. Several missions have suffered from problems when microchannel plates have not achieved the quantum efficiency values that are the generally accepted normal values. We have compiled an extensive set of quantum efficiency measurements which cover missions and devices produced over the past 20 years. These show that the deficiencies in MCP QE of bare MCP's also result in a corresponding decrease in QE for same MCP's coated with a photocathode. This may be interpreted as a deficiency of the MCP detection efficiency for low energy photoelectrons produced by the MCP/cathode. Recent measurements of MCP's produced by alteration of the processing procedures shows that this problem is avoidable, and gives excellent results for current generation MCP's with 5-6 micron pore sizes.

We present a review on the research carried out with the Micro-Hole & Strip plate (MHSP) gaseous electron multiplier. In this new device charge multiplication occurs in two stages: radiation-induced electrons are multiplied in small holes and the resulting avalanche is further multiplied on anode strips patterned on the multiplier's bottom electrode. This structure provides fast multiplication process, has a high total gain even in noble gas mixtures and provides good localization properties. Detectors based on this principle have shown gains above 10⁴ and energy resolution of about 14% for 5.9-keV X-rays; large gains were obtained at high gas pressures as well, allowing for efficient detection of higher-energy X-rays. The properties of UV-photon detectors comprising an MHSP coupled to semitransparent CsI photocathodes or with reflective ones deposited on the multiplier's top surface were investigated. The operation mechanism of these detectors and their most significant results are presented.

The Polarized Gamma-ray Observer (PoGO) is a new balloon-borne instrument designed to measure polarization from astrophysical objects in the 30-200 keV range. It is under development for the first flight anticipated in 2008. PoGO is designed to minimize the background by an improved phoswich configuration, which enables a detection of 10 % polarization in a 100 mCrab source in a 6--8 hour observation. To achieve such high sensitivity, low energy response of the detector is important because the source count rate is generally dominated by the lowest energy photons. We have developed new PMT assemblies specifically designed for PoGO to read-out weak scintillation light of one photoelectron (1 p.e.) level. A beam test of a prototype detector array was conducted at the KEK Photon Factory, Tsukuba in Japan. The experimental data confirm that PoGO can detect polarization of 80-85 % polarized beam down to 30 keV with a modulation factor 0.25 ± 0.05.

Inorganic scintillators such as NaI(Tl) and CsI(Na) have been used extensively in hard x-ray and low-energy gamma-ray imaging systems. Recently, a new generation of scintillators has been developed with properties that could greatly enhance the performance of such imaging systems. In particular, the lanthanum halides show great promise with increased light yield and peak emission at shorter wavelengths compared to NaI or CsI. Since these scintillators emit at relatively short wavelengths, wavelength-shifting fibers can be used which re-emit at wavelengths around 420 nm, providing a good match to bialkali photocathode response. Multi-anode photomultiplier tubes can be used to read out individual fibers from orthogonal layers to provide x-y position information, while energy measurements can be made by large area photomultiplier tubes. Such an arrangement potentially provides improved overall position and energy resolution and lower thresholds compared to imaging systems configured as standard NaI or CsI gamma cameras. We present measurements of the energy resolution obtained from lanthanum chloride (LaCl₃) and lanthanum bromide (LaBr₃) scintillators viewed both perpendicular to the axis and down the length of square multi-clad wavelength-shifting fibers. These results are compared to a standard NaI detector with wavelength-shifting fibers. The implications of these results for gamma-ray imaging will then be discussed.

We describe our program to develop gas micro-well detectors (MWDs) as three-dimensional charged particle trackers for use in advanced gamma-ray telescope concepts. A micro-well detector consists of an array of individual micro-patterned gas proportional counters opposite a planar drift electrode. The well anodes and cathodes may be connected in X and Y strips, respectively, to provide two-dimensional imaging. When combined with transient digitizer electronics, which record the time signature of the charge collected in the wells of each strip, full three-dimensional reconstruction of charged-particle tracks in large gas volumes is possible. Such detectors hold great promise for advanced Compton telescope (ACT) and advanced pair telescope (APT) concepts due to the very precise measurement of charged particle momenta that is possible (Compton recoil electrons and electron-positron pairs, respectively). We present preliminary lab results, including detector fabrication, prototype electronics, and initial detector testing. We also discuss applications to the ACT and APT mission concepts, based on GEANT3 and GEANT4 simulations.

