. | . |
NASA Team Takes on a New Optical Challenge - the Lyman Alpha Limit by Lori Keesey for GSFC News Greenbelt MD (SPX) May 31, 2017
NASA technologists produced telescope mirrors with the highest reflectance ever reported in the far-ultraviolet spectral range. Now, they're attempting to set another record. Manuel Quijada and his team, optical experts at NASA's Goddard Space Flight Center in Greenbelt, Maryland, are investigating techniques for creating highly reflective aluminum mirrors sensitive to the infrared, optical, and far-ultraviolet wavelength bands - a broad spectral range envisioned for proposed space telescopes after the James Webb Space Telescope and Wide Field Infrared Survey Telescope. These proposed missions would tackle a broad range of astrophysics studies, from the epoch of reionization, through galaxy formation and evolution, to star and planet formation. Quijada's team specifically is studying three different techniques and materials for creating and applying protective coatings on aluminum mirrors to prevent them from oxidizing when exposed to oxygen and losing their reflectivity. "Aluminum is a metal that nature has given us the broadest spectral coverage," Quijada said. "However, aluminum needs to be protected from naturally occurring oxides with a thin film or substrate of transparent material." Unfortunately, no one has developed a coating that effectively protects and maintains a mirror's high reflectivity in the 90- to 130-nanometer range, also known as the Lyman Alpha range. At this spectral regime, scientists can observe a rich assortment of spectral lines and astronomical targets, including potentially habitable planets beyond our solar system. "The low reflectivity of coatings in this range is one of the biggest constraints in far-ultraviolet telescope and spectrograph design," Quijada said. Ultraviolet light, which is shorter than that of visible light but longer than X-rays, is invisible to the human eye. Only with instruments tuned to this wavelength can objects be observed. One of the recent NASA missions fully dedicated to far-ultraviolet observations was the Far Ultraviolet Spectroscopic Explorer, or FUSE, which was decommissioned in 2007 after a successful prime mission. Although it acquired 6,000 observations of nearly 3,000 separate astronomical objects over its eight years in orbit, FUSE's lithium fluoride substrate coating was not stable enough and began to degrade with time, Quijada said. Quijada's goal is to develop a coating and process that not only improves reflectance in the far ultraviolet, but also allows observations in the other wavelength bands. "Traditional coating processes have not allowed the use of aluminum mirrors to their full potential," Quijada said. "The new coatings we're investigating would enable a telescope covering a very broad spectral range, from the far ultraviolet to the near-infrared in one single observatory. NASA would get more bang for the buck." Under one coating approach, the team would use physical vapor deposition to apply a thin layer of xenon difluoride gas to an aluminum sample. According to Quijada, studies have shown that the treatment of xenon difluoride creates fluorine ions that tightly bind to the aluminum surface, preventing further oxidation. He also is investigating the use of two other thin-film deposition techniques - ion-assisted physical vapor deposition and atomic layer deposition - to apply thin films of aluminum trifluoride, which is environmentally stable compared with other coatings. Quijada and his team already have succeeded in developing a coating for another region of the ultraviolet spectral band. In 2016, a validation test proved that a protective coating that the team devised provided 90 percent reflectance in the 133.6-154.5 nanometer range - the highest reflectance ever reported for this ultraviolet band. To achieve this unprecedented level of performance, the team developed a three-step physical vapor deposition process to coat aluminum mirrors with protective magnesium fluoride or lithium fluoride films. These high-reflectance coatings are now enabling new types of instruments, Quijada said. Two new heliophysics missions that will study the interactions between Earth's ionosphere and solar winds - the Ionospheric Connection Explorer and the Global-scale Observations of the Limb and Disk -will employ this coating technology. "We need to push further down in the ultraviolet spectrum," Quijada said, referring to the targeted far-ultraviolet spectral range. "We need to get access to the whole ultraviolet to infrared range. We are blazing a trail in mirror coatings." For more NASA technology news go here
Beijing (XNA) May 30, 2017 China's new space telescope to be launched soon will probe many mysteries of the universe, including the belching "big eaters" - active galactic nuclei at the most remote edges of the universe. Scientists have discovered that almost every galaxy has a supermassive black hole with a mass several million to several billion times that of the Sun at its center. With their mighty gravitational ... read more Related Links Technology at NASA Stellar Chemistry, The Universe And All Within It
|
|
The content herein, unless otherwise known to be public domain, are Copyright 1995-2024 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us. |