The Origins Space Telescope (Origins) study team prepared and submitted a Mission Concept Study Report for the 2020 Decadal Survey in Astrophysics. During the study, a Materials Working Group was formed to evaluate materials for Origins. The Materials Working Group identified material candidates and evaluated the candidates using driving requirements and key material considerations. The evaluation resulted in several options to aid the study team in making a materials selection for the mission concept. Our paper details the approach to the materials evaluation and the results.
The Origins Space Telescope will trace the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life. How did galaxies evolve from the earliest galactic systems to those found in the Universe today? How do habitable planets form? How common are life-bearing worlds? To answer these alluring questions, Origins will operate at mid- and far-infrared (IR) wavelengths and offer powerful spectroscopic instruments and sensitivity three orders of magnitude better than that of the Herschel Space Observatory, the largest telescope flown in space to date. We describe the baseline concept for Origins recommended to the 2020 US Decadal Survey in Astronomy and Astrophysics. The baseline design includes a 5.9-m diameter telescope cryocooled to 4.5 K and equipped with three scientific instruments. A mid-infrared instrument (Mid-Infrared Spectrometer and Camera Transit spectrometer) will measure the spectra of transiting exoplanets in the 2.8 to 20 μm wavelength range and offer unprecedented spectrophotometric precision, enabling definitive exoplanet biosignature detections. The far-IR imager polarimeter will be able to survey thousands of square degrees with broadband imaging at 50 and 250 μm. The Origins Survey Spectrometer will cover wavelengths from 25 to 588 μm, making wide-area and deep spectroscopic surveys with spectral resolving power R ∼ 300, and pointed observations at R ∼ 40,000 and 300,000 with selectable instrument modes. Origins was designed to minimize complexity. The architecture is similar to that of the Spitzer Space Telescope and requires very few deployments after launch, while the cryothermal system design leverages James Webb Space Telescope technology and experience. A combination of current-state-of-the-art cryocoolers and next-generation detector technology will enable Origins’ natural background-limited sensitivity.
The Origins Space Telescope will trace the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life. How did galaxies evolve from the earliest galactic systems to those found in the universe today? How do habitable planets form? How common are life-bearing worlds? To answer these alluring questions, Origins will operate at mid- and far-infrared wavelengths and offer powerful spectroscopic instruments and sensitivity three orders of magnitude better than that of Herschel, the largest telescope flown in space to date. After a 3 ½ year study, the Origins Science and Technology Definition Team will recommend to the Decadal Survey a concept for Origins with a 5.9-m diameter telescope cryocooled to 4.5 K and equipped with three scientific instruments. A mid-infrared instrument (MISC-T) will measure the spectra of transiting exoplanets in the 2.8 – 20 μm wavelength range and offer unprecedented sensitivity, enabling definitive biosignature detections. The Far-IR Imager Polarimeter (FIP) will be able to survey thousands of square degrees with broadband imaging at 50 and 250 μm. The Origins Survey Spectrometer (OSS) will cover wavelengths from 25 – 588 μm, make wide-area and deep spectroscopic surveys with spectral resolving power R ~ 300, and pointed observations at R ~ 40,000 and 300,000 with selectable instrument modes. Origins was designed to minimize complexity. The telescope has a Spitzer-like architecture and requires very few deployments after launch. The cryo-thermal system design leverages JWST technology and experience. A combination of current-state-of-the-art cryocoolers and next-generation detector technology will enable Origins’ natural backgroundlimited sensitivity.
The Origins Space Telescope (OST) will trace the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life. How did the universe evolve in response to its changing ingredients? How common are life-bearing planets? To accomplish its scientific objectives, OST will operate at mid- and far-infrared wavelengths and offer superlative sensitivity and new spectroscopic capabilities. The OST study team will present a scientifically compelling, executable mission concept to the 2020 Decadal Survey in Astrophysics. To understand the concept solution space, our team studied two alternative mission concepts. We report on the study approach and describe both of these concepts, give the rationale for major design decisions, and briefly describe the mission-enabling technology.
