KEYWORDS: Telescopes, Mirrors, Space telescopes, Signal to noise ratio, Infrared telescopes, Optical fabrication, Observatories, Optical instrument design, Infrared radiation, James Webb Space Telescope
The WFIRST Mission is the next large astrophysical observatory for NASA after the James Webb Space Telescope and is the top priority mission from the 2010 National Academy of Sciences’ decadal survey. The WFIRST OTA includes the inherited primary and secondary mirrors with precision metering structures that are to be integrated to new mirror assemblies to provide optical feeds to the two WFIRST instruments. We present here: (1) the results for the review of the inherited hardware for WFIRST through a thorough technical pedigree process, (2) the status of the effort to establish the capability of the telescope to perform at a cooler operational temperature of 265K, and (3) the status of the work in requirement development for OTA to incorporate the inherited hardware, and (4) the path forward.
NASA’s Wide Field Infrared Survey Telescope (WFIRST) is being designed to deliver unprecedented capability in dark energy and exoplanet science, and to host a technology demonstration coronagraph for exoplanet imaging and spectroscopy. The observatory design has matured since 2013 [“WFIRST 2.4m Mission Study”, D. Content, SPIE Proc Vol 8860, 2013] and we present a comprehensive description of the WFIRST observatory configuration as refined during formulation phase (AKA the phase-A study). The WFIRST observatory is based on an existing, repurposed 2.4m space telescope coupled with a 288 megapixel near-infrared (0.6 to 2 microns) HgCdTe focal plane array with multiple imaging and spectrographic modes. Together they deliver a 0.28 square degree field of view, which is approximately 100 times larger than the Hubble Space Telescope, and a sensitivity that enables rapid science surveys. In addition, the technology demonstration coronagraph will prove the feasibility of new techniques for exoplanet discovery, imaging, and spectral analysis. A composite truss structure meters both instruments to the telescope assembly, and the instruments and the spacecraft are on-orbit serviceable. We present the current design and summarize key Phase-A trade studies and configuration changes that improved interfaces, improved testability, and reduced technical risk. We provide an overview of our Integrated Modeling results, performed at an unprecedented level for a phase-A study, to illustrate performance margins with respect to static wavefront error, jitter, and thermal drift. Finally, we summarize the results of technology development and peer reviews, demonstrating our progress towards a low-risk flight development and a launch in the middle of the next decade.
The Wide-Field Infrared Survey Telescope (WFIRST) mission is the next large astrophysics observatory for NASA after the James Webb Space Telescope and is the top priority mission from the 2010 National Academy of Sciences’ decadal survey. The WFIRST Optical Telescope Assembly (OTA) includes inherited composite support structures that were originally designed and tested for room temperature operation; however, the WFIRST mission will require operation at colder temperatures to achieve sufficient sensitivity for the infrared wavelengths. We will present the results and conclusions of testing completed at the coupon and engineering model level to verify that the inherited composite structures will maintain mechanical integrity and performance over the required temperature range. The testing included: (1) characterization testing of constituent material coupons, (2) thermal cycling and static load testing of a representative aft metering structure (AMS) and forward metering structure (FMS), and (3) thermal cycling and dynamic testing of a representative secondary mirror assembly (SMA).
KEYWORDS: Exoplanets, Space telescopes, Hubble Space Telescope, Telescopes, Observatories, Neodymium, James Webb Space Telescope, Aerospace engineering, Mirrors, Ultraviolet radiation
The Hubble Space Telescope has been a scientific marvel that has provided unimaginable imagery and scientific discovery. Its exquisite UV/Visible imaging performance is unmatched from the ground. In NASA’s future planning, the earliest possible successor mission would be in the 3030s, well beyond the expected lifetime of Hubble. The ASTRO-1 space telescope is a 1.8m off-axis (unobscured) observatory that looks to fill this critical void with Hubble-like performance to continue the scientific quest while also providing the possibility for exoplanet research with a coronagraphic instrument and/or a free flying starshade. BoldlyGo Institute seeks to reach beyond NASA funding to leverage the high public interest in space research and exploration, and the search for life beyond Earth.
KEYWORDS: Mirrors, Space mirrors, Glasses, Ultraviolet radiation, Plano, Lightweight mirrors, Polishing, Finite element methods, Computer aided design, Hubble Space Telescope
The Decadal Survey stated that an advanced large-aperture ultraviolet, optical, near-infrared (UVOIR) telescope is required to enable the next generation of compelling astrophysics and exoplanet science; and, that present technology is not mature enough to affordably build and launch any potential UVOIR mission concept. Under Science and Technology funding, NASA's Marshall Space Flight Center (MSFC) and Exelis have developed a more cost effective process to make up to 4m monolithic spaceflight UV quality, low areal density, thermally and dynamically stable primary mirrors. Under a Phase I program, a proof of concept mirror was completed at Exelis and tested down to 250K at MSFC which would allow imaging out to 2.5 microns. In 2014, Exelis and NASA started a Phase II program to design and build a 1.5m mirror to demonstrate lateral scalability to a 4m monolithic primary mirror. The current status of the Phase II development program will be provided along with a Phase II program summary.
