The Imaging X-ray Polarimetry Explorer, a NASA small explorer mission, will be the first mission dedicated to x-ray polarimetry. The payload consists of three identical telescopes, each comprising a mirror module assembly (MMA) with a polarization-sensitive detector at its focus. We describe all aspects of the MMA, from initial optical and mechanical design considerations to meet program requirements through mirror shell fabrication, mirror shell integration and module assembly, environmental testing, x-ray calibration, and on-ground and on-orbit alignment.
Launched on 2021 December 9, the Imaging X-ray Polarimetry Explorer (IXPE) is a NASA Small Explorer Mission in collaboration with the Italian Space Agency (ASI). The mission will open a new window of investigation—imaging x-ray polarimetry. The observatory features three identical telescopes, each consisting of a mirror module assembly with a polarization-sensitive imaging x-ray detector at the focus. A coilable boom, deployed on orbit, provides the necessary 4-m focal length. The observatory utilizes a three-axis-stabilized spacecraft, which provides services such as power, attitude determination and control, commanding, and telemetry to the ground. During its 2-year baseline mission, IXPE will conduct precise polarimetry for samples of multiple categories of x-ray sources, with follow-on observations of selected targets.
Expected to launch in Fall 2021, the Imaging X-ray Polarimetry Explorer (IXPE) is a NASA Astrophysics Small Explorer Mission with significant contributions from the Italian space agency (ASI). Three identical x-ray telescopes combine to form the IXPE observatory. Each is comprised of a 4-m-focal length mirror module assembly (MMA, provided by NASA MSFC) that focuses x-rays onto a polarization-sensitive, imaging detector (contributed by ASI-funded institutions). This paper describes the now-completed assembly process for the 3 flight mirror modules and spare, and compares as-tested calibrated performance with as-built metrology data. Unexpected challenges and lessons-learned are also discussed.
Scheduled to launch in late 2021 the Imaging X-ray Polarimetry Explorer (IXPE) is a Small Explorer Mission designed to open up a new window of investigation -- X-ray polarimetry. The IXPE observatory features 3 identical telescope each consisting of a mirror module assembly with a polarization-sensitive imaging x-ray detector at its focus. An extending beam, deployed on orbit provides the necessary 4 m focal length. The payload sits atop a 3-axis stabilized spacecraft which among other things provides power, attitude determination and control, commanding, and telemetry to the ground. During its 2-year baseline mission, IXPE will conduct precise polarimetry for samples of multiple categories of x-ray sources, with follow-on observations of selected targets. IXPE is a partnership between NASA and the Italian Space Agency (ASI).
The Marshall 100-Meter X-ray Beamline is a world class facility utilized for testing X-ray and EUV optics and instrumentation. Also known as the Stray Light Test Facility, the beamline has been consequential in the calibration of flight missions such as ART-XC and IXPE. Additionally, the beamline is effectively used for APRA-funded projects and in MSFC own internal optic development campaigns. The Marshall 100-Meter X-ray Beamline a flexible and affordable facility that easily accommodates many of the astrophysical community’s needs. With its recent and upcoming improvements, the Marshall 100-Meter X-ray Beamline will continue to be a user-friendly calibration resource for decades to come.
Wolter-I Optics for SmallSat Astronomy Mission (WOSAM) are a highly adaptable option for SmallSat missions for a number of astronomical uses. These compact Wolter-I optics with focal lengths on the order of 0.5 - 1 m are able to fit within strict mass and volume constraints and can be designed to fit the scientific requirements of exoplanet, solar, and lunar missions. In order to maximize Effective Area the telescope’s collecting area, graze angle, and vignetting need to be balanced. These factors are primarily affected by the optics’ focal length, outer diameter, shell length, and shell spacing. We show the modeling results of three SmallSat missions, the SmallSat Exosphere Explorer of hot Jupiters (SEEJ), the SmallSat Solar Axion and Activity X-ray Imager (SSAXI), and the Lunar X-ray Imaging Spectrometer (LuXIS). These missions have a range of Effective Area, Energy band, and Field of View requirements that can all be met with WOSAM telescopes.
