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The performance of the PAW instrumentation on the 60kg Beagle 2 lander for ESA’s 2003 Mars Express mission will be described. Beagle 2 will search for organic material on and below the surface of Mars in addition to a study of the inorganic chemistry and mineralogy of the landing site. The lander will utilize acquisition and preparation tools to obtain samples from below the surface, and both under and inside rocks. In situ analysis will include examination of samples with an optical microscope, Mossbauer and fluorescent X-ray spectrometers. Extracted samples will be returned to the lander for analysis, in particular a search for organics and a measurement of their isotopic composition. The PAW experiment performance data will be described along with the status of the project.

Two rhesus monkeys were implanted with silicon arrays of 96 microelectrodes. Neural activity was recorded periodically over a period of weeks to months. We have developed a method to determine whether single units in two separate recording sessions represent the same neuron. Pairwise cross-correlograms, the autocorrelogram, waveform shape, and mean firing rate were used together as identifying features of a neuron. When two units recorded on separate days were compared using these features, their similarity scores tended to be either high, indicating two recordings from the same neuron, or low, indicating different neurons. Although these metrics are individually weak, together they produce a strong classifier. Some neurons were recorded for >100 days. These monkeys performed a center-out reaching task, and we found that the firing properties of chronically recorded neurons were stable over time.

Transition edge sensors (TESs) are high-sensitivity thermometers used in cryogenic microcalorimeters which exploit the steep gradient in resistivity with temperature during the superconducting phase transition. Practical TES devices tend to exhibit a white noise of uncertain origin, arising inside the device. We discuss two candidate models for this excess noise, phase slip shot noise (PSSN) and percolation noise. We extend the existing PSSN model to include a magnetic field dependence and derive a basic analytical model for percolation noise. We compare the predicted functional forms of the noise current vs. resistivity curves of both models with experimental data and provide a set of equations for both models to facilitate future experimental efforts to clearly identify the source of excess noise.

The Beagle 2 X-ray Spectrometer (B2 XRS) instrument was part of the Beagle 2 Mars lander payload and intended to perform in situ geochemical analyses of geological materials on Mars. The analytical performance of a spare version of the B2 XRS was compared with (1) a portable X-ray fluorescence (PXRF) spectrometer designed to perform terrestrial fieldwork and (2) a laboratory-based wavelength-dispersive (WD-XRF) system used to produce high quality geochemical data. The criteria used to assess the performance were based on fitting precision, accuracy and detection limit, determined from the analysis of international geochemical reference materials. The fitting precision of the B2 XRS and PXRF was found to be in agreement with the Horwitz function (a benchmark relating the analysed concentration of an analyte to its uncertainty) over 4 orders of magnitude of concentration range from 10-1 to 10-5 g/g. The PXRF generally had a better fitting precision than the B2 XRS because of its better resolution. In order of improving accuracy, the spectrometers generally are ranked B2 XRS, PXRF and WD-XRF for various major and trace elements. A limiting factor in the accuracy of the B2 XRS was the application of the algorithm used for its quantitative analysis. The detection limits for the spectrometers ranked in the same order as the accuracy as a result of improving signal-to-noise ratio (SNR) of elemental peaks, which is a direct consequence of improving resolution between these spectrometers. Overall, the B2 XRS was found to have a favourable analytical performance compared to the benchmark spectrometers, despite having met considerable design constraints and qualification tests as a planetary instrument.

Laboratory measurements are presented to study the effects of the physical properties of regolith on planetary soft X-ray fluorescence spectroscopy. Two laboratory setups are used to independently measure these regolith effects using lunar regolith analog samples with three different particle-size ranges. Discussion is given on the data analysis. Some of the data may be valid only for qualitative conclusions. Analytical modelling is used to separate the effects expected for a plane-parallel and homogeneous medium from those of measured regolith analogs. The surface roughness and porosity of the regolith are observed to induce an enhancement of the higher-energy part of the spectrum as a function of the incidence angle. The enhancement is larger for rougher surfaces. A brief discussion is given on the relevance of this study for future planetary missions carrying soft X-ray spectrometers.