The 2010 Decadal Survey stated that an advanced large-aperture ultraviolet, optical, near-infrared (UVOIR) telescope is required to enable the next generation of compelling astrophysics and exoplanet science; and, that present technology is not mature enough to affordably build and launch any potential UVOIR mission concept. Under Science and Technology funding, NASA’s Marshall Space Flight Center (MSFC) and Exelis have developed a more cost effective process to make 4m class or larger monolithic spaceflight UV quality, low areal density, thermally and dynamically stable primary mirrors. A proof of concept 0.43m mirror was completed at Exelis optically tested at 250K at MSFC which demonstrated the ability for imaging out to 2.5 microns. The parameters and test results of this concept mirror are shown. The next phase of the program includes a 1.5m subscale mirror that will be optically and dynamically tested. The scale-up process will be discussed and the technology development path to a 4m mirror system by 2018 will be outlined.
The Advance Mirror Technology Development (AMTD) project is in Phase 2 of a multiyear effort, initiated in FY12, to mature by at least a half TRL step six critical technologies required to enable 4 meter or larger UVOIR space telescope primary mirror assemblies for both general astrophysics and ultra-high contrast observations of exoplanets. AMTD continues to achieve all of its goals and accomplished all of its milestones to date. We have done this by assembling an outstanding team from academia, industry, and government with extensive expertise in astrophysics and exoplanet characterization, and in the design/manufacture of monolithic and segmented space telescopes; by deriving engineering specifications for advanced normal-incidence mirror systems needed to make the required science measurements; and by defining and prioritizing the most important technical problems to be solved.
Over the past two years, the New York Astronomical Corporation (NYAC), the business arm of the Astronomical Society of New York (ASNY), has continued planning and technical studies toward construction of a 12-meter class optical telescope for the use of all New York universities and research institutions. Four significant technical studies have been performed investigating design opportunities for the facility, the dome, the telescope optics, and the telescope mount. The studies were funded by NYAC and performed by companies who have provided these subsystems for large astronomical telescopes in the past. In each case, innovative and cost effective approaches were identified, developed, analyzed, and initial cost estimates developed. As a group, the studies show promise that this telescope could be built at historically low prices. As the project continues forward, NYAC intends to broaden the collaboration, pursue funding, to continue to develop the telescope and instrument designs, and to further define the scientific mission. The vision of a historically large telescope dedicated to all New York institutions continues to grow and find new adherents.
The most recent study of the Wide Field Infrared Survey Telescope (WFIRST) mission is based on reuse of an
existing 2.4m telescope. This study was commissioned by NASA to examine the potential science return and cost
effectiveness of WFIRST by using this significantly larger aperture telescope. We review the science program
envisioned by the WFIRST 2012-2013 Science Definition Team (SDT), an overview of the mission concept, and
the telescope design and status. Comparisons against the previous 1.3m and reduced cost 1.1m WFIRST design
concepts are discussed. A significant departure from past point designs is the option for serviceability and the
geostationary orbit location which enables servicing and replacement instrument insertion later during mission
life. Other papers at this conference provide more in depth discussion of the wide field instrument and the optional
exoplanet imaging coronagraph instrument.
KEYWORDS: Stars, Space telescopes, Telescopes, Coronagraphy, Space operations, Optical isolators, Control systems, Cameras, Point spread functions, Observatories
ACCESS (Actively-Corrected Coronagraph for Exoplanet System Studies) was one of four medium-class exoplanet
concepts selected for the NASA Astrophysics Strategic Mission Concept Study (ASMCS) program in 2008/2009 [14,
15]. The ACCESS study evaluated four major coronagraph concepts under a common space observatory. This paper
describes the high precision pointing control system (PCS) baselined for this observatory.
ACCESS is one of four medium-class mission concepts selected for study in 2008-9 by NASA's Astrophysics Strategic
Mission Concepts Study program. ACCESS evaluates a space observatory designed for extreme high-contrast imaging
and spectroscopy of exoplanetary systems. An actively-corrected coronagraph is used to suppress the glare of diffracted
and scattered starlight to contrast levels required for exoplanet imaging. The ACCESS study considered the relative
merits and readiness of four major coronagraph types, and modeled their performance with a NASA medium-class space
telescope. The ACCESS study asks: What is the most capable medium-class coronagraphic mission that is possible with
telescope, instrument, and spacecraft technologies available today? Using demonstrated high-TRL technologies, the
ACCESS science program surveys the nearest 120+ AFGK stars for exoplanet systems, and surveys the majority of
those for exozodiacal dust to the level of 1 zodi at 3 AU. Coronagraph technology developments in the coming year are
expected to further enhance the science reach of the ACCESS mission concept.
