MICADO, the Multi-AO-Imaging-Camera and Spectrometer for Deep Observations, is one of the first light instruments for the future 40 m class Extremely Large Telescope (ELT). MICADO utilizes the advanced laser guide star multiconjugate adaptive optics system MCAO developed by the MAORY consortium and the jointly developed singleconjugate adaptive optics system (SCAO). We present an overview on the conceptual design of the MICADO Cold Optical Instrument (COI) which comprises the infrared focal plane imager with its 3 x 3 4k2 HgCdTe detector array and a compact cross-dispersing slit spectrometer operating in the spectral range of 0.8 to 2.4 μm. High contrast imaging is enabled via a classical configuration of coronagraph and Lyot stops. The paper summarizes the MICADO COI interchangeable optics, its cryogenic implementation together with the modular opto-mechanical configuration of the cryo-mechanisms and the cryo-vacuum cooling system, which consists of a continuous LN2 flow cryostat.
By adding a dedicated coronagraph, ESO in collaboration with the Breakthrough Initiatives, modifies the Very Large Telescope mid-IR imager (VISIR) to further boost the high dynamic range imaging capability this instru- ment has. After the VISIR upgrade in 2012, where coronagraphic masks were first added to VISIR, it became evident that coronagraphy at a ground-based 8m-class telescope critically needs adaptive optics, even at wavelengths as long as 10μm. For VISIR, a work-horse observatory facility instrument in normal operations, this is ”easiest” achieved by bringing VISIR as a visiting instrument to the ESO-VLT-UT4 having an adaptive M2. This “visit” enables a meaningful search for Earth-like planets in the habitable zone around both α-Cen1,2. Meaningful here means, achieving a contrast of ≈ 10-6 within ≈ 0.8arcsec from the star while maintaining basically the normal sensitivity of VISIR. This should allow to detect a planet twice the diameter of Earth. Key components will be a diffractive coronagraphic mask, the annular groove phase mask (AGPM), optimized for the most sensitive spectral band-pass in the N-band, complemented by a sophisticated apodizer at the level of the Lyot stop. For VISIR noise filtering based on fast chopping is required. A novel internal chopper system will be integrated into the cryostat. This chopper is based on the standard technique from early radio astronomy, conceived by the microwave pioneer Robert Dicke in 1946, which was instrumental for the discovery of the 3K radio background.
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.
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.
Lightweight X-ray Wolter optics with a high angular resolution will enable the next generation of X-ray telescopes in space. The candidate mission ATHENA (Advanced Telescope for High Energy Astrophysics) required a mirror assembly of 1 m2 effective area (at 1 keV) and an angular resolution of 10 arcsec or better. These specifications can only be achieved with a novel technology like Silicon Pore Optics, which is being developed by ESA together with a consortium of European industry. Silicon Pore Optics are made of commercial Si wafers using process technology adapted from the semiconductor industry. We present the recent upgrades made to the manufacturing processes and equipment, ranging from the manufacture of single mirror plates towards complete focusing mirror modules mounted in flight configuration, and results from first vibration tests. The performance of the mirror modules is tested at X-ray facilities that were recently extended to measure optics at a focal distance up to 20 m.
Silicon Pore Optics (SPO) are the enabling technology for ESA’s second large class mission in the Cosmic Vision programme. As for every space hardware, a critical qualification process is required to verify the suitability of the SPO mirror modules surviving the launch loads and maintaining their performance in the space environment. We present recent design modifications to further strengthen the mounting system (brackets and dowel pins) against mechanical loads. The progress of a formal qualification test campaign with the new mirror module design is shown. We discuss mechanical and thermal limitations of the SPO technology and provide recommendations for the mission design of the next X-ray Space Observatory.
With the selection of “The hot and energetic Universe” as science theme for ESA's second large class mission (L2) in the Cosmic Vision programme, work is focusing on the technology preparation for an advanced X-ray observatory. The core enabling technology for the high performance mirror is the Silicon Pore Optics (SPO) [1 to 23], a modular X-ray optics technology, which utilises processes and equipment developed for the semiconductor industry. The paper provides an overview of the programmatic background, the status of SPO technology and gives an outline of the development roadmap and activities undertaken and planned by ESA on optics, coatings [24 to 30] and test facilities [31, 33].
