The Art of Lunar Mapping: ACIC’s Patricia Bridges Airbrushed Americans’ Path to the Moon

The drawings of the moon's Copernicus crater made by Patricia Bridges under the stairs at ACIC eventually became the Copernicus Lunar Astronautical Chart, or LAC 58. Photo courtesy of Patricia Bridges/Lowell Observatory.

The first known map of the moon was created in 1609 by English mapmaker Thomas Harriot, with the help of his telescope. By the late 1950s, as Americans warily eyed the skies for the Soviet's Sputnik satellite, the newly formed U.S. National Aeronautics and Space Administration asked ACIC, which would later become the National Geospatial-Intelligence Agency, to make a new set of maps.

These maps needed to be much more detailed than any produced by Harriot or his selenographing successors. These maps needed to provide NASA the information needed to allow a human to land on, explore and return from the moon.

By 1959 plenty of photographs existed of the moon's surface, taken through telescopes much more powerful than Harriot's, but photographs don't have coordinates. They don't indicate how wide a plain is, how deep a crater, or how tall a ridge. If the United States was going to successfully land a human on the moon, ACIC needed to create lunar charts more detailed than any made before - and quickly.

Illustrators like Patricia Bridges were a vital part of ACIC's moon map-making process, using pens and airbrushes to fill in details of lunar craters, ravines, mountains and plains. Bridges was known to be the best at her craft. Photo courtesy of Patricia Bridges/Lowell Observatory.

By 1960 ACIC's special projects lead Bill Cannell, one of Bridges' supervisors, is out touring the United States in search of the best telescope to view the surface of the moon. Or, more precisely, the best telescope to view the surface of the moon that's available.

He finds one in Arizona at Lowell Observatory in Flagstaff.

Cannell plans for a three-person ACIC team - himself, Bridges and a cartographer named Jim Greenacre -- to move from St. Louis to Flagstaff, where they can photograph, observe, sketch and chart, all in the same place.

Bridges had come to ACIC in 1956, not necessarily out of a passion for mapping. While in art school at Washington University in St. Louis, Bridges, a painter, had worked restoring murals in St. Louis' historic Old Courthouse. "They didn't think any women would do that, because you have to climb around on scaffolding, and you had to climb way up in the dome," Bridges will say in 2015. "I loved it."

She'd heard there was a place in St. Louis, a couple miles south of the Old Courthouse, where the government hired art majors to make maps, so she'd applied. She was assigned to ACIC's special projects team and eventually ushered under the stairs with a stack of lunar photographs.

Bridges, who had grown up across the river from St. Louis in Alton, Illinois, is excited about the move to Arizona. She and her husband, Al, had honeymooned in Flagstaff, and both had "fallen in love" with the area, she'll later tell historians.

ACIC public affairs officer Mel Kramer sketched this drawing of Patricia Bridges while she made observations at the telescope for an article he wrote in the ACIC newspaper, Orienter.

Why did Cannell choose Flagstaff? For one, Lowell's 24-inch Clark Refractor telescope is "ideal for moon-mapping," said Kevin Schindler, historian at Lowell Observatory. The Clark wasn't too big or too small - it provided just the right power, or magnification, for viewing the lunar surface, Schindler said.

Second, Flagstaff sits at a high elevation -about 7,200 feet above sea level. Air movements in the atmosphere can distort images viewed through a telescope; higher elevation means less air to see through and less distortion, said Schindler.

And, most important, the telescope was available. "The Clark telescope wasn't being used too much at that point for research," Schindler said. "When the observatory was built, there was virtually no light pollution to interfere with the telescopes, but as Flagstaff grew, the site was no longer ideal for viewing. But the moon is so bright, light pollution doesn't matter."

It was perfect.

Patricia Bridges captioned this photo of her in the ACIC office at Lowell Observatory: "Me in my corner in the foreground and my drawing table on the left. My tank of air in the corner." Photo courtesy of Patricia Bridges/Lowell Observatory.

The ACIC team that first arrives at Lowell in 1961 consist of only three people. Bridges, who goes by "Pat'" is the only woman on the team. Those who don't know her often assume ACIC's "Pat" is a Patrick. She surprises more than a few.

Each person has a role: Greenacre takes lunar photos and provides lunar observations to Bridges, Bridges draws the maps, and Cannell oversees the project.

Photographs provide the foundation for the team's lunar charts, but they also film movies of the moon. Each recording contains hundreds and hundreds of still images, which allow the team to choose photos least distorted by air turbulence. The best photos are sent to ACIC St. Louis, where the photos are "rectified," or altered to make allowances for the curvature of the moon's surface and other distorting factors, and then sent back to the Lowell team.

But photographs aren't enough to capture the level of detail ACIC needs. The map-making team also spends nights at the Clark telescope observing the moon's surface, because a human can see more through the telescope than with photos - "about 4 times as much," Cannell tells a reporter for the Arizona Daily Sun. The ACIC team discovers thousands of small craters on what previously had been thought of as a smooth surface - important details if you're choosing a landing site.