The PICsIT (PIxelated CsI Telescope) instrument is the high energy plane of the IBIS imager onboard the INTEGRAL satellite. PICsIT consists of a 64x64 detector array, each composed of a CsI(Tl) scintillating crystal with p-i-n photodiode readout. Since its first in-orbit activation, several extended tracks have been detected in its images, indicating the presence of frequent electromagnetic and hadronic showers initiated by primary cosmic rays. In this paper we present the peculiar way the showers can form images in the PICsIT detector plane. We show also as the rejection of tracks events can be accomplished thanks to their peculiar geometrical and timing characteristics.

We outline our plan to develop ProtoEXIST, a balloon-borne prototype experiment for the Energetic X-ray Imaging Survey Telescope (EXIST) for the Black Hole Finder Probe. EXIST will consist of multiple wide-field hard X-ray coded-aperture telescopes. The current design of the EXIST mission employs two types of telescope systems: high energy telescopes (HETs) using CZT detectors, and low energy telescopes (LETs) using Si detectors. With ProtoEXIST, we will develop and demonstrate the technologies required for the EXIST HETs. As part of our development efforts, we also present recent laboratory measurements of the spectral response and efficiency variation of imaging CZT detectors on a fine scale (~0.5 mm). The preliminary results confirm the need for multi-pixel readouts and small inter-pixel gaps to achieve uniform spectral response and high detection efficiency across detectors.

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 m²) 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 X-ray observatory XMM-Newton is now in orbit for more than 5 years. The performance of the EPIC-pn CCD camera has been monitored since and its calibration has been improved steadily. We report in this presentation on our recent investigations in different calibration issues: Data of the on-board Fe-55 calibration source were used for monitoring the charge transfer efficiency (CTE) degradation. A special calibration observation of the line-rich supernova remnant Cas-A in the extended Full Frame Mode was used to refine the energy calibration in this mode. Together with ground measurements, a non-routine observation of the calibration target N132D will lead to an improvement of the CTE correction of the Large Window Mode.

Soon after launch, the Advanced CCD Imaging Spectrometer (ACIS), one of the focal plane instruments on the Chandra X-ray Observatory, suffered radiation damage from exposure to soft protons during passages through the Earth's radiation belts. Current operations require ACIS to be protected during radiation belt passages to prevent this type of damage, but there remains a much slower and more gradual increase. We present the history of ACIS charge transfer inefficiency (CTI), and other measures of radiation damage, from January 2000 through June 2005. The rate of CTI increase is low, of order 1e-6 per year, with no indication of step-function increases due to specific solar events. Based on the time history and CCD location of the CTI increase, we speculate on the nature of the damaging particles.

The CCDs on the Chandra X-ray Observatory are vulnerable to radiation damage from low-energy protons scattered off the telescope's mirrors onto the focal plane. Following unexpected damage incurred early in the mission, the Chandra team developed, implemented, and maintains a radiation-protection program. This program - involving scheduled radiation safing during radiation-belt passes, intervention based upon real-time space-weather conditions and radiation-environment modeling, and on-board radiation monitoring with autonomous radiation safing - has successfully managed the radiation damage to the CCDs. Since implementing the program, the charge-transfer inefficiency (CTI) has increased at an average annual rate of only 3.2×10-6 (2.3%) for the front-illuminated CCDs and 1.0×10-6 (6.7%) for the back-illuminated CCDs. This paper describes the current status of the Chandra radiation-management program, emphasizing enhancements implemented since the original paper.

On December 10th 2004 the XMM-Newton observatory celebrated its 5th year in orbit. Since the beginning of the mission steady health and contamination monitoring has been performed by the XMM-Newton SOC and the instrument teams. Main targets of the monitoring, using scientific data for all instruments on board, are the behaviour of the Charge Transfer Efficiency, the gain, the effective area and the bad, hot and noisy pixels. The monitoring is performed by combination of calibration observations using internal radioactive calibration sources with observations of astronomical targets. In addition a set of housekeeping parameters is continuously monitored reflecting the health situation of the instruments from an engineering point of view. We show trend behaviour over the 5 years especially in combination with events like solar flares and other events affecting the performance of the instruments.

