This image of spiral galaxy NGC 1300 combines observations to map stellar populations and gas. Photo courtesy of NASA

NASA’s James Webb Space Telescope, the most ambitious and complex space observatory ever built, will use its unparalleled infrared capabilities to study Jupiter’s Great Red Spot. Photo courtesy of NASA

Calling the James Webb Space Telescope an "eye in the sky" barely hints at its power, precision and vast capabilities. Launched by NASA in December, 2021 following years of research and development, and an investment of $10 billion, the Webb Telescope is by far the most sensitive and sophisticated instrument of its type ever developed, a pinnacle of scientific achievement. Its ambitious mission, to peer into space and provide clear images of distant planets, stars and whole galaxies that are light years away from Earth, is unprecedented in scope and complexity.

Yet on a fundamental level, the eye in the sky metaphor is fitting. NASA scientists refer to its main feature—an expandable, 6.5 meter (21 feet 4 inch) primary mirror consisting of Webb’s 18 hexagonal segments—as the “pupil.” Designed to capture light from some of the faintest objects in the universe, the calculations and calibrations required to keep its “vision” sharp are called a “prescription.”

And that’s not all. The Shack-Hartmann WaveFront Sensor, which is used to measure wavefront aberrations in materials such as silicone wafer, contact lenses, IOL's and the eye, is used to measure the polished surface of the telescope’s mirrors.

The James Webb Space Telescope mirrors completing deep-freeze tests in the x-ray and cryogenic test facility at Marshall Space Flight Center in Huntsville, Alabama. Photo courtesy of NASA

The principal scientist in charge of the design and maintenance of this high-tech oculus is Lee Feinberg, a 30-year NASA veteran who previously worked on the Hubble telescope. As NASA’s optical telescope element manager, Feinberg not only played a key role in designing the Webb’s mirror, he also serves as its “eye doctor,” diagnosing and fixing any visual problems that may develop during its long-distance, multi-year voyage.

Lee Feinberg, NASA’s optical telescope element manager. Photo courtesy of NASA

I spoke with Feinberg in mid-January, just six weeks after the Webb telescope was launched on Christmas Day. He described his work on the mission and talked about how his own vision journey led him down his unique career path. The following dialogue is excerpted from our interview. It has been edited for length and clarity.

Andrew Karp: It's been 13 days since the Webb went into orbit around the sun, a million miles from Earth. How’s the mission going? What are some of the most significant learnings from the past two weeks?

Lee Feinberg: Well, so far, we're really happy with everything. You know, the first couple of weeks we had the large deployments. There’s a large, sunshield about the size of a tennis court that had to unfold with five membrane layers. And then the telescope itself had to literally unfold, the secondary mirror had to deploy out almost eight meters and the wings with three nerves each all had to deploy. And all that went very well. And just this week we got the very first photons through the telescope and into the science instrument, and we are looking at getting our very first data. We're starting the alignment of the telescope.

AK: Any surprises so far?

The James Webb Space Telescope launching from Arianespace's ELA-3 launch complex at Europe's Spaceport located near Kourou, French Guiana. Photo courtesy of NASA

This large, sunshield which protects the Webb telescope from extreme temperatures is about the size of a tennis court and consists of five membrane layers. Photo courtesy of NASA

LF: This is a cold telescope, it's designed to be about minus 400 degrees Fahrenheit, the telescope part, that's why we put up this large sunshield to kind of block the sun out at the altitude of the Lagrange Point. (Lagrange Points are positions in space where the gravitational forces of a two body system like the Sun and the Earth produce enhanced regions of attraction and repulsion. These can be used by spacecraft to reduce fuel consumption needed to remain in position.) And a lot of what we've been paying very close attention to is the cooling rates and how things are cooling down. Some things cooled a little faster, some things a little slower. In general, though, we've been really pleased with the performance of everything. We're getting to know our observatory and our spacecraft.

