Cryogenic optical performance of the ASTRO-F SiC telescope

The lightweight cryogenic telescope on board the Japanese infrared astronomical satellite, ASTRO-F, which is scheduled to be launched early in 2006, forms an F/6 Ritchey-Chretien system with a primary mirror of 710 mm in diameter. The mirrors of the ASTRO-F telescope are made of sandwich-type silicon carbide (SiC) material, comprising a porous core and a chemical-vapor-deposited coat of SiC on the surface. To estimate the optical performance of the flight model telescope, the telescope assembly was tested at cryogenic temperatures, the total wavefront errors of which were measured by an interferometer from outside a liquid-helium chamber. As a result, the wavefront error obtained at 9 K shows that the imaging performance of the ASTRO-F telescope is diffraction limited at a wavelength of 6.2 microm, which is a little worse than our original goal of diffraction-limited performance at 5.0 microm.     

Imaging performance of telescope mirrors for far-ultraviolet astronomy

We describe image testing, surface metrology, and modeling of telescope mirrors (0.5 m in diameter, f/4.3) for the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite. Laboratory image testing of wavelengths in the visible, vacuum, and midultraviolet validated a theoretical analysis by use of the Optical Surface Analysis Code (OSAC). Our modeling is based on surface metrology, including measurements of figure, midfrequency error, and microroughness. This combination of metrology, out-of-band performance testing, and modeling verified that the mirrors would meet mission requirements. We use OSAC to predict the FUSE telescope's far-ultraviolet (90-120-nm) point-spread function and assess its effect on instrument efficiency. The mirrors have a 90% encircled energy diameter of 1.5 arc sec at lambda = 100 nm. Including the effects of spacecraft pointing error, the mirrors have a predicted average slit transmission at lambda = 100 nm of approximately 87% and 96% for the 1.25- and 4-arc sec-wide spectrograph slits, respectively, where the required transmissions are 50% and 95%.     

Optical performance of the 6.5-m off-axis new planetary telescope

We describe an off-axis design for a 6.5-m astronomical telescope optimized for low scattered light and low emissivity. This is part of a new concept for an instrument that we call the New Planetary Telescope. We show how the geometric optical performance can equal that of an on-axis conventional telescope while the diffractive performance fundamentally surpasses conventional telescopes because of the absence of pupil obstruction. The decentered concept also allows wide-field and versatile instrumentation configurations that are not possible with more-conventional designs.     

Fine-error-sensor camera designs and performance for the Lyman Far Ultraviolet Spectrographic Explorer telescope

The Lyman Far Ultraviolet Spectrographic Explorer telescope is a glancing-incidence type with a highly curved focal surface. Because the instrument is required to guide on stars in the visible range fainter than m(v) = 16 over at least a 10-arcmin field, it is necessary to reimage the field to one, which is sufficiently flat and of appropriate scale for registration by a CCD. We present two camera designs that satisfy this requirement and discuss their overall performance.     

Patterned armor performance evaluation

Patterned armor is characterized by an array of repeating cells, such as tiled ceramic armor or reactive armor boxes. Performance characteristics of an ideal patterned armor with respect to multiple hits are discussed, and the types of single-shot ballistic data needed to quantify that performance are presented. An approach to use these data is developed to provide a quantitative measure (probability of nonperforation after a given number of impacts) of the patterned armor performance against multiple impacts. This performance measure can then be compared to a well-posed multiple-hit criterion to assess whether the patterned armor meets the criterion.     

Supermirror hard-x-ray telescope

The practical use of a grazing x-ray telescope is demonstrated for hard-x-ray imaging as hard as 40 keV by means of a depth-graded d-spacing multilayer, a so-called supermirror. Platinum-carbon multilayers of 26 layer pairs in three blocks with a different periodic length d of 3-5 nm were designed to enhance the reflectivity in the energy range from 24 to 36 keV at a grazing angle of 0.3 deg. The multilayers were deposited on thin-replica-foil mirrors by a magnetron dc sputtering system. The reflectivity was measured to be 25%-30% in this energy range; 20 mirror shells thus deposited were assembled into the tightly nested grazing-incidence telescope. The focused hard-x-ray image was observed with a newly developed position-sensitive CdZnTe solid-state detector. The angular resolution of this telescope was found to be 2.4 arc min in the half-power diameter.     

Step-zoom dual-field-of-view infrared telescope

The design of a dual-field-of-view telescope for an 8-12-microm imaging waveband is described. Preliminary calculations are made to determine the first-order parameters of the narrow- and the wide-field modes. To achieve a switchable dual-field-of-view system, one use an optical configuration based on the axial motion of a single lens group along the optical axis. The same lens is also used for focusing at near objects and for athermalization by small axial movement. A total of six lenses with one conic surface are used in the design, making the telescope cost effective and lightweight. The final optical design is presented, along with the aberrations curves and modulation transfer function plots, showing excellent performance in both fields of view.     