IXPE, the Imaging X-ray Polarimetry Explorer, is a NASA SMEX mission with an important contribution of ASI that will be launched with a Falcon 9 in 2021 and will reopen the window of X-ray polarimetry after more than 40 years. The payload features three identical telescopes each one hosting one light-weight X-ray mirror fabricated by MSFC and one detector unit with its in-orbit calibration system and the Gas Pixel Detector sensitive to imaging X-ray polarization fabricated by INAF/IAPS, INFN and OHB Italy. The focal length after boom deployment from ATK-Orbital is 4 m, while the spacecraft is being fabricated by Ball Aerospace. The sensitivity will be better than 5.5% in 300 ks for a 1E-11 erg/s/cm2 (half mCrab) in the energy band of 2-8 keV allowing for sensitive polarimetry of extended and point-like X-ray sources. The focal plane instrument is completed, calibrated and it is going to be delivered at MSFC. We will present the status of the mission at about one year from the launch.
The Focusing Optics X-ray Solar Imager (FOXSI) sounding rocket payload achieved its third successful flight on September 7, 2018. FOXSI uses glancing-incidence Wolter-I mirrors combined with fine-pitch Si and CdTe detectors to perform direct solar Hard X-Ray (HXR) imaging spectroscopy. For FOXSI’s latest flight, several upgrades were made to the instrument, including updating the optics and detectors as well as adding new honeycomb type collimators to reduce Ghost rays background. We provide an overview of these updates as well as a discussion of their measured performance.
Expected to launch in 2021 Spring, the Imaging X-ray Polarimetry Explorer (IXPE) is a NASA Astrophysics Small Explorer Mission with significant contributions from the Italian space agency (ASI). The IXPE observatory features three identical x-ray telescopes, each comprised of a 4-m-focal length mirror module assembly (MMA, provided by MSFC) that focuses x-rays onto a polarization-sensitive, imaging detector (contributed by ASI-funded institutions). This paper summarizes the MMA’s design, fabrication, alignment and assembly, expected performance, and calibration plans.
Axion is a promising dark matter candidate as well as a solution to the strong charge-parity (CP) problem in quantum chromodynamics (QCD). We describe a new concept for SmallSat Solar Axion and Activity X-ray Telescope (SSAXI) to search for solar axions or axion-like particles (ALPs) and to monitor solar activity over a wide dynamic range. SSAXI aims to unambiguously identify X-rays converted from axions in the solar magnetic field along the line of sight to the solar core, effectively imaging the solar core. SSAXI employs Miniature lightweight Wolter-I focusing X-ray optics (MiXO) and monolithic CMOS X-ray sensors in a compact package. The wide energy range (0.5 - 5 keV) of SSAXI can easily distinguish spectra of axion-converted X-rays from solar X-ray spectra, while encompassing the prime energy band (3 - 4.5 keV) of axion-converted X-rays. The high angular resolution (30 arcsec) and large field of view (40 arcmin) in SSAXI will easily resolve the enhanced X-ray flux over the 3 arcmin wide solar core while fully covering the X-ray activity over the entire solar disc. The fast readout in the inherently radiation tolerant CMOS X-ray sensors enables high resolution spectroscopy over a wide dynamic range with a broad range of operational temperatures. We present multiple mission implementation options for SSAXI under ESPA class. SSAXI will operate in a Sun-synchronous orbit for 1 yr preferably near a solar minimum to accumulate sufficient X-ray photon statistics.
The Imaging X-ray Polarimetry Explorer (IXPE) will add polarization to the properties (time, energy, and position) observed in x-ray astronomy. A NASA Astrophysics Small Explorer (SMEX) in partnership with the Italian Space Agency (ASI), IXPE will measure the 2–8-keV polarization of a few dozen sources during the first 2 years following its 2021 launch. The IXPE Observatory includes three identical x-ray telescopes, each comprising a 4-m-focal-length (grazingincidence) mirror module assembly (MMA) and a polarization-sensitive (imaging) detector unit (DU), separated by a deployable optical bench. The Observatory’s Spacecraft provides typical subsystems (mechanical, structural, thermal, power, electrical, telecommunications, etc.), an attitude determination and control subsystem for 3-axis stabilized pointing, and a command and data handling subsystem communicating with the science instrument and the Spacecraft subsystems.
