Scott M. Owens

Characterization of the supermirror hard-x-ray telescope for the InFOCμS balloon experiment

A hard-x-ray telescope is successfully produced for balloon observations by making use of depth-graded multilayers, or so-called supermirrors, with platinum-carbon (Pt/C) layer pairs. It consists of four quadrant units assembled in an optical configuration with a diameter of 40 cm and a focal length of 8 m. Each quadrant is made of 510 pieces of coaxially and confocally aligned supermirrors that significantly enhance the sensitivity in an energy range of 20-40 keV. The configuration of the telescope is similar to the x-ray telescope onboard Astro-E, but with a longer focal length. The reflectivity of supermirrors is of the order of 40% in the energy range concerned at a grazing angle of 0.2 deg. The effective area of a fully assembled telescope is 50 cm2 at 30 keV. The angular resolution is 2.37 arc min at half-power diameter 8.0 keV. The field of view is 12.6 arc min in the hard-x-ray region, depending somewhat on x-ray energies. We discuss these characteristics, taking into account the figure errors of reflectors and their optical alignment in the telescope assembly. This hard-x-ray telescope is unanimously afforded in the International Focusing Optics Collaboration for muCrab Sensitivity balloon experiment.

Constellation-X spectroscopy x-ray telescope optical assembly pathfinder image error budget and performance prediction

The Constellation-X mission is a follow-on to the current Chandra and XMM missions. It will place in orbit an array of four X-ray telescopes that will work in unison, having a substantial increase in effective area, energy resolution, and energy bandpass over current missions. To accomplish these ambitious increases new optics technologies must be exploited. The primary instrument for the mission is the Spectroscopy X-Ray Telescope (SXT), which covers the 0.21 to 10 keV band with a combination of two x-ray detectors: a reflection grating spectrometer with CCD readout and a micro-calorimeter. Mission requirements are an effective area of 15,000 cm2 near 1 keV and a 15 arc-sec (HPD) image resolution with a goal of 5 arc-sec. The Constellation-X SXT uses a segmented design with lightweight replicated optics. A technology development program is being pursued with the intent of demonstrating technical readiness prior to the program new start. Key elements of the program include the replication of the optical elements, assembly and alignment of the optics into a complete mirror assembly and demonstration of production techniques needed for fabrication of multiple units. These elements will be demonstrated in a series of engineering development and prototype optical assemblies which are increasingly flight-like. In this paper we present an image angular resolution error budgets for the SXT and for the Optical Assembly Pathfinder #2 (OAP2), the first of engineering development units intended to be tested in x-rays. We describe OAP2 image error sources and performance analyses made to assess error sensitivities. Finally we present an overall prediction of as-tested imaging performance in the x-ray test facility.

First light of a hard-x-ray imaging experiment: the InFOCuS balloon flight

As technological and scientific path-finder towards future observatory missions, a balloon-born hard X-ray imaging observation experiment InFOCμS has been developed. The payload has flown four times since 2000. In its 2004 Fall flight campaign InFOCμS successfully achieved first scientific observations of multiple astronomical objects from galactic compacts to cluster of galaxies. Significant signal has been detected from bright galactic objects while analysis of extragalactic objects is underway. InFOCμS plans additional and upgraded telescope-detector system as early as 2006. High energy telescope for nuclear gamma-ray line observations is under planning.

Development of supermirror hard x-ray telescope and the results of first observation flight of InFOCuS flight observation

The development of hard X-ray focusing optics is widely recognized as one of key technologies for future X-ray observatory missions such as NeXT(Japan), Constellation-X(US) and possibly XEUS(Europe). We have developed hard X-ray telescope employing depth-graded multilayers, so-called supermirrors. Its benefit is to reflect hard X-rays by Bragg reflection at incidence angles larger than the critical angle of total external reflection. We are now continuously fabricating platinum-carbon(Pt/C) supermirror reflectors for hard X-ray observations. In this paper we focus on our development of the hard X-ray telescope for the first balloon flight observation (InFOCuS) and its results. InFOCuS is an international balloon-borne hard X-ray observation experiment initiated by NASA/GSFC. InFOCuS hard X-ray telescope have been jointly developed by Nagoya University and GSFC. The telescope is conical approximation of Wolter-I optics with 8m focal length and 40cm diameter. It consists of 255 nested ultra-thin reflector pairs with incidence angles of 0.10 to 0.36deg. Reflectors are coated with Pt/C supermirrors with periodic length of 2.9 to 10nm and bi-layer number of 25 to 60, depending on incidence angles. The effective area and imaging quality are expected as 100 cm2 at 30 keV and 2 arcmin in half power diameter, respectively. The InFOCuS experiment was launched on July 5, 2001, from National Scientific Balloon Facility in Texas, USA. We successfully observed Cyg X-1, chosen for a calibration target, in 20-40keV energy band. We are planning to carry out next flight for scientific observations as soon as additional telescopes, detectors, and upgraded gondola system are implemented.