The CAST experiment at CERN (European Organization of Nuclear Research) searches for axions from the sun. The axion is a pseudoscalar particle that was motivated by theory thirty years ago, with the intention to solve the strong CP problem. Together with the neutralino, the axion is one of the most promising dark matter candidates. The CAST experiment has been taking data during the last two years, setting an upper limit on the coupling of axions to photons more restrictive than from any other solar axion search in the mass range below 10^-1 eV. In 2005 CAST will enter a new experimental phase extending the sensitivity of the experiment to higher axion masses. The CAST experiment strongly profits from technology developed for high energy physics and for X-ray astronomy: A superconducting prototype LHC magnet is used to convert potential axions to detectable X-rays in the 1-10 keV range via the inverse Primakoff effect. The most sensitive detector system of CAST is a spin-off from space technology, aWolter I type X-ray optics in combination with a prototype pn-CCD developed for ESA's XMM-Newton mission. As in other rare event searches, background suppression and a thorough shielding concept is essential to improve the sensitivity of the experiment to the best possible. In this context CAST offers the opportunity to study the background of pn-CCDs and its long term behavior in a terrestrial environment with possible implications for future space applications. We will present a systematic study of the detector background of the pn-CCD of CAST based on the data acquired since 2002 including preliminary results of our background simulations.

A new generation of pnCCDs has been developed for the proposed X-ray astronomy missions, DUO and ROSITA. The DUO/ROSITA CCD is a frame store pnCCD based on the concept of the XMM-Newton pnCCD and has both, improved performance and new features. This detector permits accurate spectroscopy of X-rays as well as imaging and high time resolution with high quantum efficiency in the energy band from 0.3 keV to 10 keV. Interfering electron-hole pair generation due to optical and UV light is prevented by a deposition of an on-chip filter. We describe the frame store pnCCDs developed and fabricated for the DUO and ROSITA missions in the semiconductor laboratory of the Max-Planck-Institut fuer extraterrestrische Physik. An overview about the CCD concept and design is given along with some details about the fabrication of the devices. In addition, we introduce a new analog signal processor which has been developed specifically for the readout of the frame store pnCCD signals. The main focus of this paper is to present the very first measurements with this CCD type and its analog signal processor. Towards this aim we report the operation of this new sensor and its key performance parameters. Finally we discuss ongoing and future tests with the DUO/ROSITA CCDs.

DEPMOSFET based Active Pixel Sensor (APS) matrix devices, originally developed to cope with the challenging requirements of the XEUS Wide Field Imager, have proven to be a promising new imager concept for a variety of future X-ray imaging and spectroscopy missions like Simbol-X. The devices combine excellent energy resolution, high speed readout and low power consumption with the attractive feature of random accessibility of pixels. A production of sensor prototypes with 64 x 64 pixels with a size of 75 μm x 75 μm each has recently been finished at the MPI semiconductor laboratory in Munich. The devices are built for row-wise readout and require dedicated control and signal processing electronics of the CAMEX type, which is integrated together with the sensor onto a readout hybrid. A number of hybrids incorporating the most promising sensor design variants has been built, and their performance has been studied in detail. A spectroscopic resolution of 131 eV has been measured, the readout noise is as low as 3.5 e- ENC. Here, the dependence of readout noise and spectroscopic resolution on the device temperature is presented.

In recent years the XEUS mission concept has evolved and has been the subject of several industrial studies. The mission concept has now matured to the point that it could be proposed for a Phase A study and subsequent flight programme. The key feature of XEUS will be its X-ray optic with collecting area ~30-100x that of XMM. The mission is envisaged at an orbit around the L2 point in space, and is formed from two spacecraft; one for the mirrors, and the other for the focal plane detectors. With a focal length of 50m, the plate scale of the optic is 6.5x that of XMM, which using existing focal plane technology will reduce the effective field of view to a few arc minutes. Cryogenic instrumentation, with detector sizes of a few mm can only be used for narrow field studies of target objects, and a wide field instrument is under consideration using a DEPFET pixel array to image out to a diameter of 5 arcminutes, requiring an array of dimension 70mm. It is envisaged to extend this field of view possibly out to 15 arcminutes through the use of an outer detection ring comprised of MOS CCDs