Lynx, one of the four strategic mission concepts under study for the 2020 Astrophysics Decadal Survey, provides leaps in capability over previous and planned x-ray missions and provides synergistic observations in the 2030s to a multitude of space- and ground-based observatories across all wavelengths. Lynx provides orders of magnitude improvement in sensitivity, on-axis subarcsecond imaging with arcsecond angular resolution over a large field of view, and high-resolution spectroscopy for point-like and extended sources in the 0.2- to 10-keV range. The Lynx architecture enables a broad range of unique and compelling science to be carried out mainly through a General Observer Program. This program is envisioned to include detecting the very first seed black holes, revealing the high-energy drivers of galaxy formation and evolution, and characterizing the mechanisms that govern stellar evolution and stellar ecosystems. The Lynx optics and science instruments are carefully designed to optimize the science capability and, when combined, form an exciting architecture that utilizes relatively mature technologies for a cost that is compatible with the projected NASA Astrophysics budget.
Lynx is the future x-ray observatory with superb imaging capabilities (<1 arc sec half-energy width) and large throughput (2 m2 effective area @ 1 keV), which is being considered in the U.S. to take over Chandra. The implementation of the x-ray mirror module represents a very challenging aspect, and different approaches are being considered. Thin and low-weight substrates, working in grazing incidence configuration, are necessary to meet the severe mass constraints, but they have to also preserve the requirement of an excellent angular resolution. The use of monolithic glass (fused silica) shells is an attractive solution, provided that their thickness is kept very small [<4 mm for mirror shells up of 3-m diameter]. We present the optomechanical design of the Lynx mirror assembly based on this approach, together with the ongoing technological development process. In particular, we discuss the figuring process, which is based on direct polishing followed by an ion-beam figuring correction. A temporary structure is specifically devoted to support the shell during the figuring and polishing operations and to manage the handling of the shell through all phases up to integration into the final telescope supporting spoke wheel. The results achieved so far on a prototype shell will be discussed.
NASA’s Marshall Space Flight Center (MSFC) maintains an active research program toward the development of high-resolution, lightweight, grazing-incidence x-ray optics to serve the needs of future x-ray astronomy missions such as Lynx. MSFC development efforts include both direct fabrication (diamond turning and deterministic computer-controlled polishing) of mirror shells and replication of mirror shells (from figured, polished mandrels). Both techniques produce full-circumference monolithic (primary + secondary) shells that share the advantages of inherent stability, ease of assembly, and low production cost. However, to achieve high-angular resolution, MSFC is exploring significant technology advances needed to control sources of figure error including fabrication- and coating-induced stresses and mounting-induced distortions.
Lynx is an X-ray mission concept with superb imaging capabilities (< 1arcsec Half Energy Width, HEW) and large throughput (2 m2 effective area @1keV). Several approaches are being considered to meet the challenging technological task of the mirror fabrication. Thin and light substrates are necessary to meet mass constraints. Monolithic fused silica shells are a possible solution if their thickness can be maintained to below 4 mm for mirror shells up to 3 m diameter. In this paper we present the opto-mechanical design of the mirror assembly, the technological processes, and the results achieved so far on a prototypal shells under development. In particular, emphasis is placed on the figuring process that is based on direct polishing and on ion beam figuring and on a temporary stiffening structure designed to support the shell during the figuring and polishing operations and to manage the handling of the shell through all phases up to integration into the telescope supporting structure.
The Imaging X-ray Polarimetry Explorer (IXPE) will expand the information space for study of cosmic sources, by adding polarization to the properties (time, energy, and position) observed in x-ray astronomy. Selected in 2017 January as a NASA Astrophysics Small Explorer (SMEX) mission, IXPE will be launched into an equatorial orbit in 2021. The IXPE observatory includes three identical x-ray telescopes, each comprising a 4-m-focal-length (grazing-incidence) mirror module assembly (MMA) and a polarization-sensitive (imaging) detector unit (DU). The optical bench separating the MMAs from the DUs is a deployable boom with a tip/tilt/rotation stage for DU-to-MMA (gang) alignment, similar to the configuration used for the NuSTAR observatory. The IXPE mission will provide scientifically meaningful measurements of the x-ray polarization of a few dozen sources in the 2-8 keV band, over the first two years of the mission. For several bright, extended x-ray sources (pulsar wind nebulae, supernova remnants, and an active-galaxy jet), IXPE observations will produce polarization maps indicating the magnetic structure of the synchrotron emitting regions. For many bright pulsating x-ray sources (isolated pulsars, accreting x-ray pulsars, and magnetars), IXPE observations will produce phase-resolved profiles of the polarization degree and position angle.