Constellation-X SXT optical alignment Pathfinder 2: design, implementation, and alignment

The Constellation-X SXT mirrors and housings continue to evolve toward a flight-like design. Our second-generation alignment housing, the Optical Alignment Pathfinder 2 (OAP2), is a monolithic titanium structure that is nested inside the OAP1 alignment jig, described in a previous paper (J. Hair, et. al., SPIE 2002). In order to perform x-ray tests in a configuration where the optical axis is horizontal, and continue to develop more flight-like structures, we needed to design a strong, but lightweight housing that would impart minimal deformations on the thin segmented mirrors when it is rotated from the vertical orientation used for optical alignment to the horizontal orientation that is used for x-ray testing. This paper will focus on the design of the OAP2 housing, and the assembly and alignment of the optics within the OAP1 plus OAP2 combination using the Centroid Detector Assembly (CDA). The CDA is an optical alignment tool that was successfully used for the HRMA alignment on the Chandra X-ray Observatory. In addition, since the glass we are using is so thin and flexible, we will present the response of the optical alignment quality of a Wolter-I segment to known deformations introduced in by the OAP1 alignment housing.

Recent Progress on the Constellation-X Spectroscopy X-Ray Telescope (SXT)

The Constellation X-ray Observatory consists of four identical spacecraft, each carrying a complement of high sensitivity X-ray instrumentation. At the heart of each is the grazing incidence mirror of the Spectroscopy X-ray Telescope (SXT). This mirror has a diameter of 1.6 m, a focal length of 10 m, mass not exceeding ~650 kg. The required angular resolution is 15 arc seconds and the effective area at 1 keV must exceed 7,500 cm2. Achieving these performance requirements in a cost effective way within the allocated mass is accomplished via a modular design, incorporating lightweight, multiply-nested, segmented Wolter Type I X-ray mirrors. The reflecting elements are composed of thin, thermally formed glass sheets, with epoxy-replicated X-ray reflecting surfaces. Co-alignment of groups of reflectors to the required sub-micron accuracy is assisted by precision silicon microstructures. Optical alignment incorporates the Centroid Detector Assembly (CDA) originally developed for aligning the Chandra mirror. In this talk we present an overview of recent progress in the SXT technology development program. Recent efforts have concentrated on producing an engineering unit that demonstrates all the key fabrication and alignment processes, and meets the angular resolution performance goal. Additionally, we describe the initial steps toward flight mirror production, anticipating a Constellation-X launch early in the next decade.

X-ray testing Constellation-X optics at MSFC's 100-m facility

As NASA’s next facility-class x-ray mission, Constellation X will provide high-throughput, high-resolution spectroscopy for addressing fundamental astrophysical and cosmological questions. Key to the Constellation-X mission is the development of lightweight grazing-incidence optics for its Spectroscopy X-ray Telescopes (SXT) and for its Hard X-ray Telescopes (HXT). In preparation for x-ray testing Constellation-X SXT and HXT development and demonstration optics, Marshall Space Flight Center (MSFC) is upgrading its 100-m x-ray test facility, including development of a five degree-of-freedom (5-DoF) mount for translating and tilting test articles within the facility’s large vacuum chamber. To support development of alignment and assembly procedures for lightweight x-ray optics, Goddard Space Flight Center (GSFC) has prepared the Optical Alignment Pathfinder Two (OAP2), which will serve as a surrogate optic for developing and rehearsing x-ray test procedures. In order to minimize thermal distortion of the mirrors during x-ray testing, the Harvard-Smithsonian Center for Astrophysics (CfA) has designed and implemented a thermal control and monitoring system for the OAP2. CfA has also built an aperture wheel for masking and sub-aperture sampling of the OAP2 to aid in characterizing x-ray performance of test optics.

InFOCμS balloon-borne hard x-ray experiment with multilayer supermirror x-ray telescope

We have been developing the high throughput hard X-ray telescope, using reflectors coated with the depth graded multilayer known as supermirror, which is considered to be a key technology for future satellite hard X-ray imaging missions. InFOC(mu)

Characterization and performance of the InFOCμS 20-40 keV x-ray focusing mirror

S, the International Focusing Optics Collaboration for (mu) -Crab Sensitivity is the project of the balloon observation of a cosmic hard X-ray source with this type of hard X-ray telescope and CdZnTe pixel detector as a focal plane imager. For the fist InFOC(mu) S balloon experiment, we developed the hard X-ray telescope with outermost diameter of 40cm, focal length of 8m and energy band pass of 20-40 keV, for which Pt/C multilayer was used. From the pre-flight X-ray calibration, we confirmed its energy band and imaging capability of 2 arcmin HPD and 10 arcmin FOV of FWHM, and a effective area of 50 cm2 for 20-40 keV X-ray. We report the current status of our balloon borne experiment and performance of our hard X-ray telescope.

Toward a complete metrologic solution for the mirrors for the Constellation-X Spectroscopy x-ray telescope

Mass production of replicated thin aluminum x-ray reflecting foils for the InFOC(mu) S (International Focusing Optics Collaboration for Micro-Crab Sensitivity) balloon payload is complete, and the full mirror has been assembled. InFOC(mu) S is an 8-meter focal length hard x-ray telescope scheduled for first launch in July 2001 and will be the first instrument to focus and image x-rays at high energies (20-40 keV) using multilayer-based reflectors. The individual reflecting elements are replicated thin aluminum foils, in a conical approximation Wolter-I system similar to those built for ASCA and ASTRO-E. These previous imaging systems achieved half-power-diameters of 3.5 and 1.7-2.1 arcminutes respectively. The InFOC(mu) S mirror is expected to have angular resolution similar to the ASTRO-E mirror. The reflecting foils for InFOC(mu) S, however, utilize a vertically graded Pt/C multilayer to provide broad-band high-energy focusing. We present the results of our pre-flight characterization of the full mirror, including imaging and sensitivity evaluations. If possible, we will include imaging results from the first flight of a multilayer-based high-energy focusing telescope.