Enhanced far-ultraviolet reflectance of MgF<sub>2</sub>and LiF over-coated Al mirrors

Quijada, Manuel A.; Hoyo, Javier del; Rice, S. H.

doi:10.1117/12.2057438

Cited by 31 publications

(37 citation statements)

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“…This results in a peak FUV reflectivity ∼ 30% less than the theoretical reflectivity predicted by the optical constants of bulk LiF crystal and aluminum [11,18]. Recent progress in new PVD techniques developed at the NASA Goddard Space Flight Center (GSFC) Thin Films Coating Laboratory (TFCL) have produced LiF+Al thin films with higher reflectivity in the LUV and lower surface roughness than has previously been obtained for astronomical optics [19]. These new enhanced LiF+Al coatings (eLiF) promise to reduce absorption and scatter losses, improving the bandpass and throughput for next-generation ultraviolet space observatories ( Fig.…”

Section: Introductionmentioning

confidence: 94%

“…The hygroscopic degradation of LiF can be mitigated by maintaining a dry integration and testing environment, typically with N 2 purging of the instrument when not in vacuum, such as on the NASA Explorer mission FUSE [14] and on numerous sounding rocket experiments [21,22]. For large missions such as LUVOIR, the risk associated with maintaining those measures on dozens of meter-class optics may be prohibitive, and therefore a means of permanently protecting the LiF from moisture The theoretical reflectivity of (orange) bare aluminum and (red) LiF+Al, along with the measured reflectivity of (blue) FUSE witness samples and (black) eLiF samples for which the LiF layer thicknesses were estimated as shown [19,20]. exposure is desirable.…”

Section: Introductionmentioning

confidence: 99%

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Advanced environmentally resistant lithium fluoride mirror coatings for the next generation of broadband space observatories

et al. 2017

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Recent advances in the physical vapor deposition (PVD) of protective fluoride films have raised the far ultraviolet (FUV: 912 -1600 Å) reflectivity of aluminum-based mirrors closer to the theoretical limit. The greatest gains, at more than 20%, have come for lithium fluoride protected aluminum (LiF+Al), which has the shortest wavelength cutoff of any conventional overcoat. Despite the success of the NASA FUSE mission, the use of LiF-based optics is rare as LiF is hygroscopic and requires handling procedures that can drive risk. With NASA now studying two large mission concepts for astronomy (LUVOIR and HabEx) that mandate throughput down to 1000 Å, the development of LiF-based coatings becomes crucial. This paper discusses steps that are being taken to qualify these new enhanced LiF protected aluminum (eLiF) mirror coatings for flight. In addition to quantifying the hygroscopic degradation, we have developed a new method of protecting eLiF with an ultrathin (10 -20 Å) capping layer of a non-hygroscopic material to increase durability. We report on the performance of eLiF-based optics and assess the steps that need to be taken to qualify such coatings for LUVOIR, HabEx, and other FUV-sensitive space missions.

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Section: Introductionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Advanced environmentally resistant lithium fluoride mirror coatings for the next generation of broadband space observatories

et al. 2017

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“…NASA's 2014 COR Technology Report lists "High-Reflectivity Optical Coatings for UV/Vis/NIR" as the most important goal for Cosmic Origins (Item #1 on Priority 1 list). SISTINE will provide the first test of advanced Al+LiF coatings 25 on shaped optics and the first flight test of these coatings. Items #2 and #3 on the COR Priority 1 list both deal with large format and photon-counting UV detectors.…”

Section: Chess the Colorado High-resolution Echelle Stellar Spectrogmentioning

confidence: 99%

“…The system is designed for R ≈ 10,000 spectroscopy across the 1000 -1600 Å bandpass with imaging performance between 0.5 -2.0′′ depending on the field position and wavelength (optimized for R ≈ 11,900 and Δθ ≈ 0.5′′ at Lyα; Figure 11). SISTINE employs the new advanced Al+LiF ("eLiF", see above) coatings developed at GSFC 25 and is projected to deliver a peak effective area of Aeff ≈ 170 cm 2 at Lyα, enabling high-sensitivity, moderate-resolution, astronomical imaging spectroscopy across this bandpass for the first time. SISTINE's f/16 telescope consists of a 0.5 m diameter parabolic primary mirror and a 86 mm convex hyperbolic secondary ( Figure 11).…”