Lynx is a concept under study for prioritization in the 2020 Astrophysics Decadal Survey. Providing orders of magnitude increase in sensitivity over Chandra, Lynx will examine the first black holes and their galaxies, map the large-scale structure and galactic halos, and shed new light on the environments of young stars and their planetary systems. In order to meet the Lynx science goals, the telescope consists of a high-angular resolution optical assembly complemented by an instrument suite that may include a High Definition X-ray Imager, X-ray Microcalorimeter and an X-ray Grating Spectrometer. The telescope is integrated onto the spacecraft to form a comprehensive observatory concept. Progress on the formulation of the Lynx telescope and observatory configuration is reported in this paper.
Differential deposition, a post-fabrication figure correction technique, has the potential to significantly improve the imaging quality of grazing-incidence X-ray optics. DC magnetron sputtering is used to selectively coat the mirror in order to minimize the figure deviations. Custom vacuum chambers have been developed at NASA MSFC that will enable the implementation of the deposition on X-ray optics. A factor of two improvement has been achieved in the angular resolution of the full-shell X-ray optics with first stage correction of differential deposition. Current efforts are focused on achieving higher improvements through efficient implementation of differential deposition.
We have developed a process for indirectly coating arbitrarily small diameter electroformed nickel replicated optics with multilayers to increase their response at high energy (i.e. >10 keV). The ability to fabricate small diameter multilayer coated full shell Wolter X-ray optics with narrow bandpass opens the door to several applications within astronomy and also provides a path for cross-fertilization to other fields. We report on the characterization and evaluation of the first two prototype X-ray Wolter optics to be delivered to the Z Pulsed Power Facility at Sandia National Laboratories. The intent is to develop and field several optics as part of an imaging system with targeted spectral ranges.
In order to advance significantly scientific objectives, future x-ray astronomy missions will likely call for x-ray telescopes
with large aperture areas (≈ 3 m2) and fine angular resolution (≈ 12). Achieving such performance is programmatically
and technologically challenging due to the mass and envelope constraints of space-borne telescopes and to the need for
densely nested grazing-incidence optics. Such an x-ray telescope will require precision fabrication, alignment, mounting,
and assembly of large areas (≈ 600 m2) of lightweight (≈ 2 kg/m2 areal density) high-quality mirrors, at an acceptable cost
(≈ 1 M$/m2 of mirror surface area). This paper reviews relevant programmatic and technological issues, as well as possible
approaches for addressing these issues-including direct fabrication of monocrystalline silicon mirrors, active (in-space
adjustable) figure correction of replicated mirrors, static post-fabrication correction using ion implantation, differential
erosion or deposition, and coating-stress manipulation of thin substrates.
Spectrum Roentgen Gamma (SRG) is an X-ray astrophysical observatory, developed by Russia in collaboration with Germany. The mission will be launched in 2017 from Baikonur and placed in a 6-month-period halo orbit around L2. The scientific payload consists of two independent telescope arrays – a soft-x-ray survey instrument, eROSITA, being provided by Germany and a medium-x-ray-energy survey instrument ART-XC being developed by Russia. ART-XC will consist of seven independent, but co-aligned, telescope modules. The ART-XC flight mirror modules have been developed and fabricated at the NASA Marshall Space Flight Center (MSFC). Each mirror module will be aligned with a focal plane CdTe double-sided strip detector which will operate over the energy range of 6−30 keV, with an angular resolution of <1′, a field of view of ~34′ and an expected energy resolution of about 12% at 14 keV. The current status of the ART-XC/SRG instrument is presented here.
