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.
The European Space Agency (ESA) is studying the ATHENA (Advanced Telescope for High ENergy Astrophysics) X-ray telescope, the second L-class mission in their Cosmic Vision 2015 – 2025 program with a launch spot in 2028. The baseline technology for the X-ray lens is the newly developed high-performance, light-weight and modular Silicon Pore Optics (SPO). As part of the technology preparation, ruggedisation and environmental testing studies are being conducted to ensure mechanical stability and optical performance of the optics during and after launch, respectively. At cosine, a facility with shock, vibration, tensile strength, long time storage and thermal testing equipment has been set up in order to test SPO mirror module (MM) materials for compliance with an Ariane launch vehicle and the mission requirements. In this paper, we report on the progress of our ongoing investigations regarding tests on mechanical and thermal stability of MM components like single SPO stacks with and without multilayer coatings and complete MMs of inner (R = 250 mm), middle (R = 737 mm) and outer (R = 1500 mm) radii.
The work on the definition and technological preparation of the ATHENA (Advanced Telescope for High ENergy Astrophysics) mission continues to progress. In parallel to the study of the accommodation of the telescope, many aspects of the X-ray optics are being evolved further. The optics technology chosen for ATHENA is the Silicon Pore Optics (SPO), which hinges on technology spin-in from the semiconductor industry, and uses a modular approach to produce large effective area lightweight telescope optics with a good angular resolution. Both system studies and the technology developments are guided by ESA and implemented in industry, with participation of institutional partners. In this paper an overview of the current status of the telescope optics accommodation and technology development activities is provided.
Silicon Pore Optics (SPO), developed at cosine with the European Space Agency (ESA) and several academic and industrial partners, provides lightweight, yet stiff, high-resolution x-ray optics. This technology enables ATHENA to reach an unprecedentedly large effective area in the 0.2 - 12 keV band with an angular resolution better than 5''. After developing the technology for 50 m and 20 m focal length, this year has witnessed the first 12 m focal length mirror modules being produced. The technology development is also gaining momentum with three different radii under study: mirror modules for the inner radii (Rmin = 250 mm), outer radii (Rmax = 1500 mm) and middle radii (Rmid = 737 mm) are being developed in parallel.
Silicon Pore Optics is a high-energy optics technology, invented to enable the next generation of high-resolution,
large area X-ray telescopes such as the ATHENA observatory, a European large (L) class mission with a launch
date of 2028. The technology development is carried out by a consortium of industrial and academic partners and
focuses on building an optics with a focal length of 12 m that shall achieve an angular resolution better than 5”.
So far we have built optics with a focal length of 50 m and 20 m.
This paper presents details of the work carried out to build silicon stacks for a 12 m optics and to integrate them
into mirror modules. It will also present results of x-ray tests taking place at PTB’s XPBF with synchrotron
radiation and the PANTER test facility.
The Large Observatory For x-ray Timing (LOFT) is a mission concept which was proposed to ESA as M3 and M4 candidate in the framework of the Cosmic Vision 2015-2025 program. Thanks to the unprecedented combination of effective area and spectral resolution of its main instrument and the uniquely large field of view of its wide field monitor, LOFT will be able to study the behaviour of matter in extreme conditions such as the strong gravitational field in the innermost regions close to black holes and neutron stars and the supra-nuclear densities in the interiors of neutron stars. The science payload is based on a Large Area Detector (LAD, >8m2 effective area, 2-30 keV, 240 eV spectral resolution, 1 degree collimated field of view) and a Wide Field Monitor (WFM, 2-50 keV, 4 steradian field of view, 1 arcmin source location accuracy, 300 eV spectral resolution). The WFM is equipped with an on-board system for bright events (e.g., GRB) localization. The trigger time and position of these events are broadcast to the ground within 30 s from discovery. In this paper we present the current technical and programmatic status of the mission.
