When Susan Finley started charting the trajectories for rockets in January 1958, NASA didn't formally exist.

Finley was employed by the Jet Propulsion Laboratory (JPL) at the time, working as a "human computer." She, like other women who worked at JPL, did the trajectory calculations for rocket launches by hand.

NASA was officially formed in July 1958, thanks to the National Aeronautics and Space Act, and by December, it had assumed control of JPL, a military contractor managed by Caltech. Since then, Finley has been an employee of NASA.

With almost 60 years of service under her belt, Finley is the longest-serving woman at NASA.

'I love numbers, much better than letters'

Susan G. Finley in 1957Finley attended Scripps College in Claremont, California, with the intention of majoring in art and architecture. It didn't pan out, however, as she "couldn't learn art," according to an interview she gave to the New York Times.

She dropped out after three years and applied for a filing clerk job with the now-defunct airplane and rocket manufacturer Convair in Pomona. After the typing test, they told her that the position had already been filled, but they asked her how she felt about numbers.

"I said, 'Oh, I love numbers, much better than letters,'" she recounted to the LA Times. "So they put me to work as a computer."

This was in the mid-1950s when "computers" were mostly women who did complex math problems by hand regarding things like wind tunnel tests, rocket trajectories and the like. Many of these women, according to JPL, didn't have degrees; they were simply very good with numbers.

Finley worked at Convair for about a year before she decided she needed something new. She had married in 1957 and moved to San Gabriel, and she wasn't a fan of the commute. Her husband, a recent graduate from Caltech, suggested she apply for a job at JPL, which was much closer to home. JPL needed a computer, and Finley was hired.

"You just wrote across the top a step-by-step breakdown of how to use the numbers and then down the other side were the numbers you were going to have to try," Finley explained to the New York Times. "You just went across, plugging in and clanking away. And then at the end, you gave them the piece of paper with all the answers on it."

A few days after she was hired, JPL launched Explorer 1, America's first-ever satellite.

"What I remember was this great big sheet cake that we all got," Finley told the LA Times. "And there weren't that many people working at JPL [at the time] that they could use just one sheet cake."

In and out and in again at JPL

NASA's Jet Propulsion Laboratory in Southern California. NASA's Jet Propulsion Laboratory in Southern California. (Photo: NASA JPL)

Finley's best-remembered contribution in her early years at JPL is connected to Pioneer 3, a 1958 probe that was supposed to circle the moon and then enter solar orbit. It failed to do that. Finley was asked to calculate the probe's velocity data after the digital computer that was supposed to do it failed.

"I punched this data into the Frieden [calculator] as Al Hibbs relayed it to me from his telephone connection with the receiving antenna. I went home around 6:00 a.m. after everyone realized that it hadn’t reached escape velocity, so it wasn't going to leave orbit," she told NASA. "My husband was up watching the news. They had a little blackboard with the numbers on it I had calculated. I said, 'That's my number!'"

Finley stayed with JPL for 2 /12 years, leaving so her husband could began graduate studies work at the University of California, Riverside. Between jobs at the time, Finley took a week-long course offered by Riverside on Fortran, a programming language developed in the 1950s by IBM intended for scientific applications.

After her husband finished his master's degree, Finley returned to JPL in 1962, this time with a programming language in her skill set. She was one of the few people at JPL who even knew Fortran.

Finley left JPL again, only a year later, to take care of her two sons. She returned for good in 1969 and found that more women were working at JPL than when she left, and that the human computers had become human programmers.

By the 1970s, female teams of programmers, previously kept separate from the male engineers on the same mission, were fully integrated with one another.

"The men always, from the very beginning, treated us as equals," Finley said to the LA Times. "We were doing something they couldn't do and that they needed to go forward with what they were doing."

Programming deep space technology

Since the 1980s, Finley has worked as a subsystems engineer and software tester for NASA's Deep Space Network (DSN). The DSN tracks and communicates with NASA's various unmanned spacecrafts and probes, sends commands, transmits software updates and gathers data. The DSN also works in conjunction with other countries' space agencies.

Finley's DSN work included collaborating with the USSR and France during the Vega program, a series of Venus-centric missions. One of the missions was the Venus Balloon Project. This involved two Russian probes speeding toward Halley's comet while deploying two balloons into Venus' atmosphere to collect data on the planet.

Finley wrote the program that automated the movements of the DSN antenna, and the antenna had to aligned precisely with the spacecraft to receive any data from it.

"I can remember when we saw the first signal in the darkroom, I actually jumped up and down because I was so happy," Finley told the LA Times.

Making music in space

In the 1990s, Finley worked on the Mars Exploration Rover missions by developing a program in which the rovers would send back musical tones after each stage of the craft's descent through the Martian atmosphere. The software would receive and interpret the tones so that the project's engineers would know what was happening.

This process was used for the Pathfinder landing in 1997, but it was left out of the Climate Orbiter and Polar Lander missions, both of which were lost in 1999. NASA's attempts to figure out what went wrong with both were hampered by the lack of Finley's tones. The tones were returned to the Martian landing process in 2004.

Finley's contributions to these landings were rarely acknowledged by the press, but she just laughs it off.

"They're always focused on the control room at JPL," she said to NASA. "People really doing the work don't get on TV."

A job not without controversy

In 2008, JPL reviewed all job and pay listings and changed Finley from a salaried engineer to an hourly engineering specialist since she lacked a bachelor's degree. Finley's overall pay did not change, and she is eligible for overtime, but she has to clock in and out.

"It's a demotion," she said to the New York Times. "No one wants a demotion. We want to be treated like we deserve. But it's true. I don't have a degree."

"I think I'm kind of smart, maybe," she added. "I just hate school. I love work.”

And love to work she does. Finley has no plans to retire, "unless things start to get really boring," she told NASA.

Inset photo of Finley in 1957: NASA