One of the challenges faced within the astronomical X-ray community is how to produce lightweight high angular resolution optics for a future X-ray mission capable of probing the early X-ray universe. To this end, the differential deposition project at NASA Marshall Space flight Center (MSFC) is looking to improve current X-ray optic technology by applying a corrective coating with a goal of achieving arc-second-level resolution. This paper will focus on the correction of segmented glass optics fabricated at NASA Goddard Space Flight Center (GSFC) and the paper will highlight: the design of the vacuum chamber and internal mechanics; the algorithm used to perform the correction; metrology of the glass segments; and the improvement post correction that has been achieved to date.
One of the developments at MSFC that is underway to meet the demand of high-resolution X-ray optics for future X-ray astronomy missions is the ‘differential deposition’ technique. This process corrects the axial figure profile of optics by selectively depositing material onto the mirror’s reflective surface. The process relies on accurate metrology achieved using a long trace profiler whose slope resolution is better than 1μrad. From these metrology data an error map is generated that shows the profile of material to be deposited to correct the optic’s figure. A computer-controlled, deposition system then applies this corrective coating.
Simulations show that a substantial improvement in angular resolution is possible with this approach after multiple correction ‘cycles’. To assess this, custom coating systems have been developed and corrections of full-shell optics are underway. To date, a factor of < 2 improvement in the imaging quality of the optics has been demonstrated in x-ray tests after a single stage of correction.
Spectrum Roentgen Gamma (SRG) is an X-ray astrophysical observatory, developed by Russia in collaboration with Germany. The mission will be launched in beginning 2017 from Baikonur and placed in a 6-month-period halo orbit around L2. The scientific payload consists of two independent telescopes – a soft-x-ray survey instrument, eROSITA, being provided by Germany and a medium-x-ray-energy survey instrument ART-XC being developed by Russia. ART-XC will consist of seven independent, but co-aligned, telescope modules. The ART-XC flight mirror modules has been developed and fabricated at the NASA Marshall Space Flight Center (MSFC). Each mirror module will be aligned with a focal plane CdTe double-sided strip detector which will operate over the energy range of 6−30 keV, with an angular resolution of <1′, a field of view of ~34′ and an expected energy resolution of about 12% at 14 keV. The current status of the ART-XC/SRG instrument will be present.
NASA's Marshall Space Flight Center (MSFC) engages in research, development, design, fabrication, coating, assembly, and testing of grazing-incidence optics (primarily) for x-ray telescope systems. Over the past two decades, MSFC has refined processes for electroformed-nickel replication of grazing-incidence optics, in order to produce highstrength, thin-walled, full-cylinder x-ray mirrors. In recent years, MSFC has used this technology to fabricate numerous x-ray mirror assemblies for several flight (balloon, rocket, and satellite) programs. Additionally, MSFC has demonstrated the suitability of this technology for ground-based laboratory applications—namely, x-ray microscopes and cold-neutron microscopes and concentrators. This mature technology enables the production, at moderately low cost, of reasonably lightweight x-ray telescopes with good (15–30 arcsecond) angular resolution. However, achieving arcsecond imaging for a lightweight x-ray telescope likely requires development of other technologies. Accordingly, MSFC is conducting a multi-faceted research program toward enabling cost-effective production of lightweight high-resolution x-ray mirror assemblies. Relevant research topics currently under investigation include differential deposition for post-fabrication figure correction, in-situ monitoring and control of coating stress, and direct fabrication of thin-walled full-cylinder grazing-incidence mirrors.
The future of x-ray astronomy depends upon development of x-ray telescopes with larger aperture areas (≈ 3 m2) and
fine angular resolution (≈ 1″). Combined with the special requirements of nested grazing-incidence optics, the mass and
envelope constraints of space-borne telescopes render such advances technologically and programmatically challenging.
Achieving this goal will require precision fabrication, alignment, mounting, and assembly of large areas (≈ 600 m2) of
lightweight (≈ 1 kg/m2 areal density) high-quality mirrors at an acceptable cost (≈ 1 M$/m2 of mirror surface area). This
paper reviews relevant technological and programmatic issues, as well as possible approaches for addressing these
issues—including active (in-space adjustable) alignment and figure correction.
