Each orbiter is only about the size of a coffee mug — and they cost less than $8,000 each.

WASHINGTON — NASA is an agency known for going big: big missions, big rockets, big budgets.

But nestled in California’s Silicon Valley is one NASA unit headed in the opposite direction. Its latest mission is tiny but has led to big expectations for the Small Satellite Technology Program.

In April, this NASA team launched three little satellites — each about the size of a coffee mug — aboard a test rocket from Wallops Flight Facility in Virginia. The probes shared two remarkable traits: All were built primarily from smartphone parts, and each cost less than $8,000.

The mission was simple. As with Sputnik — the world’s first satellite, launched in 1957 — the goal was to survive long enough to relay signals back to Earth.

But instead of the “beep-beep-beep” sent by Sputnik, these so-called PhoneSats (for phone satellites) had the brains to broadcast much more complex data, including pictures of Earth.

For six days, the probes zipped around Earth at about 17,000 mph and transmitted information about temperature and battery strength, as well as about 200 photos. Then the tug of Earth’s gravitational field became too much, and orbits that started about 155 miles overhead ended in flashes of fire as they re-entered the atmosphere April 27.

“I would say it was a success,” said Bruce Yost, head of the program.

Though his team had hoped the satellites would stay in orbit for a few more days, he said the six-day mission was more than enough to prove PhoneSats have a future — perhaps as low-cost weather satellites or Earth-observation platforms.

Up next are two missions designed to push the envelope even more. A fall launch will test the ability of a single PhoneSat to control its own spin in orbit. Then this winter, Yost and his team hope to send a “swarm” of eight PhoneSats to circle Earth and measure space radiation.

All nine could stay in orbit for a year or more.

The ultimate goal is to slash the cost of future satellites by using technology that’s sophisticated and cheap — in this case, modified versions of Nexus smartphones.

The design is “something that pretty much everyone can relate to by reaching down in their pocket and touching their phone,” Yost said.

Though no one at Ames Research Center — home to the PhoneSat program — could pinpoint the exact genesis of the idea, Yost recalled a question often asked by Pete Worden, the center’s director.

If a smartphone has “hundreds of times more processing speed and power than the computers used to land (the) Apollo (crew) on the moon,” Yost said Worden would ask, “couldn’t we find a way to use something like (a smartphone) on one of our missions?”

As it turns out, it’s not terribly complicated to convert a smartphone into a satellite — at least by rocket-science standards.

Yost said NASA chose the Nexus phones because information on how they work is readily available, and their “open source” Android operating system is easily manipulated. The biggest change, he said, was replacing the phones’ cell radios with versions that could communicate from space and adding a bigger battery.

The test runs are intended to test the limits of smartphone technology. The goal is to give future engineers a low-cost option for spacecraft that can transmit data about weather in space — or on Earth’s surface. The team is also working toward standardizing this type of satellite to bring costs come down even more.

“It does have that Silicon Valley startup kind of feel to it,” Yost said.

Still, the $14.9 billion global satellite market is likely to remain dominated by commercial and military satellites that carry tons of instruments, sensors and communications devices and can cost hundreds of millions of dollars to build, said Micah Walter-Range, an analyst with the Space Foundation, a major industry booster.

In the last decade, so-called “microsatellites” — weighing less than 200 pounds — have accounted for about a fifth of all satellite launches. Most, however, have been for research-and-development purposes and not commercial use, industry officials said.

“Short-term, I don’t see (PhoneSats) as something that changes the way the satellite industry works because the capability isn’t there yet,” he said. “But it’s exciting that people are experimenting and trying this.”

One worry is whether microsatellites can achieve and maintain the precise orbits needed for earthbound electronics. Another is, lacking a means of propulsion, that they could add to the growing problem of space debris in low Earth orbit — as they won’t be able to steer themselves out of the way of other spacecraft.

Even so, NASA and industry officials say they may be useful as weather-observation outposts. Officials at the National Oceanic and Atmospheric Administration and NASA say the number of Earth-watching satellites — key to forecasting hurricanes and other major weather events — will drop from 110 in 2011 to 30 or fewer in 2020 as aging spacecraft fail and aren’t replaced. Some type of microsatellite could help plug that hole — especially because the price tag of one of these small satellites can be less than that of a single part on larger NASA probes.

“We’re at the start of something here,” Yost said, adding: “We’re not sure of the final answer.”