Building the Eyes of a Lynx
The Lynx X-ray Mirror Assembly is the most powerful X-ray optic ever conceived. We know how to build it. A new, independent Industry Report by Northrop Grumman and L3Harris shows how it can be done.
The Lynx X-ray Mirror assembly is the most powerful X-ray optic ever conceived. We know how to build it.
This Industry report by Northrop Grumman and L3Harris takes a deep-dive into a feasible, optimized, and parallelized manufacturing plan. This is a ground-up study by two companies with world-leading, decades-long experience in these specialized areas. It is led by two world-class experts: Jon Arenberg (Chief Engineer for Space Science Missions at Northrop Grumman) and Lynn Allen (Senior Manager for Precision Optics at L3Harris).
The report’s ultimate conclusion? No, the Lynx mirror is not too large to manage, nor it is an unprecedented manufacturing job.
The study also developed an Industry-led ground-up grassroots mirror cost estimate, whose bottom line number is fully consistent with the Lynx team’s internal estimate.
More posts about the Lynx X-ray Mirror Assembly:
The Lynx Legacy Field
The Shape of the Expanse
Press play above to view a zoom-out animation of the Lynx Legacy Field
the Shape of the Expanse
The Lynx Legacy Field, a 10 square degree map of the largest structures in the Universe, is a notional 10 megasecond program that would reign among the Observatory’s most revolutionary achievements. Focused on a previously identified low-redshift large scale structure, this survey will reveal a massive galaxy cluster anchored to the void by Cosmic Web filaments that have, thus far, never been truly observed.
The full image above shows a realistic mock of soft X-ray surface brightness from the Hydrangea simulation, with a true Lynx surface brightness sensitivity cutoff applied. A large mosaic of individual 100 ksec HDXI exposures, the Legacy Field will maintain sub-arcsecond imaging across the entire field, and every individual 100 ksec footprint in the mosaic will reach a greater depth than the deepest region of the 7 Msec Chandra Deep Field South. While the image of the filamentary web and its cluster-scale node will be a revolutionary achievement on its own, even individual “blank” regions of the image would contain an exquisite array of high- and low-redshift AGN, clusters, and groups. This is illustrated in the bottom two panels of the above figure, which show (at bottom left) a zoom-in on a simulated single 100 ksec HDXI footprint of a “blank” region of the Legacy Field. Nearly seven thousand discrete sources will be detected in a single 22′×22′ field of view. It is the ability to detect and mask these sources that gives Lynx access to the very low surface brightness levels needed to reveal the Cosmic Web. The lower right panel shows a further zoom-in on this “blank” field exposure, revealing a blindly detected 10¹³ solar mass galaxy group at redshift z = 3.27, the epoch of formation of the earliest galaxy groups and protoclusters. The Lynx Legacy Field will be among the richest X-ray datasets ever obtained, and reign as a lasting triumph of science.
Dr. William Zhang wins NASA Goddard Technology Award
NASA Scientist Dr. William Zhang wins the 2019 Goddard IRAD Innovator of the Year Award. Zhang’s team is behind the revolutionary X-ray optics that power the Lynx X-ray Observatory, a revolutionary NASA Large Mission Concept Study now under consideration by the 2020 Decadal Survey.
By Lori Keesey
NASA’s Goddard Space Flight Center
NASA scientist William Zhang wasn’t always a mirror-making whiz. In fact, this year’s IRAD (Internal Research and Development) Innovator of the Year at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, started his career working underground — literally.
Zhang won the Goddard Office of the Chief Technologist’s top prize — bestowed annually on those who demonstrate the best in innovation — for his foresight, perseverance, and leadership advancing state-of-the-art X-ray optics.
In particular, he and his team created a new type of mirror made of mono-crystalline silicon, an abundantly available material commonly used to manufacture computer chips. The new mirror type is now baselined for use on the conceptual Lynx X-ray Observatory — one of four potential missions that scientists have vetted as worthy of consideration by the 2020 Decadal Survey for Astrophysics.
The 2019 Goddard IRAD Innovator of the Year William Zhang holds one of the X-ray mirror segments that he and his team manufactured from mono-crystalline silicon — a material never before configured for capturing high-energy X-ray photons.
Credits: NASA/Chris Gunn
Illustration of the conceptual Lynx X-ray Observatory, a potential user of a new X-ray mirror developed by Goddard astrophysicist William Zhang.
Credits: NASA and The Lynx Team
After a stint with Los Alamos National Laboratory in New Mexico, Zhang came to the center specifically to build and calibrate the Proportional Counter Array that flew on the Rossi X-ray Timing Explorer that launched in late 1995. With scientific papers published in technical journals, Zhang began casting about for a new challenge and got one when his former boss suggested he apply his talents to Constellation-X, a conceptual X-ray mission at the time.
