This paper, “PIMACS (Polarimeter and improved modular anti-coincidence system): an effective instrument concept for x-, gamma-ray monitoring, and polarimetry measurements on the International Space Station," was presented as part of International Conference on Space Optics—ICSO 1997, held in Toulouse, France.
This paper, “Optimized technical and scientific design approach for high performance anticoincidence shields," was presented as part of International Conference on Space Optics—ICSO 1997, held in Toulouse, France.
The X-ray telescope concept for XEUS is based on an innovative high performance and light weight Silicon Pore Optics technology. The XEUS telescope is segmented into 16 radial, thermostable petals providing the rigid optical bench structure of the stand alone XRay High Precision Tandem Optics. A fully representative Form Fit Function (FFF) Model of one petal is currently under development to demonstrate the outstanding lightweight telescope capabilities with high optically effective area. Starting from the envisaged system performance the related tolerance budgets were derived. These petals are made from ceramics, i.e. CeSiC. The structural and thermal performance of the petal shall be reported. The stepwise alignment and integration procedure on petal level shall be described. The functional performance and environmental test verification plan of the Form Fit Function Model and the test set ups are described in this paper. In parallel to the running development activities the programmatic and technical issues wrt. the FM telescope MAIT with currently 1488 Tandem Optics are under investigation. Remote controlled robot supported assembly, simultaneous active alignment and verification testing and decentralised time effective integration procedures shall be illustrated.
In support of future x-ray telescopes ESA is developing new optics for the x-ray regime. To date, mass and volume have made x-ray imaging technology prohibitive to planetary remote sensing imaging missions. And although highly successful, the mirror technology used on ESA’s XMM-Newton is not sufficient for future, large, x-ray observatories, since physical limits on the mirror packing density mean that aperture size becomes prohibitive. To reduce telescope mass and volume the packing density of mirror shells must be reduced, whilst maintaining alignment and rigidity. Structures can also benefit from a modular optic arrangement. Pore optics are shown to meet these requirements. This paper will discuss two pore optic technologies under development, with examples of results from measurement campaigns on samples.
One activity has centred on the use of coated, silicon wafers, patterned with ribs, that are integrated onto a mandrel whose form has been polished to the required shape. The wafers follow the shape precisely, forming pore sizes in the sub-mm region. Individual stacks of mirrors can be manufactured without risk to, or dependency on, each other and aligned in a structure from which they can also be removed without hazard. A breadboard is currently being built to demonstrate this technology.
A second activity centres on glass pore optics. However an adaptation of micro channel plate technology to form square pores has resulted in a monolithic material that can be slumped into an optic form. Alignment and coating of two such plates produces an x-ray focusing optic. A breadboard 20cm aperture optic is currently being built.
Future novel optical systems, for example for EUV lithography and spectroscopy or X-ray applications, must achieve
high optical performance, resulting in stringent requirements on stiffness and stability of the mounted optics.
On the example of silicon pore optics the combination of an isotropic composite ceramic material and silicon could meet
these requirements. In this paper it will be shown that especially for space applications the combination of Cesic(R) and
silicon is advantageous, due to the excellent mechanical properties of Cesic(R) being used for the structural elements. This
combination is especially suitable due to the match of the low coefficient of thermal expansion (CTE) between both
materials. In such a way it is possible to develop, even with two different materials, a thermally stable system that can
function as an optic even at cryogenic temperatures and does not require any adjustment mechanisms.
This paper will discuss the material properties, present results on concrete applications for potential astrophysical science
missions and show some conceptual designs and applications of this material combination for future space missions.
XEUS, the 'X-ray Early Universe Spectroscopy Mission', is a potential candidate for inclusion into the Cosmic Visions 1525 Science Programme of the European Space Agency ESA [1,2]. It is being studied jointly with the Japanese Aerospace Exploration Agency JAXA.
The newly developed Silicon-based High resolution Pore Optics (HPO) combines low mass density with good angular resolution, and enables the development of novel mission design concepts for the implementation of a new generation of space based X-ray telescope [3, 4, 5]. This optics technology allows also for the application of complex reflective coatings [6], improving the effective area of the telescope and permitting an enhancement in the engineering of the desired response function.
This paper gives an overview of the telescope optical design and optical bench architecture, including the deployment scheme. Further, the performance predictions based on ray tracing are discussed and the overall telescope design of XEUS is presented.