Cute-1.7 is a pico-satellite mainly developed by students at Tokyo Institute of Technology (Tokyo Tech). This will be the second satellite built at Tokyo Tech after the first one, CUTE-I, which was launched in June 2003. The configuration of Cute-1.7 is a 10 cm × 10 cm × 20 cm box with a mass of 2 kg. The engineering objective of Cute-1.7 is to validate commercially available products such as Personal Digital Assistances (PDAs) in the space environment, and to demonstrate a "satellite core concept" which is dividing a satellite into a bus component and a mission component to adopt various missions. The scientific objective is to demonstrate the performance of avalanche photo diodes (APDs) as future X-ray detectors used in the space environment. Results of this mission will provide the first feedback for a space application of APD such as Japan's future X-ray astronomy mission NeXT.

The He+ ion provides a valuable tracer of solar wind dynamics and the heliospheric boundary. Mapping the heliosphere in the 30.4 nm resonance line of the He+ ion with high spectral resolution will open access to the heliopause and reveal the three-dimensional flow of the solar wind. The emission fluxes are however faint, just a few mR, which poses a serious limitation on the mapping rate at high signal-to-noise ratio. We have developed a spectrometer configuration for narrowband EUV emission that offers important advantages over previous designs: high throughput (~1cps/mR), high resolution (several thousand), no moving parts, and modest instrument size and mass. The concept combines a conventional normal-incidence Rowland mount grating and an efficient multilayer coating, with a microchannel plate detector performing two dimensional photon counting. One key innovation is the use of a large-area multi-slit at the spectrometer entrance. This multislit is a one dimensional sequence of open and opaque zones, against which pattern the accumulated spectral image can be correlated to recover the incident spectrum. The other innovation is arranging that each member of the multislit group is curved in such a way that the off-plane grating aberrations (which extend and rotate the image of each object point) do not introduce significant wavelength broadening. The curved slit arrangement yields a large well-corrected image field, and a high throughput for diffuse emission is achieved. The curved-multislit Rowland spectrometer may have a variety of other applications sensing diffuse fluxes with high spectral resolution.

We describe the use of Externally Dispersed Interferometry (EDI) for high-resolution absorption spectroscopy. By adding a small fixed-delay interferometer to a dispersive spectrograph, a precise fiducial grid in wavelength is created over the entire spectrograph bandwidth. The fiducial grid interacts with narrow spectral features in the input spectrum to create a moire pattern. EDI uses the moire pattern to obtain new information about the spectra that is otherwise unavailable, thereby improving spectrograph performance. We describe the theory and practice of EDI spectrometers and demonstrate improvements in the spectral resolution of conventional spectrographs by a factor of 2 to 6. The improvement of spectral resolution offered by EDI can readily benefit space instruments operating from the near IR to the far UV by reducing spectrograph size or increasing instantaneous bandwidth.

In the context of the NASA balloon borne experiment named Fireball (Faint Intergalactic Redshifted Emission BALLoon) dedicated to map the Intergalactic Medium, we designed a fiber-fed near ultraviolet spectrograph to work in the 200 nm atmospheric transmission window. We first describe the system level optimization leading to the atypical use in UV of a fiber Integral Field Unit at the focus of a one meter diameter parabolic mirror. For the qualification of the design we measured the absolute transmission of an UV polyimide 100 microns core fiber. The fiber bundle made of 400 fibers rearranged in a 50 mm slit feeds an F/2.5 spectrograph based on an Offner Littrow mount. We present the optical performances of this design with a high throughput and a well matched aperture ratio.