NASA is exploring telescope and mirror technology options to meet the demanding science goals of the proposed HabEx space telescope. A key priority for the HabEx mission concept would be to leverage affordable telescope solutions that can meet challenging telescope performance requirements with a demanding program timeline. The baseline approach for HabEx is to use an unobscured, monolithic primary mirror with a coronagraph to optimize system performance. NASA is performing an initial study to investigate the feasibility of a HabEx Lite concept which would not leverage a coronagraph and would therefore, have lower exoEarth yield as a consequence, but could provide system mass, cost, and schedule advantages. The HabEx Lite concept leverages replicated, ULE® mirror segments to provide an attractive, alternative telescope architecture to meet the HabEx threshold mission needs. We present the initial mirror design and performance assessment for the HabEx Lite concept.
With more rapid, affordable access to space and the emerging availability of large-volume fairings, owners and users of current and future space-based optical systems are desiring large-aperture or segmented-aperture primary mirrors for their missions. This demand is driving the need for new approaches to optical component fabrication to produce mirrors and mirror segments that are more cost-efficient with faster manufacturing lead times than traditional optical components. Harris Corporation is executing a mirror development strategy called Advanced Mirror Construction (AMC) to meet this need while still meeting the challenging requirements of space-based optics. A key component of this strategy is the utilization of replication to produce precision lightweight mirror components. We present the motivation and initial results for lightweight replicated, ultra-stable mirrors and mirror segments as well as other key elements of the AMC strategy.
One of the flagship-class missions under study for the Astro 2020 Decadal review is the Lynx x-ray mission. It has significant design heritage to the highly successful Chandra X-ray Observatory. This report will highlight work done by the CAN Consortium of Northrop Grumman, Ball and Harris supporting the mission concept development led by the Lynx Science and Technology Definition Team (STDT) and MSFC Study Office. By comparing the Lynx requirements against the demonstrated performance of the Chandra Observatory, this paper will highlight the high TRL technologies that can be re-used from Chandra and those that will require new development , which impacts the Lynx architecture and development requirements. This paper will also summarize the top level performance budgets, performance predictions and suggestions on the calibration approach.
KEYWORDS: Mirrors, Adhesives, Wavefronts, 3D modeling, Control systems, Systems modeling, Thermal modeling, Temperature metrology, Coronagraphy, Metrology
For internal coronagraph options on the LUVOIR or HabEx mission concepts, the stated challenge of 10 picometers RMS wavefront stability over 10 minutes will govern the performance of every structure that connects the focal plane assembly to each optical surface. This paper interrogates wavefront stability of a mounted mirror assembly for a primary mirror segment assembly, and stability of the optical surface. Analysis describes stability of each element in a primary mirror segment assembly (PMSA) to understand the impact of each component of the PMSA on surface figure error (SFE) over short time periods.
Large visible telescopes present challenging requirements for manufactured surface figure and stability. By comparison, far infrared (IR) telescopes relax many of these requirements by ~100x. These relaxed requirements may translate into reduced cost, schedule, mass, and system complexity. This paper explores how different mirror substrate materials might take advantage of these requirements while operating in a cryogenic environment. Primary mirror materials are evaluated for an Origins Space Telescope (OST) concept, using a 9.1 m segmented aperture in a 30 μm diffraction limited system.
The HabEx mission concept is intended to directly image planetary systems around nearby stars, and to perform a wide range of general astrophysics and solar system observations. Its main goal is the discovery and characterization of Earthlike exoplanets through high-contrast imaging and spectroscopy. The baseline HabEx concept would use both a coronagraph and a starshade for exoplanet science. We describe an alternative, “HabEx Lite” concept, which would use a starshade (only) for exoplanet science. The benefit is lower cost: by deleting the complex coronagraph instrument; by lowering observatory mass; by relaxing tolerances and stability requirements; by permitting use of a compact on-axis telescope design; by use of a smaller launch vehicle. The scientific penalty of this lower cost option is a smaller number of detected exoplanets of all types, including exoEarth candidates, and a smaller fraction of exoplanets with measured orbits. Our approach uses a non-deployed segmented primary mirror, whose manufacture is within current capabilities.
