With dozens of NASA employees looking on and online viewers tuning in from across the country, engineer Allen Chen delivered two words ­Sunday night he won’t soon forget.

“Touchdown confirmed,” Chen announced shortly after 10:30 p.m. West Coast time, as those gathered in a Pasadena, Calif., control room burst into celebration.

Curiosity, the space program’s $2.6 billion rover, had landed on Mars.

The touchdown capped an eight-month flight and a decade of work for Chen, a graduate of the Massachusetts Institute of Technology, who led the team responsible for landing the rover.

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“I’ve been dreaming about that for a long time,” Chen said.

Chen traces his interest in space back to elementary school. After growing up in Pennsylvania, he came to Cambridge in 1996 to attend MIT as an undergraduate.

It was there that Chen decided to become an engineer ­instead of a researcher.

“Turns out I’m better at building things than trying to figure out the secrets of the universe,” he said.

With Curiosity, he found a way to help with both. The rover will spend two years combing the surface of Mars, and it could yield clues about whether life ever existed on the planet.

Curiosity is the most sophisticated of the seven spacecraft NASA has landed on Mars. It packs 10 scientific instruments that will gather data about the surface of the planet.

But all that equipment makes Curiosity far larger than previous Mars rovers. It weighs in at five times the weight of Spirit and Opportunity, two rovers that landed separately in 2004.

Curiosity’s size created unprecedented challenges for Chen and his colleagues as they worked to engineer a smooth landing.

Chen’s team grew from about a dozen in 2002 to more than 1,000 once the project shifted from its design phase to construction.

Their work culminated Sunday night as they monitored Curiosity’s final descent, which included enough hazards to earn the nickname “the seven minutes of terror,” a reference to the final harrowing segment of the rover’s voyage.

Then, in a span of 15 seconds, three separate notifications reached Pasadena confirming a successful landing. Chen delivered his much-
awaited announcement, and anticipation quickly gave way to jubilation.

“It was definitely a rapid ­escalation to euphoria and ­relief,” said Chen, who lives near Pasadena with his wife, whom he met at MIT, and their two children.

The landing took place after 1:30 a.m. on the East Coast, but that did not stop David Miller, the MIT professor who served as adviser for Chen’s master’s thesis, from tuning in to the live stream from his home in ­Sharon.

Miller, who teaches aeronautics and astronautics, ­recalled Chen as a standout student who earned the respect of his classmates during a yearlong design and construction class project.

As Chen and a dozen classmates created an instrument for use by the International Space Station, certain challenges arose, Miller recalled. When that happened, classmates repeat­edly asked Chen to talk with the professor, and Chen’s working style impressed him, Miller said.

“Allen’s not shy, and he’s very focused,” Miller said. “He wants to solve whatever’s impeding the team as soon as possible.”

In class, the work of Chen’s team paid off. The prototype they developed led to the creation of a complex testing instru­ment currently in use on the International Space Station.

“Curiosity is not his first piece of hardware in space,” Miller said.

Though he marveled at the precision needed to land Curiosity, Miller said Chen’s success did not surprise him.

The professor praised his former student for his role in what he called a “seemingly ­impossible task.”

“It puts an exclamation point at the end of the sentence that says the US is innovating and accomplishing bold tasks,” he said. “That’s something that we sorely need.”

With the landing complete, Chen will shift his focus to documenting what happened during the rover’s descent.

Money for Mars missions in the near future remains uncertain, but Chen said he wants Curiosity’s voyage to help ­future engineers as much as possible. “I want to make sure, whether it’s us or someone else down the line, they have everything they need to know,” he said.