Efforts to study the neural correlates of learning are hampered by the size of the network in which learning occurs. To understand the importance of learning-related changes in a network of neurons, it is necessary to understand how the network acts as a whole to generate behavior. Here we introduce a paradigm in which the output of a cortical network can be perturbed directly and the neural basis of the compensatory changes studied in detail. Using a brain-computer interface, dozens of simultaneously recorded neurons in the motor cortex of awake, behaving monkeys are used to control the movement of a cursor in a three-dimensional virtual-reality environment. This device creates a precise, well-defined mapping between the firing of the recorded neurons and an expressed behavior (cursor movement). In a series of experiments, we force the animal to relearn the association between neural firing and cursor movement in a subset of neurons and assess how the network changes to compensate. We find that changes in neural activity reflect not only an alteration of behavioral strategy but also the relative contributions of individual neurons to the population error signal.

We present a derivation of the mass of the graviton inside a superconductor or other quantum coherent matter, starting from the gravitomagnetic equations and using the breaking of U(1) phase rotational symmetry of particles with a macroscopic wavefunction. We arrive at a simple and complete analytical expression for the graviton mass in terms of fundamental constants, with the mass density of the superconductor the only free parameter entering the ratio of photon-to-graviton mass. We compare predictions of our graviton mass with existing experimental data concerning the Tate–Cooper pair mass anomaly [C.J. de Matos, M. Tajmar, Physica C: Superconductivity 432 (2005) 167; J. Tate, B. Cabrera, S.B. Felch, J.T. Anderson, Phys. Rev. Lett. 62 (1989) 845]. We then go on to show that the gravitomagnetic flux through a superconducting ring is quantised and the resulting gravitationally-induced currents are measurable in the laboratory, allowing experimental access to an effect of quantised gravitational flux. We also show that phase change effects in multiply connected superconductors are due to the sum of gravitomagnetic and magnetic flux penetrating the superconductor. Finally, we speculate on the possible relevance to neutron star core formation.

Many types of superconducting detectors naturally form Casimir cavities (Superconducting Tunnel Junctions, some Transition Edge Sensor geometries). We show that by influencing the energy balance of the superconducting-to-normal (S–N) transition of the cavity boundaries the Casimir effect can have an effect on the microscopic parameters of the detector, such as the superconducting energy gap and critical field. In order to determine whether these effects are practically important a rigorous mathematical discussion of the energy balance of the detector’s transition is required. We discuss the basis for such a rigorous analysis as well as the type of electromagnetism required and the inadequacy of existing Casimir effect solutions when applied to the superconducting system.

Modern microchannel plate detectors exhibit low quantum efficiency in the extreme ultra violet range compared to those manufactured before 1990. The cause of this reduction in efficiency is unknown. We describe recent investigations into the along-channel surface compositions of a number of microchannel plates (MCPs) of varying efficiency. These compositional profiles, generated using energy-dispersive X-ray spectroscopy, provide insight into possible mechanisms underlying the efficiency reduction and may assist in efforts to restore good extreme ultraviolet (EUV) performance to MCPs through modifications to the manufacturing process.

Recent and proposed future planetary missions are becoming increasingly concerned with detailed geochemical assessment, often in a bid to ascertain the presence of water and life supporting geochemical systems. The instruments involved may use some kind of radioactive source, e.g. X-ray fluorescence spectrometry, Mossbauer spectrometry, neutron scattering. Having radioactive sources on a lander/rover poses various potential problems, in regard to both safety to personnel involved in the building of the instrument and to radiation effects on spacecraft structure and on other instruments. Indeed background radiation effects from one instrument may dominate measurements in another resulting in loss of scientific performance. Drawing on experience with the Beagle 2 probe which contained two instruments with radioactive sources, we present a discussion on the management of radiation hazards and background effects posed by radioactive sources for such planetary missions.

We report on a new optimal filtering algorithm for improved energy and position resolution in position sensitive Transition Edge Sensor (TES) based X-ray detectors. This algorithm takes account of the noise correlation between the detector outputs to minimise the variance on the estimated photon energy and position. Using numerical methods we show that improved energy and position resolution can be obtained than from previously published methods. Our simulations also reveal the trade-offs resulting from changes in the thermal conductances and heat capacities of the detector elements.

