The gamma-ray large area space telescope (GLAST) mission is planned as the next major challenge in high-energy astrophysics. FiberGLAST is one of the technologies being developed for GLAST and is using arrays of scintillation fibers for the pair-tracking and calorimeter detectors. The instrument requires optical detectors with high gain, low cost, and low power to read out the large number of individual fibers.

FiberGLAST is a scintillating fiber gamma-ray detector designed for the GLAST mission. The system described below provides superior effective area and field of view for modest cost and risk. An overview of the FiberGLAST instrument is presented, as well as a more detailed description of the principle elements of the primary detector volume. The triggering and readout electronics are described, and Monte Carlo Simulations of the instrument performance are presented.

The FiberGLAST scintillating fiber telescope is a large-area instrument concept for NASA's GLAST program. The detector is designed for high-energy gamma-ray astronomy, and uses plastic scintillating fibers to combine a photon pair tracking telescope and a calorimeter into a single instrument. A small prototype detector has been tested with high energy photons at the Thomas Jefferson National Accelerator Facility. We report on the result of this beam test, including scintillating fiber performance, photon track reconstruction, angular resolution, and detector efficiency.

IBIS is the imaging telescope onboard the ESA satellite INTEGRAL, which will be launched in September, 2001. IBIS will produce images of the gamma-ray sky in the region between 15 keV and 10 MeV by means of a position sensitive detection lane coupled with a coded aperture mask. The detection plane of IBIS comprises two position sensitive layers: ISGRI and PICsIT. PICsIT is a 64 X 64 unit array of approximately equals 0.75 cm² crystals operative in the energy range between 150 keV and 10 MeV. The engineering model (EM) of PICsIT has now been calibrated and delivered to ESA. In this work we present the preliminary results obtained from the PICsIT EM scientific calibrations. These test were the first occasion for measuring the general behavior of the detector in terms of the key scientific performances. The gain, linearity, energy resolution, lower energy threshold and background counting rate for each detection unit and the variation of these parameters as a function of pixel position and were measured. Preliminary results regarding event multiplicity distribution, and energy resolution degradation for multiple events are also presented.

IBIS is the high energy imagin telescope onboard the ESA satellite INTEGRAL, which will be launched in September 2001. The detection p;lane of IBIS comprises two position sensitive layers: ISGRI and PICsIT. PICsIT consists of a 64 X 64 unit array of approximately equals 0.8 cm² crystals operating in the energy range between 150 keV and 10 MeV. Due to the low intrinsic signal-to-noise ratio of the cosmic sources in the gamma-ray domain, INTEGRAL observing times will be very long, lasting about 10⁵-10⁶ s. Moreover, the image formation principle on which PICsIT works is that of coded aperture imaging in which the entire detection plane contributes to each decoded sky pixel. For these two reasons, the spatial and temporal uniformity in gain, linearity and energy resolution of the individual detection units is of paramount importance for fully exploiting the capabilities of the instrument. In IBIS this is accomplished by having onboard a low-intensity tagged radioactive source constantly illuminating the entire detection plane with 511 and 1275 keV energy photons. Herein we describe the scientific rationale and requirements of the in-flight calibration system from the point of view of the high energy detector PICsIT, and the impact on the PICsIT scientific performance as a function of the overall calibration accuracy achieved during the flight.

The Constellation-X mission is a large collecting area x-ray facility, emphasizing observations at high spectral resolution while covering a broad energy band. By increasing the telescope aperture and utilizing efficient spectrometers the mission will achieve a factor of 100 increased sensitivity over current high resolution x-ray spectroscopy missions. The use of focusing optics across the 10-40 keV band will provide a similar factor of 100 increased sensitivity in this band. Key technologies under development for the mission include lightweight high throughput x-ray optics, multilayer coatings to enhance the hard x-ray performance of x-ray optics, micro-calorimeter spectrometer arrays with 2 eV resolution, low power and low weight CCD arrays, lightweight gratings and hard x-ray detectors. When observations commence towards the end of the next decade, Constellation-X will address many pressing questions concerning the extremes of gravity and the evolution of the Universe.

The Constellation-X Spectroscopy X-ray Telescope (SXT) will provide high-throughput, high-resolution spectroscopy of cosmic sources, form 0.25 keV to 10 keV. Key to this capability is the development of large, lightweight optics for the SXT mirror assembly. Teams led by NASA's Marshall Space Flight Center (MSFC), by NASA's Goddard Space Flight Center (GSFC), and by Italy's Osservatorio Astronomico di Brera are currently developing competing mirror technologies for this planned mission. Each team is making significant research progress in developing mirror technologies which satisfy the SXT requirements for lightweight optics, consistent with a system-level optical performance of better than 15 arcsec half-power diameter. The NASA MSFC, in collaboration with the Smithsonian Astrophysical Observatory, has focused its efforts on full-shell replicated optics, of electroformed nickel alloys. Recent progress in identifying a surface treatment to effect low, controlled adhesion and, more significantly, in developing new high-strength nickel alloys make this a viable, low-cost approach to satisfying the SXT requirements.