During its first 6 years of operation, the cold (-60°C) optical blocking filter of the Advanced CCD Imaging Spectrometer (ACIS), on board the Chandra X-ray Observatory, has accumulated a contaminating layer that attenuates the low-energy x rays. To assist in assessing the likelihood of successfully baking off the contaminant, members of the Chandra team developed contamination-migration simulation software. The simulation follows deposition onto and (temperature-dependent) vaporization from surfaces comprising a geometric model of the Observatory. A separate thermal analysis, augmented by on-board temperature monitoring, provides temperatures for each surface of a similar geometric model. This paper describes the physical basis for the simulations, the methodologies, and the predicted migration of the contaminant for various bake-out scenarios and assumptions.

The XRT is a sensitive, autonomous X-ray imaging spectrometer onboard the Swift Gamma-Ray Burst Observatory. The unique observing capabilities of the XRT allow it to autonomously refine the Swift BAT positions (~1-4' uncertainty) to better than 2.5 arcsec in XRT detector coordinates, within 5 seconds of target acquisition by the Swift Observatory for typical bursts, and to measure the flux, spectrum, and light curve of GRBs and afterglows over a wide dynamic range covering more than seven orders of magnitude in flux (62 Crab to < 1 mCrab). The results of the rapid positioning capability of the XRT are presented here for both known sources and newly discovered GRBs, demonstrating the ability to automatically utilise one of two integration times according to the burst brightness, and to correct the position for alignment offsets caused by the fast pointing performance and variable thermal environment of the satellite as measured by the Telescope Alignment Monitor. The onboard results are compared to the positions obtained by groundbased follow-up. After obtaining the position, the XRT switches between four CCD readout modes, automatically optimising the scientific return from the source depending on the flux of the GRB. Typical data products are presented here.

The Swift X-ray Telescope (XRT) is a CCD based X-ray telescope designed for localization, spectroscopy and long term light curve monitoring of Gamma-Ray Bursts and their X-ray afterglows. Shortly after launch there was a failure of the thermo-electric cooler on the XRT CCD. Due to this the Swift XRT Team had the unexpected challenge of ensuring that the CCD temperature stayed below -50C utilizing only passive cooling through a radiator mounted on the side of the Swift. Here we show that the temperature of the XRT CCD is correlated with the average elevation of the Earth above the XRT radiator, which is in turn related to the targets that Swift observes in an orbit. In order to maximize passive cooling of the XRT CCD, the XRT team devised several novel methods for ensuring that the XRT radiator's exposure to the Earth was minimized to ensure efficient cooling. These methods include: picking targets on the sky for Swift to point at which are known to put the spacecraft into a good orientation for maximizing XRT cooling; biasing the spacecraft roll angle to point the XRT radiator away from the Earth as much as possible; utilizing time in the SAA, in which all of the instruments on-board Swift are non-operational, to point at "cold targets"; and restricting observing time on "warm" targets to only the periods at which the spacecraft is in a favorable orientation for cooling. By doing this at the observation planning stage we have been able to minimize the heating of the CCD and maintain the XRT as a fully operational scientific instrument, without compromising the science goals of the Swift mission.

The Swift X-ray Telescope (XRT) focal plane camera is a front-illuminated MOS CCD, providing a spectral response kernel of 144 eV FWHM at 6.5 keV. We describe the CCD calibration program based on celestial and on-board calibration sources, relevant in-flight experiences, and developments in the CCD response model. We illustrate how the revised response model describes the calibration sources well. Loss of temperature control motivated a laboratory program to re-optimize the CCD substrate voltage, we describe the small changes in the CCD response that would result from use of a substrate voltage of 6V.

The Swift X-ray Telescope (XRT) is designed to make astrometric, spectroscopic and photometric observations of the X-ray emission from Gamma-ray bursts and their afterglows, in the energy band 0.2-10 keV. Swift was successfully launched on 2004 November 20. Here we report the results of the analysis of Swift XRT Point Spread Function (PSF) as measured in the first four months of the mission during the instrument calibration phase. The analysis includes the study of the PSF of different point-like sources both on-axis and off-axis with different spectral properties. We compare the in-flight data with the expectations from the on-ground calibration. On the basis of the calibration data we built an analytical model to reproduce the PSF as a function of the energy and the source position within the detector which can be applied in the PSF correction calculation for any extraction region geometry.