Silicon Pore Optics (SPO) provide a high angular resolution with a low areal density as required for future X-ray telescopes for high energy astrophysics. We present progress in two areas of ESA’s SPO development activities: Stray light baffling and environmental qualification.
Residual stray light originating from off-axis sources or the sky background can be blocked by placing suitable baffles in front of the mirror modules. We developed two different mechanical implementations. The first uses longer, tapered mirror plates which improve the stray light rejection without the need of mounting additional parts to the modules or the telescope. The second method is based on placing a sieve plate in front of the optics. We compare both methods in terms of baffling performance using ray-tracing simulations and present test results of prototype mirror modules.
Any optics for space telescopes needs to be compliant with the harsh conditions of the launch and in-orbit operation. We present new work in improving the mechanical and thermal ruggedness of SPO mirror modules and show recent results of qualification level tests, including tests of modules with externally mounted sieve plate baffles.
Future high energy astrophysics missions will require high performance novel X-ray optics to explore the Universe beyond the limits of the currently operating Chandra and Newton observatories. Innovative optics technologies are therefore being developed and matured by the European Space Agency (ESA) in collaboration with research institutions and industry, enabling leading-edge future science missions.
Silicon Pore Optics (SPO) [1 to 21] and Slumped Glass Optics (SGO) [22 to 29] are lightweight high performance X-ray optics technologies being developed in Europe, driven by applications in observatory class high energy astrophysics missions, aiming at angular resolutions of 5” and providing effective areas of one or more square meters at a few keV.
This paper reports on the development activities led by ESA, and the status of the SPO and SGO technologies, including progress on high performance multilayer reflective coatings [30 to 35]. In addition, the progress with the X-ray test facilities and associated beam-lines is discussed .
Due to the exposed location of the Wendelstein observatory on the steep summit of mount Wendelstein no road exists to
transport telescope components and heavy equipment to the observatory in order to install the new 2m Fraunhofer
Telescope Wendelstein (FTW) in its new dome. A two step installation concept was therefore followed to mitigate any
risks that essential hardware would not work once installed on the mountain.
This paper reports on the telescope factory assembly and tests, including on-sky tests, which were performed in early
summer 2011 at the factory site to make sure, that the telescope and all essential subsystems are working properly before
the telescope would be installed on the mountain. The telescope was disassembled again to be transported to the
mountain in summer. Lifting of all structural subsystems and the optics up to the mountain observatory with the help of a
heavy lift helicopter will be presented in detail, also looking at specific design drivers, logistic aspects and special tools
for installation of the telescope and its mirrors in its new dome. Handling and transport concept for the M1 mirror
installation, which also will have to be used when the mirror is disassembled for recoating, are presented. Up to end of
2011 the telescope installation and pre-alignment could be completed including first on-sky tests. The system will
undergo a detailed performance test campaign in the first halve of 2012. Current performance results of these
commissioning activities will be reported.
Ludwig-Maximilians-Universitat Munchen operates an astrophysical observatory on the summit of Mt. Wendelstein1
which will be equipped with a modern 2m-class, robotic telescope. The plan is to operate one of the most
efficient robotic 2m telescopes in Europe in order to offer optimal scientific opportunities for our researchers
and maintain highest standards for the education of students. The 2m Fraunhofer telescope in its new 8.5m
dome has a modern, very compact alt.-azimuth design. Two Nasmyth ports will harbor a wide-field camera
(WWFI2), a medium field multi-channel camera (3kk3), a low resolution IFU spectrograph (VIRUSW4) and a
high resolution spectrograph (upgraded FOCES5). All instruments will be simultaneously ready for remote or
robotic observations. The telescope is designed as a 3-mirror f/7.8 system and should maintain the excellent
(< 0.8" median) seeing of the site1 over a field of view (f.o.v.) of 0.7 deg diameter with a field corrector for the
wide field port at optical wavelength. The second port provides a f.o.v. of 60 arcmin2 without any corrector
optics. It is optimized for simultaneous optical and NIR imaging as well as field spectroscopy and echelle high
resolution spectroscopy over the full optical wavelength regime.6 Here we present the design of the telescope as
well as the scope and projected time line of the overall project.