COnstellation-X is a cluster of identical observatories that together constitute a promising concept for a next- generation, high-throughput, high-resolution, astrophysical x-ray spectroscopy mission. The heart of the Constellation-X mission concept is a high-quantum-efficiency imaging spectrometer with 2 eV resolution at 6 keV. Collectively across the cluster, this imaging spectrometer will have twenty times the collecting efficiency of XRS on Astro-E and better than 0.25 arc minute imaging resolution. The spectrometer on each satellite will be able to handle count rates of up to 1000 counts per second per imaging pixel for a point source and 30 counts per second per pixel for an extended source filling the array. Focal plane coverage of at least 2.5 arc minutes X arc minutes, comparable to XRS but with a factor of thirty more pixels, is required. This paper will present the technologies that have the potential to meet al these requirements. It will identify the ones chosen for development for Constellation-X and explain why those were considered closer to realization, and it will summarize the results of the development work thus far.

The optical chain of the spectroscopic x-ray telescopes aboard the Constellation-X spacecraft employs a reflective grating spectrometer to provide high resolution spectra for multiple spectra as a slitless spectrometer in the spectral feature rich, soft x-ray band. As a part of the spectroscopic readout array, we provide a zero-order camera that images the sky in the soft band inaccessible to the microcalorimeters. Technological enhancements required for producing the RGS instruments are described, along with prototype development progress, fabrication and testing results.

In addition to high resolving power in the traditional x-ray band, the Constellation X-ray scientific goals require broad bandpass, with response extending to E >= 40 keV. To achieve this objective, Constellation-X will incorporate a hard x-ray telescope (HXT) based on depth graded multilayer- coated grazing incidence optics and position-sensitive solid state detectors. This paper describes the HXT performance requires, provides an overview of the HXT optics and detector technology development efforts, and present example designs.

The Astro-E High Resolution X-ray Spectrometer (XRS) was developed jointly by the NASA/Goddard Space Flight Center and the Institute of Space and Astronomical Science in Japan. The instrument is based on a new approach to spectroscopy, the x-ray microcalorimeter. This device senses the energies of individual x-ray photons as heat with extreme precision. A 32 channel array of microcalorimeters is being employed, each with an energy resolution of about 12 eV at 6 keV. This will provide spectral resolving power 10 times higher than any other non-dispersive x-ray spectrometer. The instrument incorporates a three stage cooling system capable of operating the array at 60 mK for about two years in orbit. The array sits at the focus of a grazing incidence conical mirror. The quantum efficiency of the microcalorimeters and the reflectivity of the x-ray mirror system combine to give high throughput over the 0.3- 12 keV energy band. This new capability will enable the study of a wide range of high-energy astrophysical sources with unprecedented spectral sensitivity. This paper presents the basic design requirements and implementation of the XRS, and also describes the instrument parameters and performance.

The XRS instrument has an array of 32 micro-calorimeters at the focal plane. These calorimeters consist of ion-implanted silicon thermistors and HgTe thermalizing x-ray absorbers. These devices have demonstrated a resolution of 9 eV at 3 keV and 11 eV at 6 keV. We will discuss the basic physical parameters of this array, including the array layout, thermal conductance of the link to the heat sink, operating temperature, thermistor size, absorber choice, and means of attaching the absorber to the thermistor bearing element. We will present representative performance data, though a more detailed presentation of the results of the instrument calibration is presented elsewhere in these proceedings. A silicon ionization detector is located behind the calorimeter array and serves to reject events due to cosmic rays. We will briefly describe this anti-coincidence detector and its performance in conjunction with the array.

XRS is the microcalorimeter x-ray detector aboard the US- Japanese ASTRO-E observatory, which is scheduled to be launched in early 2000. XRS is a high resolution spectrometer - with less than 9 eV resolution at 3 keV and better than 14 eV resolution over its bandpass ranging from about 0.3 keV to 15 keV. Here we present the results of our first calibration of the XRS instrument. We describe the methods used to extract detailed information about the detection efficiency and spectral redistribution of the instrument. We also present comparisons of simulations and real data to test our detector models.

The Hard X-ray Detector (HXD) is one of the three instruments on the fifth Japanese cosmic X-ray satellite ASTRO-E, scheduled for launch in January 2000. The HXD covers a wide energy range of 10-600 keV, using 16 identical GSO/BGO phoswich-counter modules, of which the low-energy efficiency is greatly improved by adding 2 m-thick silicon PIN diodes. Production of the HXD has been completed and pre-flight calibration is now in progress. The design concept of the HXD sensor, detail of the production process, and a brief summary of the measured performance is reported.