The Swift X-ray Telescope (XRT) is designed to make astrometric, spectroscopic and photometric observations of the X-ray emission from Gamma-ray bursts and their afterglows in the 0.2-10 keV energy band. Here we report the initial results of the analysis of Swift XRT effective area as measured both on-axis and off-axis during the in-flight calibration phase using the laboratory results and ray-tracing simulations as a starting point. Our analysis includes the study of the effective area at a range of energies, for different event grade selection and operating modes using two astronomical sources characterized by different intrinsic spectra.

The X-ray telescope (XRT) on board Swift, launched on 2004 Nov 20, is performing astrometric, spectroscopic and photometric observations of the X-ray emission from Gamma-ray burst afterglows in the energy band 0.2-10 keV. In this paper, we describe the results of the in-flight calibration relative to the XRT timing resolution and absolute timing capabilities. The timing calibration has been performed comparing the main pulse phases of the Crab profile obtained from several XRT observations in Low Rate Photodiode and Windowed Timing mode with those from contemporaneous RXTE observations. The XRT absolute timing is well reproduced with an accuracy of 200 μs for the Low Rate Photodiode and 300 μs for the Windowed Timing mode.

The Ultraviolet and Optical telescope (UVOT) is one of the three instruments on board of the SWIFT observatory. UVOT is on the cutting edge of our ability to observe and eventually help scientists to understand gamma-ray bursts. As any space-based telescope it requires both pre-flight and on-orbit calibrations. This paper is the first of a pair of papers presenting the initial on-board calibration of the UVOT. In particular, we'll discuss distortion, large and small scale sensitivity variations and the telescope point spread function.

The Ultraviolet and Optical telescope (UVOT) on board the SWIFT observatory, plays an important part in the quest to understand gamma-ray bursts. As its name suggests, the UVOT obtains ultraviolet and optical data at high time resolution, with 7 broad band filters and 2 low resolution grisms. This paper forms the second of a pair of papers presenting the initial on-board calibration of the UVOT. The first one (Part 1) deals with distortion, large and small scale sensitivity variations and the telescope point spread function. In this paper we cover the following topics: the photometry of the broadband filters including colour transformations and linearity; the wavelength calibration and sensitivities of the grisms; time resolution and red leak.

Monitor of All-sky X-ray Image(MAXI) is an X-ray all sky monitor, which will be attached to the Japanese Experiment Module (JEM) on the International Space Station (ISS) around the year 2008. MAXI carries two types of scientific instruments. The Gas Slit Camera(GSC) consists of twelve Xe filled one-dimensional position sensitive gas proportional counters sensitive to X-ray in 2-30 keV band. The Solid-state Slit Camera (SSC) is a set of X-ray CCD arrays sensitive to 0.5-10 keV photons. Both detectors are utilized in combination with a slit and orthogonally arranged collimator plates to produce one-dimensional X-ray images along sky great circles. The instruments are now under fabrication and preflight testing. A detector response matrix (DRM) of GSC is also under development phase based on flight model calibration tests for counters and collimators. MAXI's overall performance depends on not only hardware characteristics but on the fact that the field-of-view changes in time even during observations. To study this complicated situation, we are developing a software, DRM builder, and also a simulation software to evaluate "realistic" performance of GSC in ISS orbits.

This paper discusses the latest progress in the development of GRAPE (Gamma-Ray Polarimeter Experiment), a hard X-ray Compton Polarimeter. The purpose of GRAPE is to measure the polarization of hard X-rays in the 50-300 keV energy range. We are particularly interested in X-rays that are emitted from solar flares and gamma-ray bursts (GRBs). Accurately measuring the polarization of the emitted radiation from these sources will lead, to a better understating of both the emission mechanisms and source geometries. The GRAPE design consists of an array of plastic scintillators surrounding a central high-Z crystal scintillator. We can monitor individual Compton scatters that occur in the plastics and determine whether the photon is photo absorbed by the high-Z crystal or not. A Compton scattered photon that is immediately photo absorbed by the high-Z crystal constitutes a valid event. These valid events provide us with the interaction locations of each incident photon and ultimately produces a modulation pattern for the Compton scattering of the polarized radiation. Comparing with Monte Carlo simulations of a 100% polarized beam, the level of polarization of the measured beam can then be determined. The complete array is mounted on a flat-panel multi-anode photomultiplier tube (MAPMT) that can measure the deposited energies resulting from the photon interactions. The design of the detector allows for a large field-of-view, at the same time offering the ability to be close-packed with multiple modules in order to reduce deadspace. We plan to present in this paper the latest laboratory results obtained from GRAPE using partially polarized radiation sources.