The toroidal energy- and angle-resolved electron spectrometer (TEARES) is a state-of-the-art high-resolution electron detector, which measures both the energy and ejection angle of electrons simultaneously over a range of angles. A double-focussing cylindrical slit entrance lens transports and focusses electrons that are ejected near the plane perpendicular to the main axis of the spectrometer and which originate from an interaction volume of approximately 1 mm3 to the entrance of the toroidal analyser. In addition, the lens adjusts the kinetic energy of the electrons to be analysed to match the pass energy of the analyser with a relatively constant unit magnification. The toroidal deflector analyser is comprised of an inner and an outer toroidal sector, which disperses and focuses the electrons according to their energy in the radial dimension, it is defined by a spherical radius of 125 mm, a cylindrical radius of 120 mm and a sector angle of 142°. These dimensions have been chosen to ensure optimum focussing properties. A 1 mm high entrance slit provides an analyser resolution (ΔE/PE) of 0.0081 (=1/125). A single-focussing conical slit exit lens transports, demagnifies, focuses and accelerates the electrons from the exit of the analyser onto an imaging detector. Electrons travel through the spectrometer with their initial angular direction preserved. The whole of the spectrometer has no blind spots and incorporates a working distance defined by a 38–40 mm radius. The TEARES system is designed to operate over a kinetic energy range of

A fast imaging electron detector is being developed as part of the Toroidal Energy- and Angle-Resolved Electron Spectrometer (TEARES), a high-resolution electron spectrometer for use on synchrotron sources. The analysed solid angle of TEARES is about 100 times greater than that of a conventional hemispherical analyser of similar radius and entrance slit sizes. A ‘typical’ solid sample at a third-generation synchrotron source would yield count rates in excess of 1 GHz, >10 3 times the capability of available imaging electron detectors. We describe a prototype detector based on low-resistance microchannel plates and an adaptation of the cartesian two-dimensional CODACON encoder that aims to achieve a relatively modest 2 MHz counting rate with 32 by 128 simultaneous energy and angle channels. The encoder pattern has been optimised for the output electron distribution of TEARES and directly generates a binary address for each event using simple electronics and the minimum number of signal channels.

The high resolution gamma imager (HRGI): a CCD based camera for medical imaging. We describe the High Resolution Gamma Imager (HRGI): a Charge Coupled Device (CCD) based camera for imaging small volumes of radionuclide uptake in tissues. The HRGI is a collimated, scintillator-coated, low cost, high performance imager using low noise CCDs that will complement whole-body imaging Gamma Cameras in nuclear medicine. Using 59.5 keV radiation from a Am-241 source we have measured the spatial resolution and relative efficiency of test CCDs from E2V Technologies (formerly EEV Ltd.) coated with Gadox (Gd2O2S(Tb)) layers of varying thicknesses. The spatial resolution degrades from 0.44 to 0.6mm and the detection efficiency increases ( x 3) as the scintillator thickness increases from 100 to 500 mum. We also describe our first image using the clinically important isotope Tc-99m. The final HRGI will have intrinsic sub-mm spatial resolution (similar to 0.7 mm) and good energy resolution over the energy range 30-160 keV. (C) 2003 Elsevier B.V. All rights reserved.

We investigate, by ray-trace simulation, two hard X-ray telescopes based on microchannel plate (MCP) optics. The first is the, by now well known, lobster-eye geometry, while the second is a novel design. The second design uses a pair of MCPs with square channels packed in a radial fashion and represents a conical approximation to the Wolter type I configuration. We show that such telescopes can provide X-ray imaging at energies up to 100 keV. Effective area may be scaled arbitrarily by co-aligning many MCP optics. As an example, we calculate that 50 parallel Wolter I units each of 60 mm diameter and 5 m focal length yield a sensitivity of 1 milli Crab at 45 keV in a 105 second integration.

We report a high-resolution (R=3000-4000) spectroscopic observation of the DA white dwarf G191-B2B in the extreme ultraviolet band 220-245 A. A low- density ionised He component is clearly present along the line-of-sight, which if completely interstellar implies a He ionisation fraction considerably higher than is typical of the local interstellar medium. However, some of this material may be associated with circumstellar gas, which has been detected by analysis of the C IV absorption line doublet in an HST STIS spectrum. A stellar atmosphere model assuming a uniform element distribution yields a best fit to the data which includes a significant abundance of photospheric He. The 99-percent confidence contour for the fit parameters excludes solutions in which photospheric He is absent, but this result needs to be tested using models allowing abundance gradients., LATEX format: 10 pages and 3 figures: accepted for publication in the Astrophysical Journal Letters