We introduce a new method of event analysis with the x-ray CCD camera (XIS) on board the next Japanese X-ray astronomical satellite, Astro-E. In the ordinary method, we used 'grade' classification; we distinguished the x-ray events from background events by referring the shape and the extent of the charge-split pixels, because non x-ray events spread to many pixels. However, at the same time, this method lowered the quantum efficiency of high energy x-ray photons which also extend for several pixels. We tried the method with 2D image-fitting of each event. We succeeded in rejecting non x-ray events by the extent of fitted function. We achieved higher detection efficiency by 10 percent than the grade method for hard x-rays above 8 keV, while the energy resolution becomes worse by 0-8 percent. The improvements and the problems of this new method are also presented.

ABRIXAS is a small German satellite project having the goal of surveying the sky in the x-ray band between 0.5 and 12 keV, thereby extending the former ROSAT all-sky survey towards higher energies. It consists of seven highly nested Wolter-I mirror systems which share one common focal plane camera, a CCD detector of the novel pn-type. ABRIXAS benefits from previously developed technologies or existing instruments. ABRIXAS was launched successfully into a low earth orbit by a Russian KOSMOS rocket in late April 1999. A few hours after its launch, however, the mission failed due to a battery problem. Currently, a repetition of the mission is under discussion because both the scientific goal and the mission concept are still be regarded as very attractive.

The pn-Charge Coupled Device (pn-CCD) camera was developed as one of the focal plane instruments for the European Photon Imaging Camera on board the x-ray multi mirror mission. An identical camera was foreseen on board ABRIXAS, a German x-ray satellite. The pn-CCD camera is an imaging x- ray detector for single photon counting, operating at a temperature below -80 degrees C. Due to a 0.3 mm depletion depth of the CCDs, the detector has a high quantum efficiency up to 15 keV. The effective area of the instrument is 6 cm X 6 cm with 12 CCDs monolithically integrated on a single silicon wafer. The camera includes a filter wheel with different filters for suppression of optical and UV light. A radioactive source provides an in- orbit calibration. In this paper we give an overview of the mechanical, thermal and electrical design of the instrument and a description of different readout and test modes. More detailed information about the performance and calibration of the instrument can be found in companion papers.

A 6 cm X 6 cm large monolithic charge coupled device has been developed and fabricated as focal plane x-ray detector for the European XMM satellite mission and the German ABRIXAS mission. This spectroscopic silicon detector is denominated pn-CCD because of its use of reverse biased pn- junctions as charge transfer registers, as ultra-thin homogeneous photon entrance window and for the on-chip electronics. Due tot he pn-CCD concept, the whole wafer thickness of 300 micrometers is sensitive to ionizing radiation. The read-out is performed in parallel and needs only 73 ms for the 36 cm² large detector area. A uniform low noise performance is realized by on-chip integrated JFET electronics. The two best pn-CCDs have been integrated in the flight cameras for XMM and abrixas and extensively tested for the long term operation in space. The presentation comprises the basic concept of the detector, a short description of the flight device and its fabrication, test and operating as well as the key performance parameters. The concluding outlook describes methods of further development of the pn-CCD.

The pn-CCD camera is developed as one of the focal plane instrument for the European Photon Imaging Camera (EPIC) on board the x-ray multi mirror mission (XMM) to be launched in December 1999. On 28 April 1999 an almost identical camera was launched on the German x-ray satellite ABRIXAS. The detector consists of four quadrants of three pn-CCDs each, which are integrated on a single silicon wafer. Each CCD has 200 X 64 pixels with 280 micrometers depletion depth, resulting in good quantum efficiency up to 15 keV. To minimize photon pile-up and/or image smearing by out-of-time events, six standard readout modes with integration times ranging from 7 microsecond(s) ec up to 280 msec can be selected by the observer. Background and noise reduction is achieved by means of on board generated offset maps and hard wired common mode filtering. Tracks of minimum ionizing particles are identified and suppressed by the experiment software on board. In this paper we give an overview of the on board event processing and describe important operation aspects of the pn-CCD camera.

In the near future the European x-ray satellite XMM will be launched into orbit. The satellite is equipped with a PN-CCD camera with a sensitive area of 60 mm X 60 mm, integrated on a single silicon wafer. The same camera is on board of the German x-ray satellite ABRIXAS. The main feature of this camera type is the very good quantum efficiency of more than 90 percent in the energy range from 0.3 to 10 keV and the high time resolution, selectable between 7 microsecond(s) ec and 280 msec. All flight cameras are extensively calibrated, utilizing the long beam test facility Panter in Muenchen, the Synchrotron Radiation Facility beam lines at the Institut d'Astrophysique Spatiale in Orsay, and the PTB beam line at the Bessy Synchrotron in Berlin. We will give an overview of all the calibrations and calibration methods as well as some global results.