The Astronomical Roentgen Telescope (ART) instrument is a hard-x-ray instrument with energy response up to 30 keV that is to be launched on board of the Spectrum Roentgen Gamma (SRG) Mission. The instrument consists of seven identical mirror modules coupled with seven CdTe strip focal-plane detectors. The mirror modules are being developed at the Marshall Space Flight Center (MSFC.) Each module has ~65 sq. cm effective area and an on-axis angular resolution of 30 arcseconds half power diameter (HPD) at 8 keV. The current status of the mirror module development and testing will be presented.
SuperHERO is a new high-resolution, Long Duration Balloon-capable, hard-x-ray (20-75 keV) focusing telescope for making novel astrophysics and heliophysics observations. The SuperHERO payload, currently in its proposal phase, is being developed jointly by the Astrophysics Office at NASA Marshall Space Flight Center and the Solar Physics Laboratory and the Wallops Flight Facility at NASA Goddard Space Flight Center. SuperHERO is a follow-on payload to the High Energy Replicated Optics to Explore the Sun (HEROES) balloon-borne telescope that recently flew from Fort Sumner, NM in September of 2013, and will utilize many of the same features. Significant enhancements to the HEROES payload will be made, including the addition of optics, novel solid-state multi-pixel CdTe detectors, integration of the Wallops Arc-Second Pointer and a significantly lighter gondola suitable for Long Duration Flights.
NASA’S future X-ray astronomy missions will require X-ray optics that have large effective area while remaining lightweight, and cost effective. Some X-ray missions, such as XMM-Newton[1] , and the upcoming Spectrum-Röntgen- Gamma[2] mission use an electroformed nickel replication (ENR) process[3] to fabricate the nested grazing incidence X-ray telescope mirror shells for an array of moderate resolution, moderate effective area telescopes. We are developing a process to fabricate metal-ceramic replicated optics which will be lighter weight than current nickel replicated technology. Our technology development takes full advantage of the replication technique by fabricating large diameter mirrors with thin cross sections allowing maximum nesting and increase in collecting area. This will lead to future cost effective missions with large effective area and lightweight optics with good angular resolution. Recent results on fabrication and testing of these optics is presented.
Spectrum Roentgen Gamma (SRG) is an X-ray astrophysical observatory, developed by Russia in collaboration with Germany. The mission will be launched in March 2016 from Baikonur, by a Zenit rocket with a Fregat booster and placed in a 6-month-period halo orbit around L2. The scientific payload consists of two independent telescopes – a softx- ray survey instrument, eROSITA, being provided by Germany and a medium-x-ray-energy survey instrument ART-XC being developed by Russia. ART-XC will consist of seven independent, but co-aligned, telescope modules. The NASA Marshall Space Flight Center (MSFC) is fabricating the flight mirror modules for the ART-XC/SRG. Each mirror module will be aligned with a focal plane CdTe double-sided strip detector which will operate over the energy range of 6−30 keV, with an angular resolution of <1′, a field of view of ~34′ and an expected energy resolution of about 10% at 14 keV.
The multi-beam long trace profiler (MB-LTP) is under development at NASA’s Marshall Space Flight Center. The
traditional LTPs scans the surface under the test by a single laser beam directly measuring the surface figure slope
errors. While capable of exceptional surface slope accuracy, the LTP single beam scanning has slow measuring
speed. Metrology efficiency can be increased by replacing the single laser beam with multiple beams that can scan a
section of the test surface at a single instance. The increase in speed with such a system would be almost
proportional to the number of laser beams. The progress for a multi-beam long trace profiler development is
presented.
The Marshall Space Flight Center (MSFC) is developing x-ray mirror modules for the ART-XC instrument on board the Spectrum-Roentgen Gamma Mission. Four of those modules are being fabricated under a Reimbursable Agreement between NASA and the Russian Space Research Institute (IKI.) An additional three flight modules and one spare for the ART-XC Instrument are produced under a Cooperative Agreement between NASA and IKI. The instrument will consist of seven co-aligned x-ray mirror modules with seven corresponding CdTe focal plane detectors. Each module consists of 28 nested thin Ni/Co shells giving an effective area of 65 cm2 at 8 keV, response out to 30 keV, and an angular resolution of 45 arcsec or better HPD. Delivery of the first four modules is scheduled for November 2013, while the remaining three modules will be delivered to IKI in January 2014. We present a status of the ART x-ray module development at MSFC.