We propose a novel imaging X-ray spectrometer to be flown on a space mission to a Near Earth Object (NEO) (the Moon, a near Earth asteroid or a comet). In either of the first two cases the instrument will record X-ray fluorescence excited from the surface by the solar X-ray flux to form “compositional maps” of its surface, providing valuable information on the evolution of these objects. In the case of a comet, the device will study the X-ray emission resulting from its interaction with the solar wind. During cruise when the spacecraft is en-route to the NEO the instrument will be used to make astronomical observations of Active Galactic Nuclei (AGN), X-ray binary stars and coronal sources in star clusters such as the Pleiades or Hyades. The instrument, proposed for ESA’s SMART-1 mission, is a miniature telescope, of 37.5 cm focal length, based on microchannel plate (MCP) optics and charged coupled device (CCD) detectors providing both imaging and a medium resolution ∼50–100 eV spectroscopic capability; sufficient to resolve the L lines of Ca, Ti, Fe, and the K lines of O, Mg, Al and Si with an angular resolution ∼10 arcmin and a 6×6° field of view.

We report on the experimental characterisation and modelling of Transition Edge Sensor (TES)-based Distributed Read-Out Imaging Devices (DROIDs), for use as position-sensitive detectors in X-ray astronomy. Latest experimental results from prototype DROIDs using Ir TESs with Au absorbers are reported. Through modelling and the development of signal processing algorithms we are able to design the DROID for optimum spectral and spatial resolution depending upon application.

We describe optimal filtering algorithms for determining energy and position resolution in position-sensitive Transition Edge Sensor (TES) Distributed Read-Out Imaging Devices (DROIDs). Improved algorithms, developed using a small-signal finite-element model, are based on least-squares minimisation of the total noise power in the correlated dual TES DROID. Through numerical simulations we show that significant improvements in energy and position resolution are theoretically possible over existing methods.

The Large Observatory For X-ray Timing (LOFT) is one of the candidate missions selected by the European Space Agency for an initial assessment phase in the Cosmic Vision programme. It is proposed for the M3 launch slot and has broad scientific goals related to fast timing of astrophysical X-ray sources. LOFT will carry the Large Area Detector (LAD), as one of the two core science instruments, necessary to achieve the challenging objectives of the project. LAD is a collimated detector working in the energy range 2-50 keV with an effective area of approximately 10 m^2 at 8 keV. The instrument comprises an array of modules located on deployable panels. Lead-glass microchannel plate (MCP) collimators are located in front of the large-area Silicon Drift Detectors (SDD) to reduce the background contamination from off-axis resolved point sources and from the diffuse X-ray background. The inner walls of the microchannel plate pores reflect grazing incidence X-ray photons with a probability that depends on energy. In this paper, we present a study performed with an ad-hoc simulator of the effects of this capillary reflectivity on the overall instrument performance. The reflectivity is derived from a limited set of laboratory measurements, used to constrain the model. The measurements were taken using a prototype collimator whose thickness is similar to that adopted in the current baseline design proposed for the LAD. We find that the experimentally measured level of reflectivity of the pore inner walls enhances the off-axis transmission at low energies, producing an almost flat-top response. The resulting background increase due to the diffuse cosmic X-ray emission and sources within the field of view does not degrade the instrument sensitivity., accepted for publication in Experimental Astronomy

We describe the X-ray properties of alkali halide photocathodes subjected to post-evaporation thermal treatments. Measurements made in St. Petersburg on planar CsI photocathodes, over an X-ray energy range 5–10 keV, show up to a five-fold increase in current quantum yield χ c (electrons/photon) after thermal annealing. Measurements were also made at Leicester on a microchannel plate (MCP) detector bearing thermally annealed CsI and KBr photocathodes. The MCP quantum efficiency Q (counts/photon) was measured, before and after annealing, at X-ray energies of 0.28, 1.74 and 2.56 keV. A small increase in quantum efficiency was observed at large angles of incidence for the annealed photocathodes. The heat-treated CsI coated MCP half also exhibited a much enhanced mean gain. Both planar photocathode and coated MCP measurements are interpreted with the aid of a semi-empirical photocathode model and scanning electron microscope (SEM) imagery.

We are investigating Transition-Edge Sensors (TESs) for future X-ray Astronomy missions. In this paper, we report the first X-ray results from a one-dimensional imaging spectrometer or Distributed Read-Out Imaging Device (DROID). The DROID consists of two Iridium TESs with transitions temperatures of ∼172 mK, at the ends of a 250 μm by 4.7 mm Gold absorber. The event position can be determined from pulse height and rise/fall time information. Initial results were obtained by reading one end of the DROID only.