A single-photon counting x-ray camera based on a fully depleted pn-CCD was developed by the Max-Planck-Institut fuer extraterrestrische Physik. It will be used on the european x-ray satellite XMM as one out of three focal plane detectors. The radiation hard device exhibits an intrinsic charge transfer loss due to titanium deep level trap contamination in the starting material. In order to realize the high spectral resolution of the device, the effects of charge transfer loss have to be corrected. The loss is a function of temperature, signal charge, clocking and the individual transfer history of a transfer channel. A model based on the capture and emission process of electron is in deep level traps has been developed and is applied to the charge transfer loss of the MPE pn-CCD x-ray camera. Each signal is corrected individually. The electron distribution within the potential well and the timing scheme is taken into account. The effect of charge generation due to thermally generated current and residual light proves to be an important parameter of the model. The model is in god agreement with the calibration data of the camera.

In CCDs part of the charge released by an absorbed photon is lost during transfer to the readout node. This loss depends on several parameters, in particular on the position where the photon was detected, its energy, the temperature of the CCD, and the saturation of traps by charges preceding along the readout direction. In order to determine how these parameters affect the charge loss of the pn-CCD cameras, we obtained extensive sets of calibration measurements form February 1998 to January 1999. More than three billion events were recorded in flatfield exposures. We present results of a detailed analysis of this data set and describe how they can be used to correct pn-CCD camera data for charge transfer loss.

We have provided optical filters developed at the Max-Planck Institut fuer extraterrestrische Physik to the German x-ray astronomy observatory ABRIXAS. Specific Si-PN CCDs will be serving as focal plane camera. Since this detector is sensitive to radiation from the x-ray to the near IR spectral range, for observation in x-ray astronomy it must be protected from visible and UV radiation. This is achieved by an optical filter which combines a high transmittance for photon energies in the soft x-ray range and a high transmittance for photon energies in the soft x-ray range and a high absorptance for UV and visible radiation. With respect to the mission goal in orbit a spectral transmittance function is required attenuating radiation below photon energies of 10 eV by more than 7 orders of magnitude and transmitting soft x-ray photon energies above 1000 eV by more than 90 percent. This was realized by a 0.80 micrometers thick polypropylene film coated with approximately 60 nm aluminum on both sides. The filter has an effective diameter of 73 mm without any support structure. Environmental test have been performed and proved the filters to be resistant against acoustic nose and vibrational load during the launch. Synchrotron radiation in the photon energy range from 60 eV to 2000 eV was used to characterize the spectral transmittance in the center and the transmittance topography across the filter. The thickness of the surface oxide layer was determined by x-ray reflectance measurements on an Al-layer in order to study longterm variations of transmittance caused by oxidation effects. We present the resulting performance data.

The European Photon Imaging Camera (EPIC) is one of the major Instruments on board the X-ray Multi-Mirror (XMM) mission planned for launch in January 2000. Ground calibrations have been performed in 1997 and 1998 on the flight and spare models of the MOS-CCD focal plane cameras at the Orsay Synchrotron Facility at IAS in France. The calibration data takings have been completed in December 1998. Details of the calibration equipment have already been presented elsewhere and at the SPIE Annual Meeting. This paper is an overview of the calibration activities and present the status and result of the calibration data analysis.

In the frame of XMM testing, all the mirror modules have been illuminated by a vertical EUV collimated beam a the Centre Spatial de Liege. A mirror module consists in 58 co- focal and co-axial Wolter I mirrors. Up to now the images obtained at CSL have been used to assess the Mirror Module optical performances in a flight representative configuration, and also to verify the impact of the thermal environmental and vibration test on the optical performance. Due to the highly complex design of the Mirror Modules, simulating XMM images in details is very difficult. The Point Spread Function of some of the mirror modules presents slight asymmetry. In the facility design study, it has been demonstrated that the diffraction impact at 58.4 nm is negligible with respect to the half energy width mirror module specification. Presently all the mirror modules are better than 165 arcsec. This paper presents first the diffraction contribution on the image. In a second step a point spread function is built by using the metrological mirror shell data. EUV images are then analyzed to evaluate the impact of the mirror interface structure integration process on the PSF. An analytical model of the measured EUV pSF is developed. The modelization technique is applied to simulate in-orbit image. Finally the different modelizations are evaluated and compared.

We present results from recent measurements of the channel stop structures in AXAF CCDs. We discuss refinements of a technique that uses a thin metal film with small, periodically spaced holes to restrict incident photons to well-defined regions of the pixel, providing a way to probe sub-pixel structure. By making monochromatic measurements at different energies, we can reliably determine the width and thickness of the channel stop p^PLU-type silicon implant and its insulating oxide layer.

A mesh experiment for the x-ray CCD enables us to specify the interaction position of the x-ray photon with subpixel resolution. There are two types of experiments: a single- pitch mesh experiment and a multi-pitch mesh experiment. Using the multipitch mesh experiment, we have established the method to measure the charge cloud shape inside the CCD produced by an x-ray photon. We can measure signal outputs from the pixel according to the interaction position of x- rays. Finally, we obtain, in detail, the charge cloud shape which can be well represented by an asymmetric Gaussian function. The symmetry of the charge cloud shape is probably due to the asymmetry of the electric field inside the CCD.

