George R. Carruthers

Over the course of his long and distinguished career at the US Naval Research Laboratory (NRL) in Washington, DC, astrophysicist George R. Carruthers was both a role model for a life devoted to science and innovation, and a mentor whose science outreach programs had a profound impact on minority students.

The technologies Carruthers developed led to some of the most iconic and scientifically valuable images from NASA’s Apollo Moon missions. And his achievements also led to the Oval Office where, in 2012, President Barack Obama presented Carruthers with the prestigious National Medal of Technology and Innovation.

Carruthers died in 2020. He was one of the nation’s few Black physicists for most of his career.

One former high school intern, Jessye Talley, an assistant professor at Morgan State University, recalls especially Carruthers’ generosity with his time, and her ability to simply be in his laboratory and read the books on his shelves. Carruthers helped her write a research abstract and prepare a presentation for the National Technical Association—a formative experience for a teenager contemplating a career in science.

“When I look back, I think about how many people get the chance to work with someone [like Carruthers], to be mentored by him and work on something, you know, see his contribution.” As a Black woman and now herself a scientist, “representation matters,” Talley says of the opportunity to work with a high-achieving researcher who was also Black.

But those who knew him say Carruthers was foremost a scientist.

“He was an experimentalist who worked on the most compelling issues of the day,” says physicist Robert Meier, who worked with Carruthers at NRL starting in the mid-1960s. His far-ultraviolet (UV) imaging devices led to the first UV images of the Earth’s upper atmosphere, detection of molecular hydrogen in interstellar space, far UV images of comets like Halley’s and Kohoutek, as well as new views of stars and solar systems otherwise invisible to the naked eye.

George Carruthers (right) and William Conway, project manager at the Naval Research Institute, examine the lunar surface far-ultraviolet camera/spectrograph. Credit: Naval Research Laboratory

“He was a great teacher,” says engineer Tim Seeley who worked with Carruthers in the 1980s. “He taught me a great deal about instrument design. He was a leader in that he performed so many of the design tasks himself. He wore many hats, and he passed some of that on to me.”

Carruthers’ work at NRL got underway in earnest with his 1966 patent application for an “Image Converter for Detecting Electromagnetic Radiation Especially in Short Wave Lengths.” He was awarded the patent in 1969; the invention became the wellspring for many imaging devices to follow from the Carruthers laboratory at NRL, all focused on detecting radiation in the far UV.

According to Carruthers’ patent, the camera “provides an internal optic image converter in which parallel light enters a front opening of the converter tube and is focused by an internal mirror with the tube structure on the photocathode. Electrons are emitted from the photocathode due to the incident light and are accelerated in an axial direction along the length of a tube.”

A magnet surrounding the tube focused the electrons onto a phosphor screen, converting the electrons to light for capturing optical images, or the electrons could be recorded directly on a nuclear track plate or film.

“That was a major breakthrough in camera systems,” says Meier, referring to the dual capabilities for imaging and spectroscopy using electrons instead of photons.

A 50-lb, gold-plated version of this camera system was carried aloft to the Moon on the Apollo 16 mission, creating the first and only Moon-based space observatory.

Unless it was destroyed by an ascent module, the camera should still be on the Moon, says David DeVorkin, senior curator at the Smithsonian Institution’s National Air & Space Museum. A replica of Carruthers’ camera system is on display at the museum’s Udvar-Hazy annex near Washington’s Dulles International Airport.

George R Carruthers' patent for the Image Converter for Detecting Electromagnetic Radiation Especially in Short Wave Lengths. Credit: Naval Research Laboratory

As a Carruthers biographer, DeVorkin says he is intrigued by one of the inventor’s key insights for the image converter.

“George’s design didn’t use transmissive cathodes, he used reflective cathodes, and I still do not know where he got that idea,” DeVorkin says. “But using the reflective photocathode design made it much more reliable because the transmissive [cathode] kind of scrambled the signal. [Carruthers] was able to take reliable spectra of course, but he could also take [optical] images. Among the most important were images of the geo corona of the Earth and showing how it varied with solar activity.”

Former colleagues tell Photonics Focus that Carruthers never discussed being a Black physicist and was circumspect about his personal life. They describe a friendly but shy man completely absorbed by his work. They say he was the NRL researcher who flipped the lights on in the morning after bicycling to work, and then turned them off at night, the last person to leave the laboratory.

Interested in astronomy since childhood, Carruthers went on to earn a bachelor’s degree in physics, a master’s in nuclear engineering, and a PhD in aeronautical and astronautical engineering at the University of Illinois at Urbana-Champaign.

According to an obituary published in Physics Today and written by former colleague, astronomer Harry Heckathorn, Carruthers, while completing his doctoral dissertation on atomic nitrogen recombination in 1964, was invited to give a colloquium at NRL. Subsequently, he became the lab’s first E. O. Hulburt Postdoctoral Fellow and accepted a full-time staff position there in 1967.

Thomas Edison’s advocacy led to the founding of NRL, Heckathorn notes, and the lab is a legacy of the great inventor’s belief in the benefits of support for unfettered scientific curiosity.

It was the perfect atmosphere for Carruthers’ creative mind, Heckathorn says. Along with the freedom to explore new ideas, “We had machine shops for metalworking, facilities for anodizing parts, an optical fab shop. We had test facilities for space applications—shake, rattle, and roll the payload before it goes on the rocket. If you wanted something made, you could just go over and talk to the machinist.”

But along with his pioneering instruments and the images they captured, Carruthers’ legacy will always also include the next generation of Black scientists he inspired.

“When you’re in that position to be able to sway someone who really is interested in science, and just keep on being that voice,” Talley says, “I think that’s what [Carruthers] showed us. Show up and be there and talk about what you’re doing. And then it makes a difference. Significantly.”

William G. Schulz is Managing Editor of Photonics Focus