ATHENA (Advanced Telescope for High ENergy Astrophysics) is being studied by the European Space Agency (ESA) as the second large science mission, with a launch slot in 2028. System studies and technology preparation activities are on-going. The optics of the telescope is based on the modular Silicon Pore Optics (SPO), a novel X-ray optics technology significantly benefiting from spin-in from the semiconductor industry. Several technology development activities are being implemented by ESA in collaboration with European industry and institutions. The related programmatic background, technology development approach and the associated implementation planning are presented.
The Advanced Telescope for High ENergy Astrophysics (Athena) was selected in 2014 as the second large class mission (L2) of the ESA Cosmic Vision Science Programme within the Directorate of Science and Robotic Exploration. The mission development is proceeding via the implementation of the system studies and in parallel a comprehensive series of technology preparation activities. [1-3]. The core enabling technology for the high performance mirror is the Silicon Pore Optics (SPO), a modular X-ray optics technology, which utilises processes and equipment developed for the semiconductor industry [4-31]. This paper provides an overview of the programmatic background, the status of SPO technology and give an outline of the development roadmap and activities undertaken and planned by ESA.
Athena (Advanced Telescope for High Energy Astrophysics) is an x-ray observatory using a Silicon Pore Optics
telescope and was selected as ESA’s second L-class science mission for a launch in 2028. The x-ray telescope consists of
several hundreds of mirror modules distributed over about 15-20 radial rings. The radius of curvature and the module
sizes vary among the different radial positions of the rings resulting in different technical challenges for mirror modules
for inner and outer radii.
We present first results of demonstrating Silicon Pore Optics for the extreme radial positions of the Athena telescope.
For the inner most radii (0.25 m) a new mirror plate design is shown which overcomes the challenges of larger
curvatures, higher stress values and bigger plates. Preliminary designs for the mounting system and its mechanical
properties are discussed for mirror modules covering all other radial positions up to the most outer radius of the Athena
The ATHENA mission, a European large (L) class X-ray observatory to be launched in 2028, will essentially consist of an X-ray lens and two focal plane instruments. The lens, based on a Wolter-I type double reflection grazing incidence angle design, will be very large (~ 3 m in diameter) to meet the science requirements of large effective area (1-2 m2 at a few keV) at a focal length of 12 m. To meet the high angular resolution (5 arc seconds) requirement the X-ray lens will also need to be very accurate. Silicon Pore Optics (SPO) technology has been invented to enable building such a lens and thus enabling the ATHENA mission. We will report in this paper on the latest status of the development, including details of X-ray test campaigns.
The Large Observatory For x-ray Timing (LOFT) was studied within ESA M3 Cosmic Vision framework and participated in the final downselection for a launch slot in 2022-2024. Thanks to the unprecedented combination of effective area and spectral resolution of its main instrument, LOFT will study the behaviour of matter under extreme conditions, such as the strong gravitational field in the innermost regions of accretion flows close to black holes and neutron stars, and the supranuclear densities in the interior of neutron stars. The science payload is based on a Large Area Detector (LAD, 10 m2 effective area, 2-30 keV, 240 eV spectral resolution, 1° collimated field of view) and a Wide Field Monitor (WFM, 2-50 keV, 4 steradian field of view, 1 arcmin source location accuracy, 300 eV spectral resolution). The WFM is equipped with an on-board system for bright events (e.g. GRB) localization. The trigger time and position of these events are broadcast to the ground within 30 s from discovery. In this paper we present the status of the mission at the end of its Phase A study.
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, after 10 years of development, forms now the basis for future large (L) class astrophysics Xray observatories, such as the ATHENA mission to study the hot and energetic universe, matching the L2 science theme recently selected by ESA for launch in 2028. The scientific requirements result in an optical design that demands high angular resolution (5“) and large effective area (2 m2 at a few keV) of an X-ray lens with a focal length of 12 to14 m. Silicon Pore Optics was initially based on long (25 to 50 m) focal length telescope designs, which could achieve several arc second angular resolution by curving the silicon mirror in only one direction (conical approximation). With the advent of shorter focal length missions we started to develop mirrors having a secondary curvature, allowing the production of Wolter-I type optics, which are on axis aberration-free. In this paper we will present the new manufacturing process, discuss the impact of the ATHENA optics design on the technology development and present the results of the latest X-ray test campaigns.