AK: You’ve been working on space telescopes for much of your career, including the Hubble telescope. Can you briefly summarize what your work involves?

LF: It's really evolved. Because when I started on the Hubble, it was actually the first mission to fix Hubble. Then I was the youngest person on the team. I was going out to the vendor that made the little mirrors, the corrective optics that fix Hubble and I was literally testing those mirrors and doing sort of independent analyses and helping with the instruments in the cleanroom. So I started out as an engineer really doing testing and figuring out, you know, do we have the right prescription and do the mirrors seem like they're the right mirrors.

Then I became what's called an instrument manager. And on the second service mission, I was actually in charge of, at least for NASA, the Space Telescope Imaging Spectrograph, which was a very complicated spectrograph that we launched on the second mission to upgrade Hubble, and help design some of the next generation missions as well as help with the selection of them. But then I actually went on to do some technology for a few years.

Quick Facts About the James Webb Space Telescope

The Webb observatory is NASA’s revolutionary flagship mission to seek the light from the first galaxies in the early universe, and to explore our own solar system, as well as nearby planets orbiting other stars, called exoplanets.

This image of spiral galaxy NGC 3351 combines observations from several observatories to reveal details about its stars and gas. Photo courtesy of NASA

1. Near-Infrared Camera (NIRCam)
2. Near-Infrared Spectrograph (NIRSpec)
3. Near-Infrared Slitless Spectrograph/Fine Guidance Sensor (NIRISS/FGS)
4. Mid-Infrared Instrument (MIRI)

The primary mirror is over 21 feet (6.5 meters) in diameter. The sunshield is about 69.5 feet x 46.5 feet (about 21 meters x 14 meters), comparable to a tennis court.

Approximately 13,700 pounds

-370 degrees Fahrenheit (Below 60 kelvins)

Source: NASA

I started a little over 20 years ago on what was then called The Next Generation Space Telescope, and it's now called the James Webb Space Telescope. I got brought on to be really what amounts to what they call the telescope manager, or the optical telescope element manager. It involved the whole telescope, all the 18 primary mirror segments and the secondary mirror.

When I started we hadn't even selected who the prime contractor was, what technologies were. We still had three technologies we had to develop. So the first few years were technology development. Then we brought on the main contractor and a whole series of subcontractors. I was really the lead NASA person for that whole effort for these 20 years, getting it built, getting it tested.

NASA actually led the testing of the telescope. So that was a big challenge, testing something this big at cold temperatures. And now I'm helping to lead the team that's aligning the telescope in space. It's been the complete end to end NASA leadership for the telescope.

AK: The James Webb Space Telescope is the most sophisticated “eye in the sky,” so to speak, that NASA has ever launched. You not only were instrumental in designing the optics that enable the telescope to “see” but you’re also, in a sense, the eye doctor who can diagnose and correct any problems that may occur with its vision. Would you agree with that description?

LF: It's not a bad description, actually. You know, typically with a large reflective telescope, the pupil is the primary mirror. So our large 18-segment primary mirror is the pupil of the system. That's where we have the ability to correct. We have all these actuators on the primary mirror and each of those mirror segments has seven actuators. And so we can actually deform it, just like your eye can deform.

The main feature of the James Webb Space Telescope is this expandable, 6.5 meter (21 feet 4 inch) primary mirror that’s designed to capture light from some of the faintest objects in the universe. Photo courtesy of NASA

It's one thing to align a lens or a single mirror. But when you have a primary mirror that's segmented, those segments have to align to each other to a fraction of a wavelength of light. Otherwise the different wavelengths would interfere with each other, and our images would be full of interference. That's a unique problem that we have. But once we align that system, which is our hard problem, then we look at it every couple of weeks to keep track of how stable it is. And if things do start to migrate in some way, you know that they aren't perfectly stable, we have actuators that can adjust it. And so we sort of do these little eye exams very frequently, and then we can update it and tweak the prescription.