In this paper we present the latest developments on the ruggedisation of the Silicon Pore Optics (SPO) mirror
modules. SPO is one of the candidate technologies for producing the X-ray optics for the future space based Xray
telescope, the International X-ray Observatory (IXO). To produce SPO mirror modules, Si mirrors are first
bonded together using direct Si bonding to form a stack. These stacks are the glued into brackets, which then
connect to the supporting optical bench by invar pins. The combination of brackets and invar pins now forms a
full isostatic mount, and is rugged enough to allow the mirror module to survive the high loads of a launch. The
mounting system furthermore allows for a certain level of manufacturing tolerances for the support structure, and
ensures interchangeability of the mirror modules within one single ring of the optical bench. To prove this, a test
interface has been designed and manufactured, on which a single, full fledged mirror module will be mounted to
be exposed to environmental tests.
Ludwig-Maximilians-Universit¨at M¨unchen operates an astrophysical observatory on the summit of Mt. Wendelstein1
which will be equipped with a modern 2m-class, robotic telescope.2 One Nasmyth port of the new
Fraunhofer telescope is designed to sustain the excellent (< 0.8" median) seeing of the site [1, Fig. 1] over a FOV
of 0.2 deg2 utilizing three-element transmissive field corrector optics for optical wavebands. It will be equipped
with a camera built around a customized 64 MPixel Mosaic (Spectral Instruments, 4 × (4k)2 15μm e2v CCDs).
TheWendelsteinWide Field Imager has two filter wheels with eight slots each (SDSS3 [ugriz] + eight still free)
as well as two off-axis guiding units (two FLI Microline with 2k Fairchild CCDs on differential focus stages). A
Bonn Shutter4 ensures high precision photometric exposures. An option to either insert a low dispersion grating
(for field spectroscopy) or support a wave front sensor probe allows for further expansion of the camera. EMI-safe
housing has to overcome the emission of a close by 0.5MW radio station. Special care has been taken to design
a very low ghost budget of the overall system to allow for low-surface brightness applications (e.g. weak lensing
X-rays at various energies can be focussed with reflective optics at grazing incidence with a well-known reflectivity
achieving a high effective area by means of various designs. On XMM the high collecting area was achieved by means
of thin mirror shells which were made by nickel replication combining the parabola and hyperbola sections according to
the WOLTER I design in a single element. 58 of these "elements" were combined to build a mirror assembly with an
effective area of 1450 cm2 @1.5 keV per mirror assembly. In order to achieve a higher effective area for IXO the density
needs to be reduced. This could be achieved by pore optics elements integrated into a set of 8 petals made of Cesic® as
an optical bench. This design is fitting into the fairing of Ariane with a diameter of 4.2 m and achieves an effective area
of 3.36 m2. It will withstand the high launch loads of up to 60 g and provide a negligible degradation to the optical
performance due to thermal loads and gravitational relaxation. The design, including the interfaces to the telescope and
to the pore optics, will be presented.
MPE will provide the X-ray Survey Telescope eROSITA  for the Russian Spektrum-Roentgen-Gamma Mission  to
be launched in 2011. The design of the X-ray mirror system is based on that of ABRIXAS: The bundle of 7 mirror
modules with the short focal length of 1600 mm makes it still a compact instrument while, however, its sensitivity in
terms of effective area, field-of-view, and angular resolution shall be largely enhanced with respect to ABRIXAS. The
number of nested mirror shells increases from 27 to 54 compared to ABRIXAS thus enhancing the effective area in the
soft band by a factor of six. The angular resolution is targeted to be 15 arc seconds half-energy width (HEW) on-axis
resulting in an average HEW of 26 arc seconds over the 61 arc minutes field-of-view (FoV). The instrument's high grasp
of about 1000 cm2deg2 in the soft spectral range and still 10 cm2deg2 at 10 keV combined with a survey duration of 4
years will generate a new rich database of X-ray sources over the whole sky. As the 7 mirror modules are co-aligned
eROSITA is also able to perform pointed observations.
The PANTER X-ray Test Facility was originally designed to support the development and construction of the
ROSAT mirror system. A large instrument chamber (length 12 m, diameter 3.5m) accommodates the optics
to be analysed. The X-ray sources covering an 0.2 - 50 keV energy range are located at a distance of 123m
from the entrance to the chamber to provide an almost parallel X-ray beam. Both are connected by a vacuum
tube of 1m diameter. In addition to ROSAT a large number of astronomical systems like telescopes for Exosat,
BeppoSAX, JET-X, ABRIXAS, XMM-Newton and Swift - but also gratings (e.g., LETG on Chandra), filters,
and focal plane detectors have been measured at the facility. As a "growing facility" we are currently planning to
apply changes to the facility layout to support measurements of instrumentation for future missions like XEUS.