Radiation induced phosphorescence of uv windows has the potential for generating crippling levels of background signal in space flight sensors. VUV fluorescence spectra have been obtained for three common window materials, and the phosphorescence decay curves have been recorded for a range of temperatures for two of the samples tested. We present this data and employ models used to fit the STIS background data to analyze the observed decay curves.

A computer model of an Extreme Ultraviolet (EUV) spectrometer based on a gas ionization chamber and on flight experience of the Optics Free Spectrometer (OFS previously flown), was built and tested with the SIMulation of IONs (SIMION) tools. Our goal in this work was to design an improved and simplified electron beam focusing system which fits the dimensions (D = 180 mm; L = 380 mm) available for installation of a new OFS instrument in our sounding rocket flights, and to lower the focusing potentials from the 5,000 V in the previous OFS computer model to about 300 V in the current model. The advanced EUV OFS employs a six-electrode electron beam focusing system with focusing potentials of up to 250 V and can focus photo-electrons in a spectral range of 5.0 - 50.0 nm. The spectral resolution may be optimized throughout the whole spectral range by switching to an appropriate set of focusing potentials resulting in a resolution of about 0.10 - 0.25 nm, which is comparable to or better than the spectral resolution of typical EUV grating spectrometers designed for spaceflight applications. Modeled focusing of photo-electrons at the detector's aperture permits an increase in both spectral resolution and Signal to Noise Ratio (SNR) compared to those obtained with the dual-electrode OFS prototypes flown previously. A comparison of measured OFS EUV spectra (sounding rocket flight of 2003/12/05) with the modeled spectra showed that an advanced OFS for studying solar dynamics in the EUV with high spectral and temporal resolution is indeed quite feasible.

Gamma ray bursts (GRBs) are the most energetic eruptions known in the Universe. Instruments such as Compton-GRO/BATSE and the GRB monitor on BeppoSAX have detected more than 2700 GRBs and, although observational confirmation is still required, it is now generally accepted that many of these bursts are associated with the collapse of rapidly spinning massive stars to form black holes. Consequently, since first generation stars are expected to be very massive, GRBs are likely to have occurred in significant numbers at early epochs. X-red is a space mission concept designed to detect these extremely high redshifted GRBs, in order to probe the nature of the first generation of stars and hence the time of reionisation of the early Universe. We demonstrate that the gamma and x-ray luminosities of typical GRBs render them detectable up to extremely high redshifts (z ~ 10to30), but that current missions such as HETES and SWIFT operate outside the observational range for detection of high redshift GRB afterglows. Therefore, to redress this, we present a complete mission design from teh science case to the mission architecture and payload, the latter comprising three instruments, namely wide field x-ray cameras to detect high redshift gamma-rays, an x-ray focussing telescope to determine accurate coordinates and extract spectra, and an infrared spectrograph to observe the high redshift optical afterglow. The mission is expected to detect and identify for the first time GRBs with z > 10, thereby providing constraints on properties of the first generation of stars and the history of the early Universe.

InFOCμS is a new generation balloon-borne hard X-ray telescope with focusing optics and spectroscopy in a collaboration between NASA's GSFC and Nagoya University. We had a successful 22.5-hour flight from Fort Sumner, NM on September 16-17, 2004. The InFOCμS hard X-ray telescope consists of a depth-graded platinum-carbon multilayer mirror and a CdZnTe detector, which is a pixellated solid-state device capable of imaging spectroscopy. In this paper, we present the performance of the InFOCμS CdZnTe detector. The detector is configured with a 12 × 12 segmented array of detector pixels. The pixels are 2 mm square, and are placed on 2.1 mm centers. The averaged energy resolution is 4.4 keV at 60 keV and its standard deviation is 0.36 keV over 128 pixels. It has a ²⁴¹Am tagged source to monitor the energy gain of each detector pixel during the flight. The gain was stable within a few percent during observations. The detector is also surrounded by a 3-cm thick CsI anti-coincidence shield to reduce background from particles and photons not incident along the mirror focal direction. Owing to the active shield, 97.3% of the background was rejected as vetoed events. The observed background rate is 2.9 × 10^-4 cts sec^-1 cm^-2 keV^-1 (20-50 keV). We achieved sensitivity as great as 5 × 10-6 cts sec^-1 cm^-2 keV^-1 with 8-hour observations (in 20-50 keV and three sigma detection) in this flight. We also present our plan for the future InFOCμS flights as well as their sensitivity we would expect.