“Optics turned out to be the most important technology for X-ray astronomy,” Zhang said, adding that these highly specialized mirror segments are curved and aligned inside a canister-type assembly to collect highly energetic X-ray photons emanating from hot objects, such as pulsars, galactic supernovae remnants, and the accretion disk of black holes.
Because the mirrors are curved, X-ray photons graze their surfaces — much like skipping stones — and deflect into an observatory’s instruments rather than passing through them. “They had a default technique for making these optics and I thought it wasn’t working very well.”
The key, he reasoned, was making these optics much thinner, lighter, and less expensive to manufacture. If the individual mirror segments were thick and heavy, like those employed by NASA’s Chandra X-ray Observatory, fewer mirrors could fly, limiting the observatory’s collecting area and therefore its sensitivity or ability to discern details of an astronomical target.
Before Zhang set out to tackle the challenge, optics developers traditionally used glass, ceramics, and metals. However, these materials suffer from high internal stress, especially when cut or exposed to changing temperatures. These stresses become increasingly more unpredictable as the mirror becomes thinner.
Zhang and his team prevailed.
As part of a study evaluating the conceptual Lynx telescope, a NASA-commissioned panel of 40 experts found that the optics could provide sub-arcsecond resolution, which is the same quality as the four pairs of larger, much heavier mirrors flying on Chandra. Furthermore, because the mirrors are 50 times lighter and less costly to build than Chandra’s, next-generation observatories can carry literally tens of thousands of mirror segments, improving sensitivity over even Chandra, the world’s most powerful X-ray observatory.
In addition to being baselined on Lynx, the mirror technology is now being investigated for potential use on the European Space Agency’s Athena X-ray Observatory, scheduled to launch in late 2031. Even if Lynx isn’t selected as NASA’s next flagship astrophysics mission, other NASA missions could benefit in the future, he said.
In the nearer term, Zhang will be flying his optics on a sounding rocket mission, called OGRE, in 2021. This flight opportunity will represent the technology’s first demonstration in space. For OGRE, which is short for the Off-plane Grating Rocket Experiment, Zhang is developing a 288-segment mirror assembly.
“I had many moments when I thought I had bitten off more than I could chew,” Zhang said, reflecting on his technology-development effort, which is continuing as he works with his engineering team to design an improved technique for aligning and bonding these fragile mirror segments inside a protective canister. “With technology development, you never know if you’ll achieve what you set out to achieve. But I’m fortunate that I work with a team of people who are really, really good. Teamwork isn’t an empty word. It’s precious and very, very important.”
“Will saw a need and pursued the mirror-making concepts with tenacity,” said Goddard Chief Technologist Peter Hughes. “Silicon has never been used to make super-thin, lightweight, easily reproducible X-ray mirrors. His innovation could represent a paradigm shift in X-ray astronomy for decades to come. Certainly, Will and his team have reinvented the way NASA builds these highly specialized mirrors. He is the poster child for how to advance innovative new technologies.”
Though he has proven his mettle in mirror making, Zhang actually started his career as a particle physicist and detector scientist. As a graduate student at the University of Pennsylvania, he spent his daylight hours searching for neutrinos at the Kamioka Observatory located in the Mozumi mine two miles beneath a mountain peak in western Japan — a site chosen so that cosmic rays wouldn’t interfere with the measurements.
Although the experiment did not succeed in detecting proton decay, which was its original purpose, it successfully detected neutrinos from supernova 1987A and the Sun using state-of-the-art electronics and data-acquisition systems that Zhang helped build.
The experience served another useful purpose.
“I’d go down there before sunrise and wouldn’t come back up until nightfall,” Zhang recalled. After three years as a subterranean worker, “I discovered I would prefer having an office with windows. I had enough of mining.”
It’s a good thing for Goddard.
IRAD Innovator of the Year William Zhang and his team succeeded in developing a new type of X-ray mirror. Team members include (from left to right): Michael Norman, Michal Hlinka, John Kearney, Kim Allgood-Puckett, Michael Biskach, James Mazzarella, William Zhang, Ryan McClelland, Raul Riveros, Ai Numata, and Peter Solly. Not pictured: Kai-Wing Chan and Timo Saha.
Credits: NASA/Chris Gunn
This particle beam polishes the surfaces of a new X-ray mirror made of silicon.
Credits: NASA/Chris Gunn
With support from Goddard’s IRAD program and other NASA research and development programs, he first experimented with glass slumping, a novel technique where he placed commercially available, super-thin glass segments on a mandrel, or mold, and heated the entire assembly in an oven. As the glass heated, it softened and folded over the mold to produce a cylindrically shaped optic that was then coated with layers of silicon and tungsten to maximize their X-ray reflectance.
Though Zhang proved the technique and produced 10,000 modest-resolution mirrors ideal for NASA’s Nuclear Spectroscopic Telescope Array, or NuSTAR, mission, Zhang realized he had taken this technique to the limit. He concluded that their performance was inadequate for achieving the desired sensitivity for future X-ray telescopes.
