PASADENA, California • She began working on rockets before Nasa existed. And now, at age 79, instead of watching fireworks as the rest of the country celebrates independence, Ms Susan G. Finley will be at her post in Nasa's Jet Propulsion Laboratory in Pasadena, California, waiting for confirmation that the latest of its space adventures has succeeded.
Ms Finley, an engineering specialist for the Deep Space Network of radio telescopes who monitors radio signals, is waiting for one critical beep - a signal sent from Juno, the solar-powered planetary explorer, that says it has finally reached Jupiter, the largest planet in the solar system, after a five-year journey.
"It's a hard signal to track," Ms Finley said. "We do think it's going to work."
If everything goes right, her computer will pluck tones out of the data sent by Juno and received by an array of four radio telescopes in Australia. Those tones will be translated and displayed as 36 reassuring messages over four hours.
"It has real words in it about what's happening," Ms Finley said.
Confirmation of whether Juno, the only solar-powered spacecraft ever dispatched to the outer solar system, has successfully placed itself into polar orbit around Jupiter is not expected until 11.53am today (Singapore time).
Ms Finley said the signals are often most important when something goes awry.
Tones are useful when a spacecraft's main antenna is not pointed at Earth, as is the case with Juno during the phase in which it fires its engine to get captured by Jupiter's gravity.
The smaller, weaker antenna can transmit only simple tones as communication.
This is a far different job from January 1958 when Ms Finley first walked into the Jet Propulsion Laboratory.
One of the female space pioneers featured in the book Rise Of The Rocket Girls by Nathalia Holt, Ms Finley started just before the launch of Explorer I, the first satellite the US successfully sent into space. Six months later, Nasa was created, and soon the laboratory, which had performed rocketry work for the army, was transferred to Nasa to focus on sending robotic probes to explore the planets.
Ms Finley was not an engineer. She had taken some mathematics classes and, with an affinity for numbers, she literally became a human computer. Electronic computers were still rare and expensive, so engineers - invariably men - handed off the equations they needed to have solved to a computer, almost always a female employee.
"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," Ms Finley recalled. "And then at the end, you gave them the piece of paper with all the answers on it."
She left for six years to raise two sons until the younger one entered nursery school, and then returned in 1969, picking up computer programming and becoming an engineer. Over the years, she also worked as a test engineer and then an engineer on the Deep Space Network. Nasa used the simple tones technique in landing Mars Pathfinder in 1997. But it left them out for two later Mars spacecraft - Climate Orbiter and Polar Lander, which were both lost in 1999.
Investigations were hampered without the data supplied by the tones and Nasa resumed using the tones for its next Mars mission - the two rovers Spirit and Opportunity, which landed in 2004.
Ms Finley has no plans to retire. When the next rover lands on Mars in 2021 she hopes to be at her post.
NEW YORK TIMES