The X-Ray Telescope (XRT) on board the Swift satellite is a sensitive imaging spectrometer utilizing a MAT-22 CCD at the Focal plane. The system was designed to operate the CCD at -100 °C +/- 1 °C for the duration of the mission. Due to a failure of the temperature control sub-system, the CCD operates under variable thermal conditions dictated by the view factor of the radiator- heatpipe sub-system to the Earth and sun. A temperature variation of up to 5° C is seen during a single orbit due to the satellite transition from sun light into eclipse and the full operational regime of the instrument ranges from temperatures of -75°C to -45°C due to the persistent heating/cooling effects of satellite orientation to the sun and earth. To maintain the highest quality data products possible from the XRT data stream, a recalibration of the XRT is required to account for this variable thermal environment. We present the methodology for and results from a temperature dependent analysis of on-orbit XRT data, collected during the Swift commissioning phase, used to produce gain, bias and warm pixel calibration products. We also discuss the quality of XRT science products capable with these temperature dependent calibration files and future plans for updates to these calibration products.

SciSim is a complete simulator for the XMM-Newton X-ray observatory. Its purpose is to generate realistic simulated science data for a wide range of observational scenarios. SciSim is comprised of a number of separate simulators for the various components of the telescope and instruments on the XMM-Newton satellite. These act behind a Cosmic Simulator (CSIM), which allows the user to create source data, either through extracting sources from a catalogue, placing sources manually or simulating the sky. A ray generator (GSIM) generates data from the source for ray tracing, which is then fed down a pipeline formed by the spacecraft and instrument simulators. A fully configurable detailed physical description of all components, spacecraft, mirrors, gratings and CCD cameras, together with their interactions with X-rays, provide the means to perform deep simulation studies. The output of the simulations can be converted into a format compatible with the XMM-Newton Science Analysis System, and thus may be reduced in an identical manner to a real sky observation. The aim of the system is multiple: to develop observation strategies, to understand calibration effects and eventual aging / malfunction of the different components, to optimize analysis tools and algorithms and as an astrometry aided tool, that can be used during mission planning phases.

We present preliminary results on the operation of a Rockwell CMOS Hybrid imager as a soft X-ray imaging spectrometer. The CMOS Hybrid technology provides several significant advantages over conventional CCDs for high-energy astrophysics applications, and may be a viable alternative for future missions. The Rockwell Hybrid Visible Silicon (HyViSI^TM) imager consists of a thin slab of high-resistivity silicon which is flip-chip bonded using indium bumps to a Rockwell PICNIC CMOS multiplexer. Unlike more common CMOS imagers, the flip-chip bonding of the HYVISI provides 100% fill factor. The high-resistivity silicon provides high QE over the soft X-ray bandpass, while the multiplexer provides high level electronic integration. The detector has an amplifier per pixel, and various readout modes. The readout modes include the possibility of selecting arbitrary regions of interest and Fowler sampling to decrease noise and improve energy performance. We report on read noise, QE, and energy resolution, and on the effectiveness of multiple reads for noise reduction. We discuss future directions for this very promising technology which would make it ideal for use as an astronomical imaging spectrometer in the soft X-ray band.

This paper describes the design and operation of a low noise analogue readout system for X-ray CCDs (at up-to 1MHz pixel rate) for e2v's CCDs. A major part of the system is Correlated Double Sampler (CDS) Application Specific Integrated Circuit (ASIC) designed in collaboration with the CCLRC. Here we discuss the ASIC specification, design and applications, together with the measured performance.