Cannell and Greenacre sit at the telescope with photos of the lunar surface, filling in details photographs miss. Their notes go to Bridges, who also often makes observations herself to confirm or clarify her team members' notes. Sessions at telescope often last several hours at a time, depending on how much of the area the team is charting is illuminated. "If it was illuminated, we were there," Bridges said in 2015.

ACIC public affairs officer Mel Kramer writes about his experience visiting the ACIC team at Lowell for ACIC's publication, Orienter. "Separate, small sections are brought into focus [through the telescope], and observations on it are annotated on corresponding sections of photographs," Kramer writes. "The next day, these annotations are interpreted and airbrushed into the master shaded relief drawings. In that way, literally, pore by pore, the moon's portrait is being painted."

It's winter when Kramer visits, and the dome that houses the telescope is not heated. Bridges wears earmuffs and a jacket to work. Kramer notes the ACIC team dresses like "polar explorers."

Patricia Bridges (left) hikes in the snow around the grounds of Lowell Observatory. Lowell is located in Arizona, which is typically associated with hot weather. However, in Flagstaff, Ariz., the average low in January is 11 degrees Fahrenheit. Because the telescope dome was unheated, it could be a very cold environment for ACIC's Lowell team to work. Photo courtesy of Patricia Bridges/Lowell Observatory.

Structures that house telescopes weren't, and still aren't, heated, said Schindler, the Lowell historian. That's because warm air rising from the top of the dome, where the telescope juts out to the sky, would cause more air turbulence, and therefore more image distortion, than might naturally occur.

The average low in January in Flagstaff is 11 degrees Fahrenheit and temperatures are typically at their lowest at night - the best time for viewing.

Fortunately, Bridges could draw in the heated ACIC office, a structure a few minutes' walk from the telescope. While much of modern map-making is digital, ACIC's lunar charts had to be hand-drawn. Artists such as Bridges, called scientific illustrators, were a vital part of the map-making process, using pens and airbrushes to fill in details of lunar craters, ravines, mountains and plains.

More illustrators joined the ACIC team at Flagstaff as the team of three grew to a team of 15 by 1965, but Bridges was widely known to be best at her craft, Schindler said.

"Like a stonemason, everyone has their own particular technique," Schindler said. "Patricia Bridges was very accurate in her drawings and had a good eye for detail. Her charts were highly regarded."

Patricia Bridges captioned this photo of her in the ACIC office at Lowell Observatory: "Jim Greenacre at the supply cabinet and yours truly (legless) at the filing cabinet across from my corner." Photo courtesy of Patricia Bridges/Lowell Observatory.

In 1963, a dozen or so American astronauts, including Neil Armstrong, come to Lowell for crash-course in lunar geography - which, to Bridges, feels akin to a visit from rock stars. The astronauts, the same ones on TV, who will someday visit the moon, looking at pictures she drew - incredible!

Bridges isn't the only one starstruck by the American astronauts. The entire United States is caught up in the drama, the adventure, to get an American on the moon.

The government starts offering Bridges' charts to the public for purchase; anyone can buy one by sending $3 to the Government Printing Office. Soon Bridges' work is on display in homes and offices, across the United States. It is pored over by both professional and aspirational scientists, astronauts and cartographers.

With the charts created by Bridges and her team, NASA selects a landing spot for the Apollo 11 astronauts: a flat location in the area known as the Sea of Tranquility.

In July 1969, Bridges watches with the rest of the United States as Neil Armstrong, the astronaut who had visited her office and looked at her charts, became the first human to step foot on the moon. She's amazed - and proud. She is part of something really important, really special.

By the next year, Bridges will take a new job, with the U.S. Geological Survey, charting the United States' next projected destination in space: Mars.

Bridges' daughter, Laura Ball, was 3 years old during the moon landing. Growing up in Flagstaff, Ball understood her mom did something special.

Back then, it was still a bit of a novelty to have a mother with a career, Ball said. Ball remembered her mother came to career days at school to talk about her work. Bridges brought home Mars rock props, left over from exercises with potential Mars rovers and painted dusty red. They were the subject of one of her favorite practical jokes. "She would pretend they were heavy, and carry them to people," Ball said. "Then, once she handed the rocks to them, they'd realize they were Styrofoam and weigh next to nothing."

Ball said even as a small child, she noticed the pride in her mother's voice when Bridges talked about her work. "It was in the way she carried herself," Ball said. "She loved her job and was happy to show it off; not like in a bragging way, but teaching, in a way to inspire."

Bridges retired in 1992. In 2015, she told interviewers that the enthusiasm she developed for her lunar and planetary mapping work surprised her. "This work, which I never had any idea I would do as an art major, it turned out that it was just really fascinating to me," she says. "I felt very fortunate."

A painter helped show the way to one of humanity's most significant scientific achievements. Bridges passed away in 2021, and humans still haven't made it to Mars. But maybe future generations will - and will look back at Bridges' charts to help guide them.

Written by: Jessica Daues