We have experimentally shown that heavily doped p⁺ layer at the silicon-silicon dioxide interface leads to charge losses in the signal electron clouds due to surface recombination and results in degraded energy resolution of the response of backside illuminated AXAF CCDs to low energy x-rays. The size of secondary ionization cloud generated by an incident x-ray photon can be much larger than that predicted from higher energy electron range-energy relations as the frontside illuminated CCD, while having high quantum efficiency at low energies. It shrinks the area of the heavily doped silicon to less than 2 percent of the pixel are, thus dramatically reducing recombination losses. If this design is combined with fully depleted silicon structures, it promises a highly efficiency x-ray sensor with a good energy resolution throughput the 0.1-15 keV band.

We have designed, built, and tested a low cost, flexible X- ray CCD camera for laboratory use to assist with the calibration of the Chandra x-ray Observatory High Resolution Camera (HRC). This CCD camera design will also serve as a prototype for future light opportunities. In this paper, we describe the design and performance of this camera, and present some sample data. For initial testing, we have purchased a commercially available EEV 30-11 CCD, but the camera can be modified to accommodate virtually any device in a minimal amount of time. We have achieved a readnoise of 3.5 electrons, and an energy resolution of 135 eV at Mn K(alpha) , with the EEV 30-11 device. This camera will be used extensively in the near future for HRC related calibrations.

The array of low energy x-ray imaging sensors (ALEXIS) satellite was launched from the 4th flight of the Pegasus booster on 25 April 1993 into an 800 km, 70 degree inclination orbit. After an initial launch difficulty, the satellite was successfully recovered and is still producing 100 MB of mission data per day. ALEXIS, still going strong in its sixth year, was originally designed to be a high risk, single string, Smaller-Faster-Cheaper satellite, with a 1-year nominal and a 3-year design limit. This paper will discuss the on-orbit detector performance including microchannel plate operation, pre- and post-flight calibration efforts, observed backgrounds and impacts of flying in a high radiation environment.

The ALEXIS mission, serving as the first dedicated all-sky monitor in the extreme UV (EUV), has been collecting data since its launch in 1993. ALEXIS operates in a 70 degree inclination orbit at an altitude of 800 km. The ALEXIS science mission is to observe the cosmic UV background and to study variability of EUV sources. The ALEXIS experiment is composed of six telescopes. Although ALEXIS was designed for a one-year technology verification mission, the telescopes are still functioning with much the same effectiveness as at the beginning of the mission. The telescopes comprise: 1) layered synthetic microstructure (LSM) spherical mirrors, 2) thin foil filters, and 3) microchannel plate detectors, all enshrouded within the telescope body. The LSM mirrors select the bandpass for each telescope, while providing enhanced rejection of the HeII 304 angstrom geocoronal radiation. The filters, constructed either form aluminum/carbon or Lexxan/titanium/boron, serve to strongly erect the geocoronal radiation, as well as longer wavelength emission from bright O or B stars. Each telescope detector consists of two plates, the outermost of which is curved to accurately match the spherical focal surface of the mirror. By reviewing the ground and flight histories, this paper analyzes the flight performance of the filters, including the effects of long term exposure and the formation of pinholes.

Two successful sounding rocket flights were launched on May 15, 1997 and November 2, 1998 with an objective of providing inter-calibration with several of the instruments on board SoHO and TRACE. We will discuss here the results of the inter-calibration between the SwRI/LASP rocket imaging instruments and the Extreme-UV Imaging Telescope (EIT) on SoHO. The MXUVI sounding rocket instrument is a multi-layer mirror telescope equipped with a special internal occulter and light trap to provide full disk imags of Fe IX/X 17.1 nm and off-limb observations of He II 30.4 nm. The SoHO/EIT instrument is also a full disk multi-layer imager with four channels, Fe IX/X 17.1 nm, FE XII 19.5 nm, Fe XV 28.4 nm and He II 30.4 nm. By comparison with the EIT observations taken at the same time we can quantify the sensitivity degradation of the EIT detector, as well as measure the off-limb stray- light characteristics of the two instruments.

DSRI has initiated a development program of CZT x-ray and gamma ray detectors employing strip readout techniques. A dramatic improvement of the energy response was found operating the detectors as so-called drift detectors. For the electronic readout, modern ASIC chips were investigated. Modular design and the low power electronics will make large area detectors using the drift strip method feasible. The performance of a prototype CZT system will be presented and discussed.

New, high spatial resolution CdZnTe (CZT) and silicon (Si) pixel detectors are highly suitable for x-ray astronomy. These detectors are planned for use in wide field of view, imaging x-ray, and low energy gamma-ray all-sky monitor (AXGAM) in a future space mission. The high stopping power of CZT detectors combined with low-noise front-end readout makes possible an order of magnitude improvement in spatial and energy resolution in x-ray detection. The AXGAM instrument will be built in the form of a fine coded aperture placed over two-dimensional, high spatial resolution and low energy threshold CZT pixel detector array. The preliminary result of CZT and silicon pixel detector test with low-noise readout electronics system are presented. These detectors may also be used with or without modification for medical and industrial imaging.