The Wide Field Coronagraph Telescope (WFCT) is a 4-meter space telescope for general astrophysics and exoplanet
observations that meets the 2000 Decadal Committee requirements.
This paper presents a design for a 4-m diameter, off-axis space telescope that offers high performance in both wide field
and coronagraphic imaging modes. A 3.8 x 3.3-m unobstructed elliptical pupil is provided for direct coronagraphic
imaging of exoplanets and a 4-m diameter pupil for wide-field imaging from far-ultraviolet (UV) to near-infrared (IR).
The off-axis wide-field optics are all reflective and designed to deliver an average of 12 nm wavefront aberrations over a
6 x 24 arcminute field of view (FOV), therefore providing diffraction-limited images down to 300 nm wavelength and
15 mas images down to a wavelength limit set only by the mirror coatings. The coronagraph with phase-induced
amplitude apodization (PIAA) provides diffraction suppression around a 360-degree field with high Strehl and
sensitivity at the 1e-10 level to an inner working angle of 2 λ/D (or 50 mas at 500 nm wavelength).
This paper focuses on the optical design that allows the above imaging features to be combined in single telescope, and
gives a preliminary spacecraft design and costing, assuming a distant trailing orbit.
KEYWORDS: Space telescopes, Telescopes, Earth observing sensors, High resolution satellite images, Space operations, Control systems, Mirrors, Telecommunications, Electronics, Astronomy
Modern astronomy currently is dealing with an exciting but challenging dichotomy. On one hand, there has been and
will continue to be countless advances in scientific discovery, but on the other the astronomical community is faced with
what unfortunately is considered by many to be an insurmountable budgetary impasse for the foreseeable future. The
National Academy of Sciences' Astro2010: Decadal Survey has been faced with the difficult challenge of prioritizing
sciences and missions for the upcoming decade while still allowing room for new, yet to be discovered opportunities to
receive funding. To this end, we propose the consideration of a paradigm shift to the astronomical community that may
enable more cost efficient space-based telescope missions to be funded and still provide a high science return per dollar
invested. The proposed paradigm shift has several aspects that make it worthy of consideration: 1) Telescopes would
leverage existing Commercial Remote Sensing Satellite (CRSS) Architectures such as the 1.1m NextView systems
developed by ITT, GeoEye-1, and WorldView-2, or the 0.7m IKONOS system (or perhaps other proprietary systems); 2)
By using large EELV class fairings, multiple telescopes with different science missions could be flown on a single
spacecraft bus sharing common features such as communications and telemetry (current Earth Science missions in early
development phases are considering this approach); 3) Multiple smaller observatories (with multiple spacecraft) could be
flown in a single launch vehicle for instances where the different science payloads had incompatible requirements; and
4) by leveraging CRSS architectures, vendors could supply telescopes at a fixed price. Here we discuss the implications
and risks that the proposed paradigm shift would carry.
KEYWORDS: Space telescopes, Control systems, Control systems design, Data modeling, Observatories, Telescopes, Active isolation, Space operations, Systems modeling, Exoplanets
Current concepts for some future for space based astronomical observatories require extraordinary stability with respect
to pointing and jitter disturbances. Exoplanet finding missions with internal coronagraphs require pointing stability of
<10nrad 3σ (<2mas, 3σ). Closed-loop active dynamic isolation at the interface between a telescope and the spacecraft
(where reaction wheels are the primary jitter source) can attain these requirements when incorporated with a robust
overall pointing control system architecture which utilizes information from IRUs, star-trackers, and steering mirrors.
ITT has developed a high TRL Active Isolation Mount System (AIMS) and through analyses and hardware test-bed
work demonstrated that these stringent pointing and dynamic stability can be met for the Actively-Corrected
Coronagraph for Exoplanet System Studies (ACCESS) [1] observatory.
ITT has patented and continues to develop processes to fabricate low-cost borosilicate mirrors that can be used for both
ground and space-based optical telescopes. Borosilicate glass is a commodity and is the material of choice for today's
flat-panel televisions and monitors. Supply and demand has kept its cost low compared to mirror substrate materials
typically found in telescopes. The current technology development is on the path to having the ability to deliver imaging
quality optics of up to 1m (scalable to 2m) in diameter in three weeks. For those applications that can accommodate the
material properties of borosilicate glasses, this technology has the potential to revolutionize ground and space-based
astronomy. ITT Corporation has demonstrated finishing a planar, 0.6m borosilicate, optic to <100 nm-rms. This paper
will provide an historical overview of the development in this area with an emphasis on recent technology developments
to fabricate a 0.6m parabolic mirror under NASA Earth Science Technology Office (ESTO) grant #NNX09AD61G.