He turned to single-crystal silicon, a material never polished and figured for lightweight X-ray optics. The material itself intrigued him. Inexpensive and abundantly available because the semiconductor industry uses it to manufacture computer chips, crystalline silicon has little, if any, internal stresses, making it ideal for creating super-thin X-ray optics.
Leveraging his experience with glass slumping, Zhang started with blocks of silicon. With standard machining tools, he produced the approximate mirror shape and then used precision machining tools and chemicals to further grind and refine the blocks’ surfaces. Like slicing cheese, he then cut thin substrates measuring less than a millimeter in thickness and polished their surfaces. Any surface defects larger than several nanometers were removed with a special ion-beam polishing tool.
Read an independent report by Northrop Grumman and L3Harris on the feasibility of manufacturing the Lynx X-ray Mirror Assembly.
The Lynx Technology Roadmaps
As supplements to our Concept Study Report, the Lynx Team has also published more than 200 additional pages of detailed Technology Development Roadmaps for the Mirror Assembly and all three of our Science Instruments. You can read them using the links below:
LYNX MIRROR ASSEMBLY
LYNX SCIENCE INSTRUMENTS
Podcast: The Future of Discovery with Lynx
Following the public release of our Concept Study Report, our very own Dr. Jessica Gaskin, the NASA Study Scientist for Lynx, joined WLRH for their Public Radio Hour to discuss our vision for a new epoch of discovery. Dr. Gaskin appeared alongside the inimitable Dr. Martin Weisskopf, Chandra X-ray Observatory Project Scientist at the Marshall Space Flight Center, who discussed Chandra’s two decades of discovery.
Dr. Gaskin’s segment on Lynx starts at the 31 minute mark.
Dr. Jessica Gaskin, NASA Study Scientist for the Lynx Concept Study
Dr. Martin Weisskopf, Chandra X-ray Observatory Project Scientist
One Journey Ends. Another Begins.
A nearly four year Concept Study. A decade of dreams. Hundreds of people from across the globe. One vision for a New Great Observatory.
The Lynx Team is proud to present our roadmap toward a new epoch of discovery. Read our Concept Study Report here, and find our Technology Supplements, including our Mirror and Instrument Technology Roadmaps, at our official NASA site.
Why a Lynx?
An early Lynx mission branding concept from Illustrator David Miller.
Lynx isn't an acronym. It is a name with a deep connection to the history of Astronomy.
Galileo Galilei (1564-1642) was a proud member of Italy's Accademia dei Lincei (Academy of the Lynx), a scientific society devoted to investigations of the natural world. Federico Cesi, who founded the "Lincean Academy" in 1603, named it after the lynx, whose sharp vision evokes the observational prowess on which scientific progress relies. It was in one early meeting of the academy that the term "telescope" was first coined. The Lincean Academy exists to this day as the Accademia Nazionale dei Lincei, effectively serving as Italy's National Academy of Science.
Galileo Galilei was a member of Italy's Accademia dei Lincei (Academy of the Lynx).
The lynx is a feline with keen eyesight and, in many cultures and traditions, is a symbol of great insight and the supernatural ability to see through to the true nature of things.
Illustration from Urania's Mirror, a set of star charts engraved by Sydney Hall and published in 1824. Lynx was a constellation proposed in 1687 by Polish astronomer Johannes Hevelius, and consisted of 19 stars spanning the gulf between Ursa Major and Auriga. Hevelius named the constellation after a Lynx because it was so faint, and stated that only the "lynx-eyed" would be able to find it.
Our mission concept was originally dubbed the "X-ray Surveyor", but our team felt that Lynx was a perfect name to evoke the major scientific themes of our mission, all of which relate to the "unseen" or the "invisbile".
That the name ended with an "X" didn't hurt, either.
Our mission's logo is evocative of rays of light, grazing incidence mirror shell segments, and, of course, X-rays. You can learn more about Lynx mission branding here.
Big things have small beginnings
Welcome
Lynx is an observatory for all. Not just all astronomers - all people. NASA's Great Observatories like Hubble and Chandra embody this grand tradition. Yes, they deliver great science, but they also inspire the public to pursue a greater understanding of the world (and Universe!) around them. Even mission concepts, then, should welcome and inspire interest from and within the global public.
It is in this spirit that we are excited and proud to launch the new platform upon which we will share the vision, story, and journey of Lynx with the world.
What you see here is merely a beginning. Content will be ever changing, our mission blog will expand with frequent posts from members of the Lynx Team, and we will keep the community up-to-date with news before, during, and after the meeting of the 2020 Decadal Survey.
Today marks the start of the XXXth IAU General Assembly in Vienna, and we are celebrating with the launch of our new website. The Lynx Twitter and Facebook accounts will be actively involved in #IAU2018, and we have far bigger plans to come for the 233rd AAS Meeting in Seattle (January 6-10, 2019).
We may be launching in the 2030s, but our journey begins today. Join us.