NASA's Marshall Space Flight Center (MSFC) has a successful history of fabricating optics for astronomical x-ray telescopes. In recent years optics have been created using electroforming replication for missions such as the balloon payload HERO (High energy replicated optics) and the rocket payload FOXSI (Focusing Optics x-ray Solar Imager). The same replication process is currently being used in the creation seven x-ray mirror modules (one module comprising of 28 nested shells) for the Russian ART-XC (Astronomical Rontgen Telescope) instrument aboard the Spectrum-Roentgen-Gamma mission and for large-diameter mirror shells for the Micro-X rocket payload.
In addition to MSFC's optics fabrication, there are also several areas of research and development to create the high resolution light weight optics which are required by future x-ray telescopes. Differential deposition is one technique which aims to improve the angular resolution of lightweight optics through depositing a filler material to smooth out fabrication imperfections. Following on from proof of concept studies, two new purpose built coating chambers are being assembled to apply this deposition technique to astronomical x-ray optics. Furthermore, MSFC aims to broaden its optics fabrication through the recent acquisition of a Zeeko IRP 600 robotic polishing machine. This paper will provide a summary of the current missions and research and development being undertaken at NASA's MSFC.
The multi-beam long trace profiler (LTP) under development at NASA’s Marshall Space Flight Center[1] is designed to increase the efficiency of metrology of replicated X-ray optics. The traditional LTP operates on a single laser beam that scans along the test surface to detect the slope errors. While capable of exceptional surface slope accuracy, the LTP single beam scanning has slow measuring speed. As metrology constitutes a significant fraction of the time spent in optics production, an increase in the efficiency of metrology helps in decreasing the cost of fabrication of the x-ray optics and in improving their quality. Metrology efficiency can be increased by replacing the single laser beam with multiple beams that can scan a section of the test surface at a single instance. The increase in speed with such a system would be almost proportional to the number of laser beams. A collaborative feasibility study has been made and specifications were fixed for a multi-beam long trace profiler. The progress made in the development of this metrology system is presented.
Spectrum Roentgen Gamma (SRG) is an X-ray astrophysical observatory, developed by Russia in collaboration with Germany. The mission will be launched in 2014 from Baikonur, by a Zenit rocket with a Fregat booster and placed in a 6-month-period halo orbit around L2. The scientific payload consists of two independent telescopes – a soft-x-ray survey instrument, eROSITA, being provided by Germany and a medium-x-ray-energy survey instrument ART-XC being developed by Russia. ART-XC will consist of seven independent, but co-aligned, telescope modules with seven corresponding cadmium-telluride focal plane detectors. Each will operate over the approximate energy range of 6−30 keV, with an angular resolution of <1′, a field of view of ~30' and an energy resolution about 10% at 14 keV. The NASA Marshall Space Flight Center (MSFC) will fabricate some of the mirror modules, to complement others fabricated by VNIIEF in Russia.
The Marshall Space Flight Center (MSFC) is developing x-ray mirror modules for the ART-XC instrument on board the Spectrum-Roentgen-Gamma Mission under a Reimbursable Agreement between NASA and the Russian Space Research Institute (IKI.) ART-XC will consist of seven co-aligned x-ray mirror modules with seven corresponding CdTe focal plane detectors. Currently, four of the modules are being fabricated by the Marshall Space Flight Center (MSFC.) Each MSFC module consist of 28 nested Ni/Co thin shells giving an effective area of 65 cm2 at 8 keV, response out to 30 keV, and an angular resolution of 45 arcsec or better HPD. Delivery of these modules to the IKI is scheduled for summer 2013. We present a status of the ART x-ray modules development at the MSFC.
A coating technique is being developed to correct the surface figure deviations in grazing-incidence X-ray
optics. These optics are typically designed to have precise conic profiles, and any deviation in this profile, as a result of
fabrication, results in a degradation of the imaging performance. To correct the mirror profiles, physical vapor
deposition has been utilized to selectively deposit a filler material inside the mirror shell. The technique, termed
differential deposition, has been implemented as a proof of concept on miniature X-ray optics developed at MSFC for
medical-imaging applications. The technique is now being transferred to larger grazing-incidence optics suitable for
astronomy.