Large, lightweight mirrors are a critical component in space based imaging applications. These mirrors have traditionally required long manufacturing cycle times with associated high costs. In this paper, the key cost and schedule drivers for the production of large, lightweight mirrors will be reviewed along with enabling solutions that could provide significant cost and schedule reductions while maintaining the high quality performance required for these challenging applications. The technologies include advancements in replication, construction, and bonding. Initial feasibility tests and associated results will be presented.
There is a continuous demand for larger, lighter, and higher quality telescopes. Over the past several decades, we have
seen the evolution from launchable 2 meter-class telescopes (such as Hubble), to today's demand for deployable 6
meter-class telescopes (such as JWST), to tomorrow's need for up to 150 meter-class telescopes. As the apertures
continue to grow, it will become much more difficult and expensive to launch assembled telescope structures. To
address this issue, we are seeing the emergence of new novel structural concepts, such as inflatable structures and
membrane optics. While these structural concepts do show promise, it is very difficult to achieve and maintain high
surface figure quality. Another potential solution to develop large space telescopes is to move the fabrication facility
into space and launch the raw materials.
In this paper we present initial in-space manufacturing concepts to enable the development of large telescopes. This
includes novel approaches for the fabrication of the optical elements. We will also discuss potential optical designs for
large space telescopes and describe their relation to the fabrication methods. These concepts are being developed to
meet the demanding requirements of DARPA's LASSO (Large Aperture Space Surveillance Optic) program which
currently requires a 150 meter optical aperture with a 16.6 degree field of view.
In this paper we describe a method to increase the spatial resolution of surface micro-roughness measurements. As the surface specifications for precision optics become more demanding, the metrology instruments must cover a broad spatial frequency range. Generally, multiple instruments are used to cover the full range of the specifications. For example, an interferometer (Fizeau, Michelson, etc.) would be used to test low spatial frequency surface errors, an interferometric microscope (such as a white light interferomenter) would be used for higher spatial frequency errors, and an AFM would be used for even higher spatial frequency errors. For some precision optics, three or more instruments would be necessary. However, an increase in the resolvable spatial frequency bandwidth of a metrology instrument could reduce the number of instruments necessary to characterize the optical surface over the spatial frequency bands defined by the optical specifications.
A solution to increase the resolvable spatial frequency bandwidth of micro-roughness measurements will be presented. This will be accomplished by implementing an interferometric microscope and a process called "sub-pixel spatial resolution interferometry" (SSRI) with interlaced stitching. In this process, multiple interferometric measurements are made as the optic under test (or the CCD array) is laterally shifted at sub-pixel increments. The measurements are then combined to construct a measurement with higher spatial resolution. Initial results obtained implementing a similar process used to increase the spatial resolution of measurements made with a commercially available Fizeau interferometer will be presented.
In this paper we describe a growing need for an increase in the spatial resolution of interferometric surface measurements of precision optics and present a new method to address this need. An increase in the spatial resolution of interferometric surface measurements arises from evolving surface figure and micro-roughness specifications for higher quality optics, demand for larger optics, and recent advancements in deterministic polishing. These three topics will be discussed and their relationship to increased spatial resolution will be described. A solution to increase the spatial resolution using a process called "sub-pixel spatial resolution interferometry" will be presented. In this process, multiple interferometric measurements are made as the optic under test (or the CCD array) is shifted at sub-pixel increments. The measurements are then combined to construct a measurement with higher spatial resolution than the original measurements. Initial results obtained using this process with a commercially available Fizeau interferometer will be presented.
Magneto-rheological finishing (MRF) is a deterministic figuring process capable of quickly achieving extreme surface accuracies. The commercially available Q22 has been instrumental in the manufacture of DUV lithography optics to better than 30 nm P-V figure and 1.0 nm rms microroughness. The requirements for EUV optics, photomask substrates, and silicon-on-insulator (SOI) wafers, however, have taken "extreme accuracy" to new levels. Surface quality is specified over a broad range of spatial frequencies, and allowable error magnitudes shrink ever smaller. These specifications expose some limitations of sub-aperture tool technologies. MRF capabilities, recent developments, and future system improvements that address these concerns are described. We present polishing results on photomasks that pass flatness requirements until year 2010. We further demonstrate extreme precision figure correction capability on SOI wafers, achieving thickness uniformity of better than 2 nm PV and 0.3 nm rms.
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