AK: Is an optical prescription for a space telescope anything like an optical prescription for a pair of eyeglasses or contact lenses, and if so, how is it similar? Do you measure optics in diopters, like in ophthalmics?

LF: There is some overlap. I'm not an expert on eyeglasses. But the big thing with eyes is power, you know, diopters. As time went on, [ophthalmic optics scientists] got smarter and realized they could correct astigmatism. Power and astigmatism are two of the most important aspects of the shape of our primary mirror.

We use the Zernike polynomial to represent the optical surface. Within that polynomial, the first order terms are power and astigmatism. And there are more terms, like coma. We care about higher order polynomials to describe our surface, but the first few terms are completely overlapping with what you do with eyeglasses.

AK: You’ve had some difficulties with your own vision throughout your life. Can you tell me what that’s about, and how it may have impacted your work as an optics scientist?

LF: I was probably four or five years-old when they tried to put a patch on my good right eye to help strengthen my weak left eye. But by the time they did it, it was a little too late. Once the nerves formed it had gotten to the point where they couldn't optically fix it. I think it’s called amblyopia.

AK: That’s what it sounds like.

LF: I actually am legally blind in my left eye. It's one of the reasons I got involved in optics. I have like 20/500 vision in one eye. My stereoscopic binocular vision, which I learned about later, was different than everybody else’s.

As I was growing up, I was always very interested in understanding how I could do depth perception and how the eye worked and whether there was a way that I could do something to help my eye. It's one of the reasons I studied optics.

There's definitely overlap between ophthalmology—how you deal with eyes—and how you deal with telescopes. You have a pupil in your eye and on a telescope. The primary mirrors in the telescope and way the eye works are related by optics.

It's funny because at NASA, when you work on the Space Telescope, most of the people there grew up interested in astronomy, that was their dream. But I just grew up interested in optics. When I was in high school, Star Wars came out. I got really interested in lasers, and I wanted to build a laser. That was a dream of mine. So there were two areas of optics that really interested me, and that was really the motivation.

How the Webb Telescope and a LASIK Surgery System Benefitted from a Collaboration Between NASA and Johnson & Johnson Vision

The overlap between space telescope optics and ophthalmic optics is most evident in the specialized technology used by both NASA and Johnson & Johnson Vision. The two science-focused organizations found an area of synergy, using the same innovative wavefront measurement technology for two different purposes.

Shack-Hartmann WaveFront Sensor, which measures wavefront aberrations in materials such as silicone wafer, contact lenses, IOL’s, and the eye, already existed within Johnson & Johnson Vision. In partnership with NASA, this same technology was applied to measure the polished surface of the mirrors on the James Webb Space Telescope.

Johnson & Johnson Vision’s iDESIGN Refractive Studio allows doctors to perform custom surgery.

Through this experience with NASA, Johnson & Johnson Vision accelerated the development, accuracy, speed and production of their proprietary iDESIGN Refractive Studio. iDESIGN is used to create a high-definition map of a patient’s eye to help guide a surgeon performing LASIK eye surgery to improve a patient’s outcome.

Johnson & Johnson Vision’s involvement with NASA began in 2017, after it acquired a company that had originally been spun off from the space agency in the mid-2000s. “NASA came to us with a problem,” explained Kristian Santana, principal electrical engineer, Johnson & Johnson Vision. “They needed the most precise measurement of these very important and amazing mirrors. We used our technology to try and solve that problem.”

NASA provided Johnson & Johnson Vision with resources that enabled the company to buy better cameras and computers, which it used to develop faster algorithms for real-time data processing and new optical path systems. The research not only helped NASA, but ultimately led to more accurate mapping for ophthalmic surgeons who were doing LASIK surgery, according to Santana.

“We have a much higher precision image, algorithm and data that our competitors, which allows doctors to perform surgery in which the outcomes are much better and are highly customized to each eye,” he added.