In order to fulfill the angular resolution requirements and make the performance goals for future NASA missions
feasible, it is crucial to develop instruments capable of fast and precise figure metrology of x-ray optical elements for
further correction of the surface errors. The Long Trace Profilometer (LTP) is an instrument widely used for measuring
the surface figure of grazing incidence X-ray mirrors. In the case of replicated optics designed for x-ray astronomy
applications, such as mirrors and the corresponding mandrels have a cylindrical shape and their tangential profile is
parabolic or hyperbolic. Modern LTPs have sub-micro radian accuracy, but the measuring speed is very low, because
the profilometer measures surface figure point by point using a single laser beam. The measurement rate can be
significantly improved by replacing the single optical beam with multiple beams. The goal of this study is to
demonstrate the viability of multi-beam metrology as a way of significantly improving the quality and affordability of
replicated x-ray optics. The multi-beam LTP would allow one- and two-dimensional scanning with sub-micro radian
resolution and a measurement rate of about ten times faster compared to the current LTP. The design details of the
instrument's optical layout and the status of optical tests will be presented.
Spectrum Roentgen Gamma (SRG) is an X-ray astrophysical observatory, developed by Russia in collaboration with
Germany. The mission will be launched in 2013 from Baikonur, by a Zenit rocket with a Fregat booster and placed in a
6-month-period halo orbit around L2. The scientific payload consists of two independent telescopes - a soft-x-ray survey
instrument, eROSITA, being provided by Germany and a medium-x-ray-energy survey instrument ART-XC being
developed by Russia.
ART-XC will consist of seven independent, but co-aligned, telescope modules with seven corresponding cadmiumtelluride
focal plane detectors. Each will operate over the approximate energy range of 6-30 keV, with an angular
resolution of 1 arcmin, a field of view of ~30 arcmin and an energy resolution about 10% at 14 keV. The NASA
Marshall Space Flight Center (MSFC) will fabricate some of the mirror modules, to complement others fabricated by
VNIIEF in Russia.
A differential deposition technique was investigated as a way to minimize axial figure errors in full-shell, grazing-incidence, reflective x-ray optics. These types of optics use a combination of off-axis conic segments-hyperbolic, parabolic, and/or elliptical, to reflect and image x-rays. Several such mirrors or "shells" of decreasing diameter are typically concentrically nested to form a single focusing unit. Individual mirrors are currently produced at Marshall Space Flight Center using an electroforming technique, in which the shells are replicated off figured and superpolished mandrels. Several factors in this fabrication process lead to low- and mid-spatial frequency deviations in the surface profile of the shell that degrade the imaging quality of the optics. A differential deposition technique, discussed in this paper, seeks to improve the achievable resolution of the optics by correcting the surface profile deviations of the shells after fabrication. As a proof of concept, the technique was implemented on small-animal radionuclide-imaging x-ray optics being considered for medical applications. This paper discusses the deposition technique, its implementation, and the experimental results obtained to date.
In the case of neutrons the refractive index is slightly less than unity for most elements and their isotopes [1].
Consequently, thermal and cold neutrons can be reflected from smooth surfaces at grazing-incidence angles. Hence, the
optical technologies developed for x-ray astronomy can be applied for neutron focusing. The focusing capabilities of
grazing incidence neutron imaging optics have been successfully demonstrated using nickel mirrors. The mirrors were
fabricated using an electroformed nickel replication process at Marshall Space Flight Center. Results of the neutron
optics experiments and current status of the multilayer coating replication technique development are presented.
A differential deposition technique is being developed to correct the low- and mid-spatial-frequency deviations in the
axial figure profile of Wolter-type grazing-incidence X-ray optics. These deviations arise due to various factors in the
fabrication process and they degrade the performance of optics by limiting the achievable angular resolution. In the
differential deposition technique, material is selectively deposited in varying thickness along the length of the optic to
minimize these deviations, thereby improving the overall figure.
The process is being tested on focusing X-ray optics being developed at MSFC for small-animal radionuclide imaging.
The required spatial resolution for these optics is 100 μm (30 arc secs), which can be achieved with the electroformnickel-
replication fabrication technique regularly employed at MSFC. However, by improving the figure quality of the
optics through differential deposition, we aim to significantly improve the resolution beyond this value.
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