Section: Sistine -Suborbital Imaging Spectrograph For Transition Regimentioning

confidence: 99%

“…In Table 1, we briefly outline how CHISL supports each of NASA's Key Science Goals for LUVOIR noted in Section1. CHISL anticipates a moderately slow (> f/12) incident beam from an optical telescope assembly that has optical coatings compatible with high throughput broadband performance and wavefront control The origins of stars and planets X [25][26][27] . CHISL will have a slit assembly for the moderate resolution imaging mode, as well as a secondary aperture for an echelle mode that will feed a collimating fore-optic.…”

Section: The Combined High-resolution and Imaging Spectrograph For Thmentioning

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CHISL: the combined high-resolution and imaging spectrograph for the LUVOIR surveyor

Fleming

Hoadley

2016

J. Astron. Telesc. Instrum. Syst

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NASA is currently carrying out science and technical studies to identify its next astronomy flagship mission, slated to begin development in the 2020s. It has become clear that a Large Ultraviolet/Optical/IR (LUVOIR) Surveyor mission (dprimary ≈ 12 m, Δλ ≈ 1000 Å -2 µm spectroscopic bandpass) can carry out the largest number of NASA's exoplanet and astrophysics science goals over the coming decades. The science grasp of a LUVOIR Surveyor is broad, ranging from the direct detection of potential biomarkers on rocky planets to the flow of matter into and out of galaxies and the history of star-formation across cosmic time. There are technical challenges for several aspects of the LUVOIR Surveyor concept, including component level technology readiness maturation and science instrument concepts for a broadly capable ultraviolet spectrograph. We present the scientific motivation for, and a preliminary design of, a multiplexed ultraviolet spectrograph to support both the exoplanet and astrophysics goals of the LUVOIR Surveyor mission concept, the Combined High-resolution and Imaging Spectrograph for the LUVOIR Surveyor (CHISL). CHISL includes a highresolution (R ≈ 120,000; 1000 -1700Å) point-source spectroscopy channel and a medium resolution (R ≥ 14,000 from 1000 -2000 Å in a single observation and R ~ 24,000 -35,000 in multiple grating settings) imaging spectroscopy channel. CHISL addresses topics ranging from characterizing the composition and structure of planet-forming disks to the feedback of matter between galaxies and the intergalactic medium. We present the CHISL concept, a small sample of representative science cases, and the primary technological hurdles. Technical challenges include high-efficiency ultraviolet coatings and high-quantum efficiency, large-format, photon counting detectors. We are actively engaged in laboratory and flight characterization efforts for all of these enabling technologies as components on sounding rocket payloads under development at the University of Colorado. We describe two payloads that are designed to be pathfinder instruments for the high-resolution (CHESS) and imaging spectroscopy (SISTINE) arms of CHISL. We are carrying out this instrument design, characterization, and flight-testing today to support the new start of a LUVOIR Surveyor mission in the next decade.Keywords: flagship mission: LUVOIR, ultraviolet spectroscopy, suborbital payloads, science drivers, photon-counting detectors, optical coatings LUVOIR SURVEYORThe 2010 Astronomy and Astrophysics Decadal Survey (New Worlds, New Horizons) recommended an augmentation of the NASA technology development budget for hardware supporting both a mission capable of direct spectroscopy of Earth-like planets and a large UV astrophysics mission to serve as a successor to HST 1 . These recommendations built on several exercises for Probe-class (cost ~$1B) missions during the 2000s and numerous white papers making the science case for an Advanced Technology Large Aperture Space Telescope (ATLAST) mission submitted to the 20...

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The Polstar high resolution spectropolarimetry MIDEX mission

Scowen

Gayley

Ignace

et al. 2022

Astrophys Space Sci

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Enhanced far-ultraviolet reflectance of MgF₂and LiF over-coated Al mirrors

Cited by 31 publications

References 6 publications

Advanced environmentally resistant lithium fluoride mirror coatings for the next generation of broadband space observatories

Advanced environmentally resistant lithium fluoride mirror coatings for the next generation of broadband space observatories

CHISL: the combined high-resolution and imaging spectrograph for the LUVOIR surveyor

The Polstar high resolution spectropolarimetry MIDEX mission

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Enhanced far-ultraviolet reflectance of MgF2and LiF over-coated Al mirrors

Cited by 31 publications

References 6 publications

Advanced environmentally resistant lithium fluoride mirror coatings for the next generation of broadband space observatories

Advanced environmentally resistant lithium fluoride mirror coatings for the next generation of broadband space observatories

CHISL: the combined high-resolution and imaging spectrograph for the LUVOIR surveyor

The Polstar high resolution spectropolarimetry MIDEX mission

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Product

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Enhanced far-ultraviolet reflectance of MgF₂and LiF over-coated Al mirrors