Broadband antihole photon sieve telescope

A broadband-corrected optical telescope has been constructed from a photon sieve with five million holes. Through careful optimization of hole size, this "antihole" sieve has holes centered on the dark underlying Fresnel zones. The diffraction-limited performance of a 1 m focal-length, f/10 element is demonstrated with a view toward constructing large lightweight telescopes for space applications.     

X-ray telescope onboard Astro-E. III. Guidelines to performance improvements and optimization of the ray-tracing simulator

We present a detailed study of the performance of the Astro-E x-ray telescope (XRT) onboard the Astro-E satellite. As described in preceding papers the ground-based calibrations of the Astro-E XRT revealed that its image quality and effective area are somewhat worse than that expected from the original design. Conceivable causes for such performance degradation are examined by x-ray and optical microscopic measurements at various levels, such as individual reflectors, sectors, and quadrants of the XRT and their alignments. We can attribute, based on detailed measurements, the degradation of the image quality to a slope error in the individual reflectors and the positioning error of reflectors. As for the deficit of the effective area, the shadowing of x rays within the XRT body is the dominant factor. Error budgets for the performance degradation of the Astro-E XRT are summarized. The ray-tracing simulator, which is needed to construct the response function for arbitrary off-axis angles and spatial distributions of any celestial x-ray sources, has been developed and tuned based on the results of detailed measurements. The ray-tracing simulation provides results that are consistent within 3% with the real measurement except for large off-axis angles and higher energies. We propose, based on knowledge obtained from all the measurements and simulations, several plans for future developments to improve the performance of the nested thin-foil mirrors.     

Relative performance evaluation and contract externalities

We consider the incentive characteristics of optimal linear contracts based on relative performance evaluation (RPE) for managers under moral hazard in imperfectly competitive product markets. Each contract influences the quantity choices of all competing agents causing contract externalities that affect the principals’ contracting game. We analyze the relations between the optimal extent of RPE and several firm and market characteristics, allowing for heterogeneous firms and idiosyncratic firm risk. In general, we find non-monotonic comparative static results regarding the influence of market and firm-specific risk, the industry’s competitiveness, and the correlation of the firms’ profit.     

Action performance evaluation in video sequences

In this paper, we propose a computer vision scheme for action performance evaluation in video sequences. Different from action recognition algorithms that aim at the classification of an unknown action from a set of predefined reference actions, the action evaluation system scores the action performance of a trainee with respect to professional trainers. It can be applied to sports, exercise fitness and rehabilitation evaluation. The global spatiotemporal representation extended from the Motion History Image is used to describe space–time changes of an action in videos. A self-comparison mechanism that reconstructs the trainee’s action as a linear combination of the trainers’ temporal templates is used to measure the deviation. An exponential utility function converts the reconstruction error into an understandable score between 0% and 100%. Test results on table-tennis scenarios have shown the effectiveness of the proposed method. It is also computationally very fast for on-line, real-time feedback of action performance.     

Fuzzy approach to dependability performance evaluation

This paper presents a model for dependability performance evaluation by fuzzy sets utilization. Basic dependability indicators (reliability, maintainability and maintenance support) are used for the analysis of technical systems' conditions from the aspects of design, construction, maintenance and logistics. These indicators as well as associated dependability expressions itself are described by linguistic variables, which are characterized by a membership function to the defined classes. The proposed model is primarily appropriate for introduction, analysis and synthesis of information related to quality of systems in operation. Such data are often available only as experts' judgment and estimations. A practical engineering example (mechanical system at bucket wheel excavator) has been presented to demonstrate the proposed dependability analysis and synthesis model. Copyright © 2008 John Wiley & Sons, Ltd.     

Multiple-path telescope: third-order design

Exact results for the magnification and effective focal length of a multiple-path telescope are presented. We present analytical results for the third-order design of this system, using the Seidel sums for the five aberration terms. Numerical calculations are used throughout to corroborate these results. Third-order aberrations remain small or at least stable as the number of paths is increased.     

A new measure for supplier performance evaluation

Recently the concept of dimensional analysis was used to propose a supplier performance measure and to obtain an index called the VPI (Vendor Performance Index). Usually the performance criteria used in supplier performance evaluation include quantitative and qualitative criteria. Here a new supplier performance measure is proposed as an alternative to the VPI. For qualitative criteria, a two-directional consideration is used instead of a one-directional approach, which results in only a single score. The fuzzy bag method is used to compensate for blindness in human judgement. Then all scores for quantitative and qualitative criteria are combined in an intuitive sum of weighted averages called the SUR. The SUR is illustrated and compared with the VPI by means of two examples.     

光学太阳反射器的性能评价试验规范

航天器在地面待发射期间加空间实际飞行过程中，热控元件ＯＳＲ要遇到各种地面和空间环境。为了航天器的可靠和长寿命，必须对所制备的ＯＳＲ涂层进行各种地面和空间环境试验并对其各项性能检验与考核，就这一系列试验的目的和规范进行了讨论。