The small mission A-STAR (All-Sky Transient Astrophysics Reporter) aims to locate the X-ray counterparts to ALIGO and other gravitational wave detector sources, to study the poorly-understood low luminosity gamma-ray bursts, and to find a wide variety of transient high-energy source types, A-STAR will survey the entire available sky twice per 24 hours. The payload consists of a coded mask instrument, Owl, operating in the novel low energy band 4-150 keV, and a sensitive wide-field focussing soft X-ray instrument, Lobster, working over 0.15-5 keV. A-STAR will trigger on ~100 GRBs/yr, rapidly distributing their locations., Comment: Accepted for the European Astronomical Society Publications Series: Proceedings of the Fall 2012 Gamma-Ray Burst Symposium held in Marbella, Spain, 8-12 Oct 2012

The Scientific objectives of the LOFT mission, e.g., the study of the Neutron Star equation of state and of the Strong Gravity, require accurate energy, time and flux calibration for the 500k channels of the SDD detectors, as well as the knowledge of the detector dead-time and of the detector response with respect to the incident angle of the photons. We report here the evaluations made to asses the calibration issues for the LAD instrument. The strategies for both ground and on-board calibrations, including astrophysical observations, show that the goals are achievable within the current technologies., Comment: Proceedings of SPIE, Vol. 8443, Paper No. 8443-208, 2012

We report on our activities, currently in progress, aimed at performing accelerator experiments with soft protons and hyper-velocity dust particles. They include tests of different types of X-ray detectors and related components (such as filters) and measurements of scattering of soft protons and hyper-velocity dust particles off X-ray mirror shells. These activities have been identified as a goal in the context of a number of ongoing space projects in order to assess the risk posed by environmental radiation and dust and qualify the adopted instrumentation with respect to possible damage or performance degradation. In this paper we focus on tests for the Silicon Drift Detectors (SDDs) used aboard the LOFT space mission. We use the Van de Graaff accelerators at the University of T\"ubingen and at the Max Planck Institute for Nuclear Physics (MPIK) in Heidelberg, for soft proton and hyper-velocity dust tests respectively. We present the experimental set-up adopted to perform the tests, status of the activities and some very preliminary results achieved at present time., Comment: Proceedings of SPIE, Vol. 8443, Paper No. 8443-24, 2012

The Extreme Physics Explorer (EPE) is a concept timing/spectroscopy mission that would use micro-channel plate optics (MCPO) to provide 4 square meters effective area focused to ~1 arc-min onto an X-ray calorimeter. We describe science drivers for such a mission, possible designs for the large area MCPO needed for EPE, and the challenges of the large area MCPO design., Comment: 12 pages, 9 figures, to appear in proceedings of SPIE V8147, "Optics for EUV, X-ray, and Gamma-Ray Astronomy V"

The Wide Field Imager (WFI) of the International X-ray Observatory (IXO) is an X-ray imaging spectrometer based on a large monolithic DePFET (Depleted P-channel Field Effect Transistor) Active Pixel Sensor. Filling an area of 10 x 10 cm2 with a format of 1024 x 1024 pixels it will cover a field of view of 18 arcmin. The pixel size of 100 x 100 μm2 corresponds to a fivefold oversampling of the telescope's expected 5 arcsec point spread function. The WFI's basic DePFET structure combines the functionalities of sensor and integrated amplifier with nearly Fano-limited energy resolution and high efficiency from 100 eV to 15 keV. The development of dedicated control and amplifier ASICs allows for high frame rates up to 1 kHz and flexible readout modes. Results obtained with representative prototypes with a format of 256 x 256 pixels are presented.

The Stellar X-ray Polarimeter (SXRP) is a focal plane instrument which will be flown on the SPECTRUM-X-Gamma mission in 1993. The polarimeter is composed of two separate instruments: the first exploits the dependence on the polarization of the Bragg reflection from a graphite crystal, and of the Thomson scattering from a metallic lithium target. The second instrument makes use of the recently discovered polarization dependence of X-ray photoemission from CsI. The SXRP will permit sensitive measurements of several classes of galactic X-ray sources, such as X-ray pulsars, black-hole candidates and supernova remnants. Moreover, and for the first time, SXRP will be able to perform highly sensitive measurements of the brightest extragalactic sources.