N. Kappelmann, J. Barnstedt, W. Gringel, K. Werner, H. Becker-Roβ, S. Florek, R. Graue, D. Kampf, A. Reutlinger, C. Neumann, B. Shustov, M. Sachkov, V. Panchuk, M. Yushkin, A. Moisheev, E. Skripunov
The World Space Observatory Ultraviolet (WSO/UV) is a multi-national project grown out of the needs of the astronomical community to have future access to the ultraviolet range of the spectrum. The development of the WSO/UV S/C and the telescope is headed by the Russian Federal Space Agency (Roscosmos). The mission is scheduled to be launched in 2010 into the L2 orbit. The WSO/UV consists of a single Ultraviolet Telescope, incorporating a primary mirror of 1.7 m diameter feeding UV spectrometer and UV imagers. The UV spectrometer comprises three different single spectrographs, two high resolution echelle spectrographs - the High Resolution Double Echelle Spectrograph (HIRDES) - and a low dispersion long slit instrument. Within the HIRDES the spectral band (102 - 310 nm) is separated into two echelle spectrographs covering the UV range between 174- and 310 nm (UVES) and VacuumUV range between 102 and 176 nm (VUVES) with a very high spectral resolution of > 50000. Each spectrograph encompass a stand alone optical bench structure with a fully redundant high speed MCP detector system, the optomechanics and a network of mechanisms with different functionalities. The fundamental technical concept is based on the heritage of the two previous ORFEUS SPAS missions. The phase B1 development activities are described in this paper under consideration of performance aspects, design drivers, the related trade offs (e.g. mechanical concepts, material selection etc.) and the critical functional and environmental test verification approach. Furthermore the actual state of the other scientific instruments of the WSO/UV (e.g. UV imagers) project is described.
The XEUS petals encompass the optical bench structure of the stand alone X-Ray Optical Units (XOU) based on the
high performance and light weight Silicon Pore Optics technology. The performance aspects under consideration of the
design drivers, the related trade offs (e.g. mechanical concepts, material selection, XOU butting efficiency etc.) and the
current development activities wrt. the design, manufacturing, assembly and the functional and environmental test
verification approach of the Form Fit Function Model are described in this paper. Special emphasis is given to the critical
external optical and mechanical interfaces coherent to the mission design, e.g. the Mirror S/C frame work structure and
the Detector S/C. The technology program is based on the heritage achieved within the context of the XMM/Newton
telescope development. The investigations of the correlated programmatic aspects towards the FM production by
application of effective robot system supported assembly procedures shall be illustrated.
The Photoconductor Array Camera and Spectrometer (PACS) is developed by an European consortium led by MPE, Germany. It is one of 3 cryogenic focal plane instruments of the Herschel Space Observatory, 1 of the 4 cornerstone missions within the ESA Horizon 2000 programme. The instrument will cover the wavelength regime from 60-210μm to explore the cold universe.
The input beam is distributed to 4 advanced IR-detectors - 2 Ge:Ga photoconductor arrays for spectroscopy and 2 bolometer detector arrays for photometry - via a complex and very compact optomechanical layout with approx. 50 passive and active optical mirrors and 4 precision mechanisms.
The paper will give an overview about the final optomechanical and thermal design of the thermal mass dummy and the cryo qualification model of the PACS Focal Plane Unit (FPU).
The manufacturing and coating techniques of the lightweight aluminum mirrors applied to fulfill the infrared performance requirements even under cryogenic conditions and the alignment plan and optical verification concept in the visible range is outlined.
The advanced manufacturing and thermal treatment procedures for the all aluminum optical bench are described in detail. Special emphasis is given to the dedicated development and verification efforts of a sophisticated IR Black Paint with extremely high IR-absorption used for effective straylight suppression.
The conceptual architecture of the 2 very temperature stable and homogenous calibration sources is reported.
The German Instrument for Multi-channel Photometry and Astrometry (DIVA), dedicated to the German (DLR) small extraterrestrial satellite program, is intended as a kind of technology precursor mission to GAIA. DIVA is scheduled for launch in 2004 and shall perform a sky survey to measure within 2 years life time the positions, parallaxes, magnitudes, etc. of about 35 million stars.
The main instrument, covering the spectral range of 400-1000nm, observes 2 fields of view (0.6° x 0.77°) by a single Focal Plane Assembly (FPA). The focal length is 11200mm. The DIVA Optomechanics is based on a high precision Three Mirror Anastigmat (TMA) concept with 8 mirrors, 5 of them flat. An extremely high short term stability (torsion tolerance) of 0.3 mas over 10h only has to be realized only by passive means to achieve the astrometrical performance requirements. The paper describes the phase B2 design activities wrt. the optomechanical and thermal design of the main instrument. Special emphasis is given to an exhausting, but very pragmatic thermomechanical and optical performance trade off between a cost effective athermal design concept, applying mirrors and an optical bench made from a specially treated isotropic aluminum alloy, and a thermally stable hybrid material concept based on a Carbon Fiber Reinforced Plastics (CFRP) sandwich structure and Zerodur mirrors. The selection of the final baseline design solution shall be reported. According to the very high long and short scale surface properties of the candidate aluminum mirrors a sophisticated manufacturing procedure was established based on conventional and ion beam polishing techniques. The representative breadboard mirror test results will be given.