We report on the design and laboratory testing of a prototype imaging CZT detector intended for balloon flight testing in April 2000. The detector test several key techniques needed for the construction of large-area CZT arrays, as required for proposed hard x-ray astronomy missions. Two 10 mm X 10 mm X 5 mm CZT detectors, each with a 4 X 4 array of 1.9 mm pixels on a 2.5 mm pitch, will be mounted in a 'flip chip' fashion on a printed circuit board carrier card; the detectors will be placed 0.3 mm apart in a tiled configuration such that the pixel pitch is preserved across both crystals. One detector is eV Products high-pressure Bridgman CZT, and the other is IMARAD horizontal Bridgman material. A passive shield/collimator surrounded by plastic scintillator surrounds the detectors on five sides and provides an approximately 45 degree field of view. The background spectrum recorded by this instrument will be compared to that measured by a single-element CZT detector fitted with the same passive/plastic collimator but including an active BGO shield to the rear. This detector has been previously flown by us completely shielded by a passive cover. We describe preliminary laboratory result for the various systems, discuss initial background simulations, and describe our plans for balloon flight tests.

Cadmium Zinc Telluride (CZT) is a room temperature semiconductor detector well suited for high energy x-ray astronomy. We have developed a CZT detector with 500 micron crossed strip readout and an advanced electrode design that greatly improves energy resolution. We conducted two balloon flights from Fort Sumner, NM, to study the cross strip detector and a standard planar detector both sensitive in the energy range of 20-350 keV. The flights utilized a total of seven shielding schemes: 3 passive, 2 active and 2 hybrid passive-active. In the active shielding modes, the anti- coincidence shield pulse heights were telemetered for each CZT event, allowing us to study the effect of the shield's energy threshold on the spectral shape and magnitude of the background. We are also developing an energy-dependent background rejection technique based on the charge collection properties of the CZT detector. This technique employs the depth of interaction, as inferred by the ratio of cathode to anode pulse height, to reject events inconsistent with incident source x-rays. The long duration of the May flight enabled us to study activation effects. We present result of the effectiveness of each of the shielding schemes on both detectors, the rejection power of depth of interaction technique on the crossed strip detector, inferred aperture background flux and the level of activation after 22 hours as float.

This paper describes the design and performance of the detectors and electronics developed for the Global UV Imager (GUVI) aboard the NASA TIMED spacecraft, to be launched in May 2000. GUVI employs two alternate design detectors that are compact sealed units with MgF windows, CsI photocathodes, and wedge-and-strip anodes. The focal plane is 15.6 mm X 16.5 mm with images quantized to 176 spectral by 14 spatial pixels, although access to image data over the entire 25-mm dia active area is provided. Moderate detector resolution is achieved at a relatively low gain. Science emphasis is on high throughput, good image stability, and high radiometric accuracy. Significant detector aging is anticipated over an extended mission with sustained high counting rates. Custom hybrid front-end electronics were developed to enable direct coupling to the wedge-and-strip anodes. This eliminates inter-electrode potentials and the associated image distortion and shift with counting rate. A parallel fast channel provides pulse pile-up rejection. XY position, binning, and compression algorithms are performed in software by a fast, radiation- hardened RISC processor. A full-custom ASIC counts input and output rates for each detector.

A study of the effects of secondary electron emission on charge pulses from a microchannel plate (MCPs) photon counting detector with crossed delay line (CDL) anode readout is presented. The detector is a 2D photon counting detector with fast count rate and good spatial resolution being developed at Los Alamos National Laboratory. The CDL anode is constructed of two orthogonal planar pairs of helically wound wires on inner and outer ceramic sides attached to a copper ground plane. The electron cloud event from the MCPs interacts with the wires generating a signal pulse. The electronics that strike the wire with sufficient energy generate secondary electrons. A model is presented for the charge pulses from the CDL anode incorporating the effects of secondary electron emission. An empirical test of the model is conducted with two different wire materials using a demountable MCP/CDL detector. Charge pulses are measured and the results are compared to the model. The result show that the charge pulses from the CDL anode are material dependent and exhibit the general behavior predicted by the model. Secondary electron emission is an integral part of the CDL anode charge pulses and must be considered in further developments of the CDL anode readout.

The GALEX instrument consists of a 50cm normal incidence mirror telescope in combination with a grism, and a dichroic beamsplitter system projecting images onto two detectors simultaneously. The objective of this instrument is to provide sensitive high resolution imaging of galaxies in two bandpasses, with the option of the modest resolution spectroscopy. We are currently developing the microchannel plate, delay line, sealed tube detectors for the Galaxy Evolution Explorer mission to be launched in 2001.