Two rhesus monkeys were trained to move a cursor using neural activity recorded with silicon arrays of 96 microelectrodes implanted in the primary motor cortex. We have developed a method to extract movement information from the recorded single and multi-unit activity in the absence of spike sorting. By setting a single threshold across all channels and fitting the resultant events with a spline tuning function, a control signal was extracted from this population using a Bayesian particle-filter extraction algorithm. The animals achieved high-quality control comparable to the performance of decoding schemes based on sorted spikes. Our results suggest that even the simplest signal processing is sufficient for high-quality neuroprosthetic control.

As part of a comprehensive study of X-ray emission from planetary surfaces and in particular the planet Mercury, we have measured fluorescent radiation from a number of planetary analog rock samples using monochromatized synchrotron radiation provided by the BESSY II electron storage ring. The experiments were carried out using a purpose built X-ray fluorescence (XRF) spectrometer chamber developed by the Physikalisch-Technische Bundesanstalt, Germany’s national metrology institute. The XRF instrumentation is absolutely calibrated and allows for reference-free quantitation of rock sample composition, taking into account secondary photon- and electron-induced enhancement effects. The fluorescence data, in turn, have been used to validate a planetary fluorescence simulation tool based on the GEANT4 transport code. This simulation can be used as a mission analysis tool to predict the time-dependent orbital XRF spectral distributions from planetary surfaces throughout the mapping phase.

X-ray emission from charge exchange recombination between the highly ionized solar wind and neutral material i n Earth's magnetosheath has complicated x-ray observations of celestial objects with x-ray observatories including ROSAT, Chandra, XMM-Newton, and Suzaku. However, the charge-exchange emission can also be used as an important diagnostic of the solar-wind interacting with the magnetosheath. Soft x-ray observations from low-earth orbit or even the highly eccentric orbits of Chandra and XMM-Newton are likely superpositions of the celestial object of interest, the true extra-solar soft x-ray background, geospheric charge exchange, and heliospheric charge exchange. We show that with a small x-ray telescope placed either on the moon, in a similar vein as the Apollo ALSOP instruments, or at a stable orbit near L1, we can begin t o disentangle the complicated emission structure in the soft x-ray band. Here we present initial results of a feasibility study recently funded by NASA t o place a small x-ray telescope on the lunar surface. The telescope operates during lunar night to observe charge exchange interactions between the solar wind and magnetospheric neutrals, between the solar wind and the lunar atmosphere, and an unobstructed view of the soft x-ray background without the geospheric component.

Trigeminal ganglion neurons in adult rats adapt to periodic whisker deflections in the range of 1-40 Hz, manifested as a reduction in spike counts to progressively later stimuli in a train of pulsatile or sinusoidal deflections. For high velocity, pulsatile deflections, adaptation is time- and frequency-dependent; as in the case of thalamic and cortical neurons, adaptation is greater at higher stimulus frequencies. With slower velocity, sinusoidal movements, trigeminal ganglion cells differ from central neurons, however, by exhibiting strong adaptation even at low frequencies. For both types of stimuli, effects in trigeminal ganglion neurons were more pronounced in rats maintained during the recording session under neuromuscular blockade than in non-paralysed animals. Results are consistent with previous findings in other systems that frequency-dependent adaptation of cutaneous primary afferent neurons is affected by mechanical properties of the skin. Such effects are likely to vary depending on the nature of the whisker stimuli and physiological states that affect skin viscoelasticity.

In order to keep up with the large improvements in synchrotron radiation, we have developed a toroidal‐based electron spectrometer capable of collecting electrons emitted over a large angular range, whilst preserving emission direction information. This system has an analyser defined by spherical radius of 125 mm, cylindrical radius of 120 mm, sector angle of 142°, and useable azimuthal angle of ∼230°. A 1 mm high analyser entrance slit provides a theoretical analyser resolution (ΔE/PE) of 0.0081. The spectrometer has no blind spots and incorporates a working distance defined by a ∼40 mm radius. It operates over the kinetic energy range

