Susan G. Finley began working on rockets before NASA existed.

And now at age 79, instead of watching fireworks on the Fourth of July, she will be at her post in NASA’s Jet Propulsion Laboratory in Pasadena, Calif., 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, will monitor radio signals, waiting for one critical beep — a signal sent from Juno, the solar-powered planetary explorer — that announces 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 Canberra, 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. While agency officials will want to know what the tones mean in real time, Ms. Finley said the signals are often most important when something goes awry.