The Photoconductor Array Camera and Spectrometer (PACS) is one of the scientific core instruments on board of the ESA Horizon 2000 Cornerstone Mission FIRST: The PACS instrument can operate as a dual-band imaging photometer or as an integral-field spectrometer. The scientific instrument, designed for remote measurements of astronomical far- infrared emissions, incorporates several temperature levels between 1.7 and 15 K in order to keep the self-emission of the instrument at a low level.
Closed meshed instrumentation or sensor networks with conventional sensors for temperature and strain measurements may result in excessive penalties in terms of weight constraints, sensitivity to environmental conditions and complex interfaces. The FOS is a multiplexed sensor system for up to 50 single strain and temperature measurement points comprising of a fiber network and an optoelectronic unit. The FOS sensor was designed and developed by Kayser-Threde, Munich, for demanding space environment, but can also be emphasized as a promising sensor technology with high potential for non-space applications. A Fiber Optic Sensor (FOS) measures strain and temperature by means of wavelength shifts due to tensile stress on a Bragg grating. Slightly shifts in the reflected wavelength are proportional to temperature or strain acting on the fiber at the corresponding grating location. Dependent on the fixation of the fiber to the structure, either floating or attached to the surface, local thermal or mechanical loads can be determined. The fibers can be mounted at the monitored structure or embedded (e.g. into composite materials). The FOS sensor is very suitable for structural health monitoring of large structures, i.e. to determine thermal and mechanical load profiles during operation, assessment of residual strength of structural elements or to detect irregular conditions. In comparison to conventional sensors like thermocouples and strain gauges, a FOS network significantly reduces the amount of required Front End Electronics (FEE) and harness.
Health monitoring passenger experiments will be flown on board of X-38 re-entry demonstrator as precursor to reusable launch vehicles such as the Crew Rescue Vehicle. Environmental load impacts and load critical conditions of the Thermal Protection System will be monitored with advanced in-flight and on-ground sensor instrumentation, the structural and functional integrity assessed, and potential consequences regarding the probability of hazardous failure or reduced life time evaluated. Intelligent health monitoring systems can streamline operational and maintenance costs while at the same time satisfying the high safety and reliability requirements. This imposes more stringent requirements on a network of sensors based on innovative technologies such as fiber optics, acoustic emissions, etc. The current development activities within the frame of the national technology program X-38/TETRA, the specific sensor features and the diagnostic expert system for data analyses will be highlighted and discussed in this paper.
The high precision mirror replication technology with electro-formed Nickel was substantially optimized within projects such as JET-X and XMM. Based on this experience demonstrated on several hundred mirror shells with optical surface areas up to 1.3 m2 a new ultra lightweight mirror technology has been developed, enabling the production of low cost, isotropic, precision meniscus like reflectors highlighting excellent optical performance. In principle, any reflector thickness (typically 200 mm) can be electro-formed with the desired curvature and surface characteristics which is close to the optical quality of the mandrel (master). Any spherical or flat shape, including even offset elliptical reflectors, can be produced. No honeycomb or alternative stiffening structure is envisaged since the objective is to achieve a lightweight, perfectly isotropic reflector. A specific bonding between reflector meniscus and supporting structure made from Nickel is provided which avoids the introduction of local internal stress concentrations due to the final quasi-monolithic configuration. This technology can cover mirror dimensions up to several meters for astronomical, spaceborne and ground based telescopes (e.g. FIRST primary mirror) and radio antennas in the (sub)millimeter wave length range.
For the measurement of astronomical gamma ray radiation in the energy range 50 keV to several MeV usually photomultiplier tubes (PMT) with scintillation crystals are used. However, due to the internal detection mechanism high voltage and single photon counting are required leading to heavy and structurally unpractical systems. Even APD's (avalanche photodiodes) do not circumvent the problem of the high voltage. Recent improvements in the performance of semiconductor detectors allow the use of large area and low noise pin photodiodes as innovative scintillation detectors with 40 - 100 V operating voltage only. Tl-doped CsI as scintillation crystal with a superior light yield has not only a much higher photon output compared to the light yield of pure CsI and BGO crystals which are used for the gamma ray detection with PMTs, but has also a perfect matching of spectral properties of the photodiode. This paper presents a comprehensive comparison with conventional PMT scintillation detector systems and the development activities of full size breadboards with such a photodiode/CsI(Tl) detector set-up. The relevant functional performance test results have shown the high technical maturity of this detector system and the principal feasibility for the application either in the INTEGRAL spectrometer and imager anticoincidence shield (ACS) or in image central detector system. The dedicated ACS configuration design featuring optimized mass budget combined with high gamma ray stopping efficiency is figured.