APEX is a proposed mission for a Small Explorer (SMEX) satellite. APEX will investigate the density, temperature, composition, magnetic field, structure, and dynamics of hot astrophysical plasmas (log T = ~5-7), which emit the bulk of their radiation at EUV wavelengths and produce critical spectral diagnostics not found at other wavelengths. APEX addresses basic questions of stellar evolution and galactic structure through high-resolution spectroscopy of white dwarf stars, cataclysmic variables, the local interstellar medium, and stellar coronae. Thus APEX complements the Chandra , Newton-XMM , FUSE , and CHIPS missions. The instrument is a suite of 8 near-normal incidence spectrometers (~90-275 Angstroms, resolving power ~10,000, effective area 30-50 cm 2 ) each of which employs a multilayer-coated ion-etched blazed diffraction grating and a microchannel plate detector of high quantum efficiency and high spatial resolution. The instrument is mounted on a 3-axis stabilized commercial spacecraft bus with a precision pointing system. The spacecraft is launched by a Taurus vehicle, and payload size and weight fit comfortably within limits for the 2210 fairing. Of order 100 targets will be observed over the baseline mission of 2 years. These are selected carefully to maximize scientific return, and all were detected in the EUVE and the ROSAT WFC surveys.

We describe the design of Lobster-ISS, an X-ray imaging all-sky monitor (ASM) to be flown as an attached payload on the International Space Station. Lobster-ISS is the subject of an ESA Phase-A study which will begin in December 2001. With an instantaneous field of view 162 x 22.5 degrees, Lobster-ISS will map almost the complete sky every 90 minute ISS orbit, generating a confusion-limited catalogue of ~250,000 sources every 2 months. Lobster-ISS will use focusing microchannel plate optics and imaging gas proportional micro-well detectors; work is currently underway to improve the MCP optics and to develop proportional counter windows with enhanced transmission and negligible rates of gas leakage, thus improving instrument throughput and reducing mass. Lobster-ISS provides an order of magnitude improvement in the sensitivity of X-ray ASMs, and will, for the first time, provide continuous monitoring of the sky in the soft X-ray region (0.1-3.5 keV). Lobster-ISS provides long term monitoring of all classes of variable X-ray source, and an essential alert facility, with rapid detection of transient X-ray sources such as Gamma-Ray Burst afterglows being relayed to contemporary pointed X-ray observatories. The mission, with a nominal lifetime of 3 years, is scheduled for launch on the Shuttle c.2009.

We describe HERMES (High Energy Remote-Sensing of Mercury's Surface), a novel X-ray imaging spectrometer for potential accommodation in the Mercury Planetary Orbiter (MPO) component of ESA's BepiColombo mission to Mercury. The instrument combines recently developed micro channel plate optics with large-format compound semiconductor imaging arrays. MCP optics offer the distinct advantage of a large collecting area coupled to arcminute angular resolution in a light-weight package and short focal length. Measurements on a prototype optic indicate it should be possible to achieve an angular resolution below 1 arcmin over a fov of 1 degree(s). Energy resolution of 270 eV FWHM at 5.9 keV has been achieved at room temperature for a prototype GaAs array. We estimate that HERMES will detect ~2000 x-ray fluorescent photons s-1 from the surface of Mercury during solar quiet conditions at the pericenter of the orbit. The maximum expected surface spatial resolution from this altitude is ~200m and the fov 40 km2. Over the orbiter's 2 year mission life, HERMES will provide the first very high resolution compositional maps of any planetary surface.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We have fabricated the four flight gratings for a sounding rocket high-resolution spectrometer using a holographic ion-etching technique. The gratings are spherical (4000-mm radius of curvature), large (160 mm x 90 mm), and have a laminar groove profile of high density (3600 grooves/mm). They have been coated with a high-reflectance multilayer of Mo5C/Si/Mo2Si. Using an atomic force microscope, we examined the surface characteristics before and after multilayer coating. The average roughness is approximately 2-3A rms after coating, somewhat smoothened by the multilayer. Using synchrotron radiation, we completed an efficiency calibration map of each grating over the wavelength range 225-245A. At an angle of incidence of 5 degree(s) and a wavelength of 234A, the average efficiency peaks in the first inside order at 10.3+/- 0.6% for Grating 1, 7.3+/- 0.9% for Grating 6, 7.2+/- 1.2% for Grating 3, and 9.0+/- 1.5% for Grating 4. These values exceed all previously published results for a high density grating. The first order groove efficiency for Grating 1 is 34.4+/- 1.9%, in good agreement with the best value obtained from similar test gratings and close to the theoretical limit of 40.5%.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.