The Pupil-mapping Exoplanet Coronagraphic Observer (PECO) mission concept uses a coronagraphic 1.4-m
space-based telescope to both image and characterize extra-solar planetary systems at optical wavelengths.
PECO delivers 10-10 contrast at 2 λ/D separation (0.15") using a high-performance Phase-Induced Amplitude
Apodization (PIAA) coronagraph which remaps the telescope pupil and uses nearly all of the light coming into
the aperture. For exoplanet characterization, PECO acquires narrow field images simultaneously in 16 spectral
bands over wavelengths from 0.4 to 0.9 μm, utilizing all available photons for maximum wavefront sensing and
sensitivity for imaging and spectroscopy. The optical design is optimized for simultaneous low-resolution spectral
characterization of both planets and dust disks using a moderate-sized telescope. PECO will image the habitable
zones of about 20 known F, G, K stars at a spectral resolution of R≈15 with sensitivity sufficient to detect
and characterize Earth-like planets and to map dust disks to within a fraction of our own zodiacal dust cloud
brightness. The PIAA coronagraph adopted for PECO reduces the required telescope diameter by a factor of two
compared with other coronagraph approaches that were considered for Terrestrial Planet Finder Coronagraph
Flight Baseline 1, and would therefore also be highly valuable for larger telescope diameters. We report on
ongoing laboratory activities to develop and mature key PECO technologies, as well as detailed analysis aimed
at verifying PECO's wavefront and pointing stability requirement can be met without requiring development of
new technologies.
ACCESS (Actively-Corrected Coronagraph for Exoplanet System Studies) develops the science and engineering case for
an investigation of exosolar giant planets, super-earths, exo-earths, and dust/debris fields that would be accessible to a
medium-scale NASA mission. The study begins with the observation that coronagraph architectures of all types (other
than the external occulter) call for an exceptionally stable telescope and spacecraft, as well as active wavefront
correction with one or more deformable mirrors (DMs). During the study, the Lyot, shaped pupil, PIAA, and a number
of other coronagraph architectures will all be evaluated on a level playing field that considers science capability
(including contrast at the inner working angle (IWA), throughput efficiency, and spectral bandwidth), engineering
readiness (including maturity of technology, instrument complexity, and sensitivity to wavefront errors), and mission
cost so that a preferred coronagraph architecture can be selected and developed for a medium-class mission.
The Universe appears to be expanding at an accelerating rate, driven by a mechanism called Dark Energy. The nature of Dark Energy is largely unknown and needs to be derived from observation of its effects. JEDI (Joint Efficient Dark-energy Investigation) is a candidate implementation of the NASA-DOE Joint Dark Energy Mission (JDEM). It will probe the effects of Dark Energy in three independent ways: (1) using Type Ia supernovae as cosmological standard candles over a range of distances, (2) using baryon acoustic oscillations as a cosmological standard ruler over a range of cosmic epochs, and (3) mapping the weak gravitational lensing distortion by foreground galaxies of the images of background galaxies at different distances. JEDI provides crucial systematic error checks by simultaneously applying these three independent observational methods to derive the Dark Energy parameters. The concordance of the results from these methods will not only provide an unprecedented understanding of Dark Energy, but also indicate the reliability of such an understanding. JEDI will unravel the nature of Dark Energy by obtaining observations only possible from a vantage point in space, coupled with a unique instrument design and observational strategy. Using a 2 meter-class space telescope with simultaneous wide-field imaging (~ 1 deg2, 0.8 to 4.2 μm in five bands) and multi-slit spectroscopy (minimum wavelength coverage 1 to 2 μm), JEDI will efficiently execute the surveys needed to solve the mystery of Dark Energy.
The Terrestrial Planet Finder Coronagraph (TPF-C) is conducting pre-formulation design and analysis studies based on a 8x3.5m elliptical aperture, light-weight primary mirror feeding an internally occulted (Lyot) coronagraph. The primary mirror has challenging static and dynamic performance requirements. We report on recent trade studies and concepts including open- and closed-back mirror blank designs and comparisons of thermal and mechanical performance; aperture shape alternatives to better match the coronagraph application with weight, packaging, and fabrication constraints; and mirror material trades.
KEYWORDS: Mirrors, Actuators, Computer aided design, Error analysis, Space based lasers, Control systems, Composites, Space mirrors, Optical fabrication, Solid modeling
The Advanced Mirror System Demonstrator program sponsored by NASA, the Space Based Laser Joint Venture Team, and the National Reconnaissance Office provides an opportunity to design and build a demonstration model of the next generation primary mirrors that will be needed for future space programs. This paper discusses the history of this technology at Kodak and provides an overview of the analysis techniques used in the design and performance prediction process.
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