We studied variation efficiencies of CsI, KBr and KI- evaporated reflective planar phototcathodes with the angle of radiation incidence in the spectral range of 25-115 nm. The photocurrent increases with the photon incidence angle for short wavelengths, while it changes only approximately 5 percent at wavelengths approximately 90-115 nm. The theoretical calculations of the photocathode angular response based on the absorption length of the photons and the escape length of the photoelectronics are in a relatively good agreement with the measured data. A detailed study of the detection efficiency angular variation for the microchannel plates with CsI, KI and KBr photocathodes in the spectral range of 25-191 nm is also presented. Heat annealing of the planar photocathodes did not result in any significant variation in their angular response.

The FUSE is an astrophysics satellite designed to make observations at high spectral resolving power in the 90.5- 118.7 nm bandpass. This NASA Origins mission will address many important astrophysical problems, including the variations in the deuterium/hydrogen ratio in the Milky Way and in extragalactic clouds, the kinematics and distribution of O⁵⁺ and other hot gas species in the Galactic disk and halo, the properties of molecular hydrogen in interstellar clouds having a wide variety of temperatures and densities, and the properties of stellar and planetary atmospheres. Between August 1997 and January 1999 an extensive series of vacuum optical test was conducted, first with the spectrograph alone and then with the full satellite in flight-like conditions. Numerous UV spectra were obtained and found to be consistent with performance requirements. We also obtained visible light images with the fine error sensor camera, whose performance will be critical for meeting the demanding pointing requirements of FUSE. In this paper we present estimates of the performance of the instrument, including spectral resolution, line shapes, and effective area. We also present data on the visible light performance of the FES.

The FUSE, successfully launched in June 1999, is an astrophysics satellite designed to provide high spectral resolving power over the interval 90.5-118.7 nm. The FUSE optical path consists of four co-aligned, normal incidence, off-axis parabolic mirrors which illuminate separate Rowland circle spectrograph channels equipped with holographic gratings and delay line microchannel plate detectors. We describe the hardware and methods used for the optical 'end- to-end' test of the FUSE instrument during satellite integration and test. Cost and schedule constraints forced us to devise a simplified version of the planned optical test which occurred in parallel with satellite thermal- vacuum testing. The optical test employed a collimator assembly which consisted of four co-aligned, 381 mm diameter Cassegrain telescopes positioned above the FUSE instrument, providing a collimated beam for each optical channel. A windowed UV light source, remotely adjustable in three axes, was mounted at the focal plane of each collimator. Problems with the UV light sources, including high f-number and window failures, were the only major difficulties encountered during the test. The test succeeded in uncovering a significant problem with the secondary structure used for the instrument cavity and, furthermore, showed that the mechanical solution was successful, the hardware was also used extensively for simulations of science observations, providing both UV light for spectra and visible light for the fine error sensor camera.

The FUSE is an astrophysics satellite designed to provide high resolution spectra with large effective area over the interval 90.5-118.7 nm. The FUSE instrument consists of four co-aligned, normal incidence, off-axis parabolic primary mirrors which illuminate separate Rowland circle spectrograph channels equipped with holographic gratings and delay line microchannel plate detectors.

H₂ and Pt-Ne gal map spectra acquired during the pre- flight optical testing of the FUSE have been studied in order to refine the science data processing procedure. Using automated spectral line identification software and raytrace models of instrument point spread functions, a pre-flight optical performance assessment was completed. The method by which the raw 2D FUSE detector data are converted into calibrated, 1D spectra is described and illustrated using spectrograph integration and test data (I and T). A pre- flight estimate of the resolving power of FUSE is presented along with a thorough description of the associated approximations used to convert measured values of (lambda) /(Delta) (lambda) to resolving power. The PSF of data from spectrograph I and T and optical-end-to-end testing are presented, and the test factors causing their different appearances is discussed.

The FUV Spectrographic Imager for IMAGE is simultaneously imaging auroras at 1218 and 1358 angstrom. It is designed to efficiently reject the Lyman-(alpha) emission line at 1215.7 angstrom. This paper describes the optical calibration. The content is: 1) field of view calibration: detector pixels location with respect to the reference optical cube; distortion matrix used to computer the TDI. b) Radiometric calibration: detector response and linearity; instrument throughput according to its clear aperture and mirror reflection lost; response vs. wavelength and band-rejection certification.

The purpose of the HESSI RAS is to provide information on the roll angle of the rotation spacecraft. Precise knowledge of the roll angle is a necessary ingredient for image reconstruction. The RAS is a continuously operating star scanner that 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 charges one or several pixels above threshold 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. Roll angles at intermediate times are inferred by assuming uniform rotation. With a limiting star magnitude of m_v equals 3 we expect to observe at least 1 star per revolution over 1 year; on the average we will detect about 10 stars/revolution.

