SAN FRANCISCO — In recent months, satellite photos have streamed into a former textile factory here revealing a build-up of potent Russian air defense systems in Ukraine, a serious new threat to NATO aircraft.

This is not a secret CIA facility, and the images didn't come from a billion-dollar surveillance satellite.

They were taken by private spacecraft — some the size of a loaf of bread — operated by Planet Labs, a Silicon Valley company that is leading a revolution in how humans glimpse Earth from space.

A short stroll from the downtown San Francisco headquarters of Yelp and LinkedIn, Planet operates the largest and least expensive fleet of satellites in history — the first to take pictures of the entire landmass of the globe, once a day, and sell them to the public. The company is part of a fast-growing commercial satellite industry that is democratizing insights once available mainly to people with Top Secret government security clearances.

In May, one of Planet's satellites captured a white plume of smoke from an illegal North Korean missile test, an image that rocketed through the next day's news cycle, undercutting President Donald Trump's insistence that the North Korean regime is negotiating with the U.S. in good faith.

A satellite image captured by Planet Labs shows a white plume of smoke from an illegal North Korean missile test on May 4, 2019. Planet Labs

"I think it's so important that the pictures don't lie," said Will Marshall, one of Planet's co-founders and a former NASA spacecraft designer. "The picture is what it is. And sometimes that can be inconvenient. But it also will help us to transition away from this post-truth world, towards one more grounded in facts."

The U.S. intelligence community is a Planet customer, but so are environmental groups, farmers, Wall Street traders and journalists. Planet's fleet of imaging satellites documents climate change, natural disasters, the growth of refugee camps and the number of cars in the parking lots of a national retail chain.

When floods inundated Western Iowa in March, state officials didn't have a handle on the severity of the damage until they saw Planet's overhead imagery. They say the data helped them better coordinate the response.

As last year's Camp fire raged across California, Planet's imagery helped officials decide where to send firefighting crews.

"Earthquakes, fires, floods, typhoons, tsunamis… We can help, because we have an image the day before, an image afterwards, to help responders quickly get in there," Marshall said.

The first spy satellites weighed nearly a ton and sent back pictures by dropping giant film canisters into passing airplanes. These days the most sophisticated government photo satellites can be the size of a school bus, and cost billions.

Marshall and his partners built their first satellite in a garage, applying the principles of the smart phone, stuffing a sophisticated camera and telescope into a rectangular box that weighs as much as a bowling ball.

Then they began blasting dozens of them into space at a time, piggybacking on commercial launches of larger satellites.

Planet won't say how much each one costs to make, except that it's "orders of magnitude" cheaper than traditional satellites.

Will Marshall and the founding members of Planet Labs in their garage office in 2012. Planet Labs

Commercial imaging satellites are not new; Americans have been looking at pictures from space of their houses on Google maps for years. But those pictures tend to be several years old, because there are only so many commercial satellites and they can only cover so much ground.

Planet has changed the game.

The company's satellites are lined up in orbit like a Saturn ring, taking a photo of the same spot at the same time at least once every 24 hours.

Never before have humans been able to document change on the planet's surface in quite this way. Marshall, who has given two Ted Talks on his technology, has a tag line for what he hopes this new imagery will mean for Earth: "You can't fix what you can't see."

The company's fleet of 140 satellites beams back 1.2 million images a day. That is so much data that customers are turning to artificial intelligence to make sense of it. That technology is in its infancy, which means this could be the beginning of a new age of insights about the Earth. One day, there could be enough satellites in orbit to provide total persistent overhead coverage — an-on demand photo of any spot on the earth at any time, weather permitting.

Other U.S. commercial satellite firms, including BlackSky and Maxar, operate more expensive satellites with better resolution than Planet's, but they don't have as many in orbit.

Planet's small satellites stay in orbit only two or three years before burning up as they fall form the sky. So the company is constantly building more of them, with newer and better technology.

"Last year we built roughly as many satellites as the whole world put together, outside of us, here in this little lab in San Francisco," Marshall said.

Will Marshall, one of the founders of Planet Labs, in the company's laboratory. NBC News

The company, which has yet to go public, is now valued at $2 billion.

As with any surveillance technology, the proliferation of commercial imagery can be put to ill use, by both governments and the private sector. The U.S. government limits the resolution of commercial satellite photos to ensure American spies still have the best pictures, and so the satellites cannot be used to snap close-ups of backyard sunbathers. But commercial satellites are not without privacy risks, and industry experts are only beginning to grapple with the implications. How long before a satellite photo of a straying spouse's car, parked where it should not be, is used in a divorce case?

Robert Cardillo, who until last year led the U.S. spy agency that processes satellite imagery, says the leaders of his field are now grappling with the same sort of influx of new data as the National Security Agency did when human communication migrated to the internet. And he wants to avoid an Edward Snowden moment — revelations about surveillance that alarm the public.

"We're awash in pixels," said Cardillo, the former director of the National Geospatial Intelligence Agency, or NGA, which has contracts with Planet and other private satellite companies. "Who controls the data? Where is it stored? How do you protect privacy? We have an opportunity to have this conversation now with the American people."

Biking and walking to work in downtown San Francisco, Planet's hoodie-and-jeans-wearing employees argue that their products are not designed for spying. They named their small satellites "doves" for a reason, Marshall said — they believe they are a force for good.

Planet Labs launches several of its small satellites. Planet Labs

A New Zealand livestock company is using Planet's imagery to monitor the grass in its pastures and send the cattle to the areas where the grass is higher. Arizona State University, the Hawaii Institute of Marine Biology and the University of Queensland partnered with Planet to map the world's coral reefs. Humboldt County, California has used the pictures to dramatically improve its enforcement actions against illegal marijuana farmers.

For Sarah Bidgood, who researches U.S.-Russia arms control issues at the James Martin Center for Nonproliferation Studies in Monterey, California, Planet's images have been invaluable, helping her track those new Russian weapons in Ukraine's Crimean peninsula, which Russia seized in 2014.

It's better for everyone if private analysts can study the world's geopolitical hotspots, she said.

"That's one of the things that Planet is doing that I think is so essential to the work of analysts like myself," Bidgood said. "It is placing information that gives us insights into granular changes on the ground into our hands. And that's what allows us to do good, nuanced analysis that can lead to good policy."