Currently a parallel beam is set up using a spare CDS mirror ("Coronal Diagnostic Spectrometer", for the SOHO
mission) as condensor. Moreover, extensions to vacuum tube and instrument chamber are under consideration,
both to allow calibration of systems with focal lengths significantly longer than XMM-Newton. A new focal plane
camera using a CCD developed for the eROSITA mission will improve spatial and spectral resolution. Finally,
the energy coverage shall be extended to lower and to higher energies. Already with the present configuration
important issues like performance under low temperatures could be investigated.
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.
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 , 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.
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.
It has been demonstrated that silicon pore optics can serve as the new technology for building the next generation of X-ray
telescopes for astronomical missions. In order to build up an optic in Wolter-I configuration, the high performance
pore optics (HPO) have to be co-aligned and integrated into pairs, forming so-called X-ray optical units (XOU). The
stringent co-alignment requirements for a 50 m focal length telescope like XEUS (e.g. 1 arcsecond between parabolic
and hyperbolic HPO) demand holistic alignment concepts, which integrate the metrology, the fixation and the
performance verification. The application in space and the resulting thermal requirements in combination with launch
loads and other mechanical restrictions must also be considered. Finite element modelling of different fixation
mechanisms and XOU configurations allow one both to assess difficulties at an early stage and to validate solution
strategies. This paper reports on the concepts, which have been developed. The most promising candidate has been
selected to build a form fit function model. The experimental set-up to align the HPOs, the required metrology and first
results of the performance verification at test facilities will be shown and discussed.
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.
In the frame of the X-ray Multi Mirror Mission (XMM), the second European Space Agency (ESA) cornerstone project, in total five Flight Models of the Mirror Module have been built. The mirror Modules are the optical heart of the satellite. Each Mirror Module contains 58 x-ray optical quality MIrror Shells which have been produced and integrated by Media Lario. Each of these MIrror Modules has been tested in the Centre Spatial de Liege (CSL) FOCAL-X facility. The goal of these test was to measure the otpical performance of the Mirror Modules under simulated launch and in-orbit configurations, and to perform some calibration on the Mirror Modules. To achieve these goals, a full EUV collimated beam is used to assess the optical characteristic in a representative flight configuration. The x-ray performance is controlled by means of an x-ray pencil beam and an x-ray collimator. The pencil beam is used for the determination of the Mirror Shell position, wing scattering and x-ray reflectivity measurements, the later one for the effective area measurement over 1.5 to 8 keV energy range. This paper mainly deals with the latest results achieved on the Flight Model 4 Mirror Assembly and the fifth Flight Mirror Module. The first one is integrated on the spacecraft, the second has been built to serve as an additional spare flight MM of the highest quality and to further develop the mirror module production and measurement process. After the presentation of these test results, the lessons learned from the manufacturing and the testing of the mirrors will be presented.
An ion beam figuring facility is operational at the Centre Spatial de Liege since 1997. Its present capabilities are described. An extensive characterization program is running in order to determine the optimized parameters for various materials and operating conditions. In this frame, tests have been performed on a spherical gold-coated aluminum mirror plated in between the with nickel. The nickel plating was used to be super-polished to a BRDF of 1 10-4 at 1 deg at 10 micrometers wavelength. Micro-roughness and etching rate measurements were realized and influence of ion bombardment on the coating has been established after removal of the gold coating. The gold coating removal of the gold coating. The gold coating removing was performed by using the ion beam flux. Finally, the mirror has been figure from the original sphere to a parabola. Surface characteristics evolution is also described in terms of micro-roughness and surface error. An overview of the research and development programs related to this facility is given. Results of this technique and potential impact on optics fabrication are then briefly exposed.
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.
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
The design and the main features of the new double pendulum type
michelson interferometer (DPI) by Kayser-Threde are presented.
The advantages of this spectrometer in comparison to conventional Fourier spectrometers are discussed. The DPI is compact in
design, mobile, insensitive to vibrations and temperature changes and, thus, well adapted to field measurements. The spectrometer was applied to emission as well as immission measurements
of air pollutants. Several molecules could be identified and
their concentrations could be estimated. The detection limit of
the DPI yields 15 - 60 ppm depending on the analyzed gas for
emission measurements, 6 - 84 ppb for immission measurements.