The Solar Two Gamma-Ray Observatory is a ground-based instrument designed to detect 20-300 GeV gamma rays by sampling the Cherenkov light generated as gamma rays and cosmic rays interact with the atmosphere. The observatory utilizes the solar two pilot power plant in Barstow, California which has the largest heliostat mirror area in the world. It has over 2,000 heliostats each with about 41 m² mirror are. the total active are is over 75,000 m². Thus, Solar Two Observatory has the potential to be the most sensitive ground-based gamma-ray detector between 20-300 GeV. The secondary mirror system, each capable of viewing 32 heliostats has been designed. The secondary mirror systems also include the photomultiplier tube camera, electronics, and heliostat field. The first secondary camera system is now being manufactured and tested.

We present a novel concept for a MIDEX satellite mission that allows all sky coverage for gamma-ray bursts and hard x-ray transients. The multiscale alternating shadow collimator (MASC) alone allows for arc minute positioning of 1 second bursts 3 times weaker than the BATSE sensitivity. Our scientific objectives include the ability: (a) to detect and monitor thousands of gamma-ray bursts (GRBs) and hard x- ray sources with sensitivity 3-10 times better than BATSE; (b) to solve the gamma-ray burst mystery; (c) to use gamma- ray bursts as probes of cosmological star formation and to measure cosmological parameters; (d) to understand the physics of the high energy radiation from AGNs and BLAZARs; (e) to study the physics of matter in the extreme around black holes and neutron stars; (f) to determine the pulsar birth rate and physical characteristics. The mission concept, MASC concept, and simulations are presented.

MARGIE will be a large-area, wide field-of-view, hard x- ray/gamma-ray imaging telescope capable of providing accurate positions for faint gamma-ray bursts in near-real- time and of performing a sensitive survey of both steady and transient cosmic sources. The instrument is designed to image faint bursts at the low-intensity end of the log N - log S distribution. MARGIE was recently selected by NASA for a mission-concept study for an Ultra Long Duration Balloon flight. We describe a program to develop an instrument based on the new detector technology of either cadmium zinc telluride room-temperature semiconductors or pixelated cesium iodide scintillators viewed by fast timing charge- coupled devices.

IBIS is a space-telescope designed to produce sky images in the 15 keV to 10 MeV energy range with an angular resolution of several arcminutes over a wide field of view. This is obtained by deconvolving the shadow gram projected by a coded mask onto two pixelated detector layers sensitive to the incident radiation interaction position. The upper layer, ISGRI, consists of 16384 CdTe elements operating in the low energy range, while the underlying layer, PICsIT, is made up of 8 identical modules housing altogether 4096 CsI(TI) scintillating crystals coupled to PIN photodiodes operating in the 0.15 to 10 MeV energy range. The expected performances of IBIS were described in a dedicated session of the SPIE Symposium in August 1996, while performances of the PICsIT single detection units have been presented at SPIE in July 1998.

The IBIS instrument is a telescope designed to produce imags of the high-energy sky with an angular resolution of several arcminutes over a wide field of view. This is obtained by use of a coded aperture in conjunction with two separate position sensitive detection planes. The upper layer, ISGRI consists of 16384 CdTe elements and operates between 15 and 600 keV, while the underlying layer PICsIT comprises 8 identical modules housing altogether 4096 CsI(TI) scintillating crystals coupled to PIN photodiodes and functions between 0.15 an 10 MeV. The PICsIT Science Test Equipment has been designed in order to support the functional, environmental and calibration tests of the PICsIT detector at all test levels, including when the PICsIT module is integrate din the IBIS instrument and, afterwards, when IBIS itself is integrated in the spacecraft. To this end, the system has been distributed over two workstations: the On-line Science Console and the Off-line Science Console. The On-line Science Console manages the interfacing with the equipment which commands and acquires the data from the instrument, the near-real time acquisition unpacking and storage of the instrument data, and also allows the operator to continuously monitor the calibration procedure from a scientific point of view. The Off-line Science Console allows the operator to perform more detailed investigations of the instrument performances. The system as implemented for the Engineering Model test and calibration and the current status of the project are described.

Two design concepts for imaging spectrometers are presented. These designs employ first generation, type II holographic gratings to control aberrations and provide excellent spatial resolution with sufficient spectral resolution to isolate individual emission lines over a finite field of view. This effectively creates a narrow band imaging capability. The first designs utilizes a planar substrate with aberration corrected, holographic rulings that is placed in the converging beam of an imaging system. This work demonstrates how the system performance can be substantially increased beyond the performance of an analytic solution using raytrace based computer optimization, which treats all the aberrations simultaneously. The final recording solution and system performance are strongly influenced by the choice of merit functions used in the optimization. The second class of design solutions is based on the classical cassegrain telescope. In these designs aberration corrected, holographic rulings are applied to the parabolic primary or the hyperbolic secondary of the cassegrain telescope. The holographic recording solution for either optic is designed to minimize the aberrations at a specific wavelength. The goal of this work is to explore how the off-axis aberrations of the telescope can be controlled by the holographic rulings at a single wavelength, thus creating an instrument with the high spatial resolution of a cassegrain telescope and the wavelength specific response imposed by the holographic grating.