The 1-m STARS telescope was one of the five candidates for the coming ESA medium size (M3) mission. Based on the very compact Triply Reflecting Telescope concept, the STARS telescope provides diffraction limited image performance over a large field of view (+/- 0.75 degree(s)). Two different focal plane instruments, the Astero Seismology Detector and the Activity Line Monitor observe simultaneously in different wavelength bands in the range from 110 to 750 nm. Within the frame of an ESTEC conducted phase A study, the optical, mechanical, and thermal design of the complete telescope assembly including the accommodation on the service module has been investigated. A stiff and lightweight hexapod trusswork structure with struts from carbon fiber reinforced composites has been worked out as the most advantageous concept with respect to mass, opto- mechanical, and thermal properties. The major issues were the maintenance of an axial distance stability of +/- 10 micrometers between primary and secondary mirror as well as the fulfillment of certain thermal requirements for the two scientific instruments (Activity Line Monitor and Asteroseismology Detector). The finally chosen concept has a fully reflective optical design with higher order aspheric optical surfaces, a passive thermal design, is extremely lightweight (< 190 kg), and has a high stiffness (all eigenfrequencies are above 60 Hz). For the optics, a simpler approach with only conical reflective surfaces and an additional refractive correction element has been investigated.
High performance x-ray Wolter I telescopes require especially at high energies excellent specular mirror shell reflectivity features to collect grazing incidence radiation. Applying galvanoplastic techniques the surface quality of complementary mandrels can be replicated on the mirror shells with negligible degradation only. Therefore, adequate surface finish by advanced superpolishing of the mandrels is a strong prerequisite in order to improve the specularly reflected portion of the incoming x-ray light. For that reason, a new surface technology was developed within the frame of the JET-X mirror assembly project providing reduced high frequency components of the surface roughness correlated with the reduction of mandrel surface scattering (diffuse reflection). At high x-ray energies (8.1 keV) the measured encircled energy image of mirror shells replicated from these mandrels was up to 3 times better than from untreated mandrels.
The Rear Slit Camera (RSC) will be used in the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) instrument on SOHO to investigate the exact position and quality of the solar limb imaged on the entrance slit of the SUMER spectrometer. The diffracted visible sun light will be focused on an image sensor array. The analogous signals are transferred to the internal RSC electronics and transferred to the SUMER Data Processor Unit (DPU). According to the major design constraints redundancy of the optomechanics and electronics of the RSC was not required, because the reliability of the camera was not estimated to be system critical. The scientific objects, the technical development and verification of this camera shall be detailed. The achievements of the tight cooperation between Kayer-Threde and the Max Planck Institute for Aeronomy, in terms of technical performance and costs shall specially be emphasized.
An imaging spectrograph with high spectral resolution (< 0.55 nm) operating in the UV region between 300 - 320 nm is presented. The instrument uses Differential Optical Absorption Spectroscopy (DOAS) to monitor the SO2 total content in the earth's atmosphere from a sun synchronous orbit. The design of the entire instrument including wide-angle optics (+/- 57.5 degree(s)), opto- mechanics and sensor electronics (low light CCD application) and the in-flight calibration unit are described. The requirements on stability and calibration accuracy of the instrument caused by the DOAS method are outlined.
The alignment concept of ORFEUS, a short-term scientific space payload scheduled for launching by the STS in January 1993, is discussed. ORFEUS comprises two alternatively operating spectrometers (Echelle and Rowland) implemented in a CFC telescope with a 4-m tube length and an aperture of 1000 mm. The lightweight primary mirror has a focal length of 2426 mm. In order to achieve the required spectrometric high telescope resolution in the UV range (40-125 nm), a sophisticated alignment concept was developed. The centering of the alignment diaphragm (diameter: 15 microns) in the focus of the primary mirror has to be provided in the vertical tube position by means of an autocollimation telescope. The spectrometers have to be integrated into the horizontal telescope aligned within a special antigravity device to reduce optical surface deformations and to ensure the optical performance of the primary. The alignment of all optical components is to be performed in the visible spectral range.
The ORFEUS instrument is the first of a few missions which have to be flown
with the ASTRO-SPAS satellite. The instrument consists of an on-axis telescope
with 1 m primary mirror together with two focal plane spectrometers.
The main scientific objectives are spectroscopic easureents of cosmic radiation
sources in the temperature region between 10 to 10 K.
The Rowland spectrometer which operates in the spectral region between 40 nm to
120 rim is supplied by the Space Astronomy Group (SAC) of the University of
Berkeley, the Echelle spectrometer was designed by the Landessternwarte Heidelberg
(LSW, FRG) and covers the spectral region between 90 nm to 125 nm.
The overall scientific responsibility is at the Astronomisches Institut TUbingen
(AlT, FRG).
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