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.
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 .
Silicon Pore Optics is an enabling technology for future L- and M-class astrophysics X-ray missions, which require high angular resolution (~5 arc seconds) and large effective area (1 to 2 m2 at a few keV). The technology exploits the high-quality of super-polished 300 mm silicon wafers and the associated industrial mass production processes, which are readily available in the semiconductor industry. The plan-parallel wafers have a surface roughness better than 0.1 nm rms and are diced, structured, wedged, coated, bent and stacked to form modular Silicon Pore Optics, which can be grouped into a larger optic. The modules are assembled from silicon alone, with all the mechanical advantages, and form an intrinsically stiff pore structure.
The optics design was initially based on long (25 to 50 m) focal length X-ray telescopes, which could achieve several arc second angular resolution by curving the silicon mirror in only one direction (conical approximation).
Recently shorter focal length missions (10 to 20 m) have been discussed, for which we started to develop Silicon Pore Optics having a secondary curvature in the mirror, allowing the production of Wolter-I type optics, which are on axis aberration-free.
In this paper we will present the new manufacturing process, the results achieved and the lessons learned.
Silicon Pore Optics (SPO) is a lightweight high performance X-ray optics technology being developed in Europe, driven by applications in observatory class high energy astrophysics missions. An example of such application is the former ESA science mission candidate ATHENA (Advanced Telescope for High Energy Astrophysics), which uses the SPO technology for its two telescopes, in order to provide an effective area exceeding 1 m2 at 1 keV, and 0.5 m2 at 6 keV, featuring an angular resolution of 10” or better [1 to 24].
This paper reports on the development activities led by ESA, and the status of the SPO technology. The technology development programme has succeeded in maturing the SPO further and achieving important milestones, in each of the main activity streams: environmental compatibility, industrial production and optical performance. In order to accurately characterise the increasing performance of this innovative optical technology, the associated X-ray test facilities and beam-lines have been refined and upgraded.
Silicon pore optics is a technology developed to enable future large area X-ray telescopes, such as the
International X-ray Observatory (IXO) or the Advanced Telescope for High ENergy Astrophysics (ATHENA),
an L-class candidate mission in the ESA Space Science Programme 'Cosmic Visions 2015-2025'.
ATHENA/IXO use nested mirrors in Wolter-I configuration to focus grazing incidence X-ray photons on a
detector plane. The x-ray optics will have to meet stringent performance requirements including an effective area
of a few m2 at 1.25 keV and angular resolution between 5(IXO) and 9(ATHENA) arc seconds. To achieve the
collecting area requires a total polished mirror surface area close to 1000 m2 with a surface roughness better than
0.5 nm rms. By using commercial high-quality 12" silicon wafers which are diced, structured, wedged, coated,
bent and stacked, the stringent performance requirements can be met without any costly polishing steps. Two of
such stacks are then assembled into a co-aligned mirror module, which is a complete X-ray imaging system.
Included in the mirror module are the isostatic mounting points, providing a reliable interface to the telescope.
Hundreds of such mirror modules are finally integrated into petals, and mounted onto the spacecraft to form an
X-ray optic. In this paper we will present the silicon pore optics mass manufacturing process and latest X-ray test
The International X-ray Observatory (IXO) is a candidate mission in the ESA Space Science Programme Cosmic Vision
1525, and was studied as a joint mission with NASA and JAXA. Considering the programmatic evolution of the
international context, the mission is being reformulated as an ESA-led mission, under the name of ATHENA (Advanced
Telescope for High Energy Astrophysics), with possible participation of NASA and JAXA.
The mission is building on the novel Silicon Pore Optics (SPO) technology to achieve the required performance for this
demanding astrophysics observatory. This technology is being developed by an industrial consortium, and involves also
several research institutes [1-12]. A second optics technology, slumped glass optics (SGO), which is being developed in
Europe and the USA, was the backup technology for IXO, and additionally work is progressing on improved reflective
coatings and X-ray test facilities [13-17].
The establishment of Silicon Pore Optics (SPO) as the technology of choice for the implementation of future large
X-ray space optics has opened up the road to its use in all classes of X-ray missions with varying scientific goals.
This interest has given us the possibility to broaden the design parameter space which is normally considered
for SPO optics. In doing so a number of classical space X-ray optics design issues (e.g., field of view, stray
light, baffling, aberrations) have been tackled. In this paper we report on recent results achieved in this effort.
Particular attention will be given to the issues of stray light and baffling, a topic upon which a combination of
analytical, simulation, and data analysis means can be effectively brought to bear. Missions considering the use
of SPO optics have requirements spanning more than two orders of magnitude in energy, and a factor 20 in focal
length. The possibilities that can be considered and the trade offs that must be made when applying SPO to
such a wide range of optical designs will be illustrated, and some of the possible solutions discussed.
ORIGIN is a medium size high-energy mission concept submitted to ESA in response to the Cosmic Vision call issued
on July 2010. The mission will investigate the evolution of the Universe by performing soft X-ray high resolution
spectroscopic measurements of metals formed in different astrophysical environments, from the first population III stars
at z > 7 to the present large scale structures. The main instrument on-board ORIGIN will be a large format array of TES
X-ray micro-calorimeters covering a FOV of 30' at the focal plane of a grazing incidence optical module with a focal
length of 2.5 m and an angular resolution of 30'' HEW at 1 keV. We present the optical module design which is based
on hybrid technologies, namely Silicon Pore Optics for the outer section and Ni electro-forming for the inner section,
and we present the expected performances based on test measurements and ray-tracing simulations.
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.
Silicon pore optics is a technology developed to enable future large area X-ray telescopes, such as the
International X-ray Observatory (IXO), a candidate mission in the ESA Space Science Programme 'Cosmic
Visions 2015-2025'. IXO uses nested mirrors in Wolter-I configuration to focus grazing incidence X-ray photons
on a detector plane. The IXO optics will have to meet stringent performance requirements including an effective
area of >2.5 m2 at 1.25 keV and >0.65 m2 at 6 keV and angular resolution better than 5 arc seconds. To achieve
the collecting area requires a total polished mirror surface area of ~1300 m2 with a surface roughness better than
0.5 nm rms. By using commercial high-quality 12" silicon wafers which are diced, structured, wedged, coated,
bent and stacked, the stringent performance requirements of IXO can be attained without any costly polishing
steps. Two of these stacks are then assembled into a co-aligned mirror module, which is a complete X-ray
imaging system. Included in the mirror module are the isostatic mounting points, providing a reliable interface to
the telescope. Hundreds of such mirror modules are finally integrated into petals, and mounted onto the
spacecraft to form an X-ray optic of approximately 4 m in diameter.
In this paper we will present the silicon pore optics mass manufacturing process and latest X-ray test results of
mirror modules mounted in flight configuration.
Spatially resolved X-ray spectroscopy with high spectral resolution allows the study of astrophysical processes in
extended sources with unprecedented sensitivity. This includes the measurement of abundances, temperatures, densities,
ionisation stages as well as turbulence and velocity structures in these sources. An X-ray calorimeter is planned for the
Russian mission Spektr Röntgen-Gamma (SRG), to be launched in 2011. During the first half year (pointed phase) it will
study the dynamics and composition of of the hot gas in massive clusters of galaxies and in supernova remnants (SNR).
During the survey phase it will produce the first all sky maps of line-rich spectra of the interstellar medium (ISM).
Spectral analysis will be feasible for typically every 5° x 5° region on the sky. Considering the very short time-scale for
the development of this instrument it consists of a combination of well developed systems. For the optics an extra
eROSITA mirror, also part of the Spektr-RG payload, will be used. The detector will be based on spare parts of the
detector flown on Suzaku combined with a rebuild of the electronics and the cooler will be based on the design for the
Japanese mission NeXT. In this paper we will present the science and give an overview of the instrument.
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.