Call it a Halloween "treat" -- as opposed to a trick.

On Oct. 31, an Orbital ATK Minotaur-C rocket blasted off from Vandenberg Air Force Base in California. Its cargo: a payload of 10 imaging satellites going into orbit for one of the biggest satellite companies you've probably never heard of: Planet Labs.

Planet isn't a household name just yet, but it's a name you'll want to get familiar with. Believe it or not, Planet operates the biggest commercial satellite constellation in space today.

Four satellites over Earth

Planet's Dove satellites now ring Earth, taking pictures daily. Image source: Planet Labs.

Look at all the pretty satellites!

If you look up in the sky at night, you'll see a lot of "stars" -- but not all of those stars are suns. Some are actually satellites circling at low altitude. All sorts of satellites circle the Earth today -- about 1,400 of them are operational (alongside tens of thousands more pieces of space junk). Of the constellations up there right now, Iridium's is probably the best known. Its 66 existing satellites (scheduled to be de-orbited) and 30 new "NEXT" generation satellites provide customers around the world with communications services in the air, on land, and at sea -- and Iridium has 45 more NEXT satellites on the way.

Other companies have proposed building bigger constellations of satellites. OneWeb hopes to put 720 satellites in orbit. Boeing plans to orbit more than a thousand, while Elon Musk's SpaceX has proposed -- get this -- a constellation numbering in excess of 4,400 satellites, all delivering Internet to the masses.

For the time being, though, those are just plans. Right now, Planet Labs has the largest satellite constellation in orbit.

"Planet" is the name, taking pictures of Earth is its game

In contrast to communications satellite constellations, both existing and planned, Planet puts satellites in orbit for the purpose of photographing ("imaging") the Earth. The company only set up shop six years ago, but it's already achieved its primary goal of being able to "image the entire Earth's landmass every day."

Last month's launch delivered six high-resolution SkySats (acquired with Planet's purchase of Alphabet subsidiary Terra Bella earlier this year), along with four of Planet's own Dove medium-resolution satellites. With these in orbit, Planet now boasts a satellite network of more than 180 medium-res satellites (Doves and older RapidEye birds), plus 13 of the high-res SkySats acquired from Alphabet.

The number is constantly changing as older satellites drop out of orbit and newer satellites are added, but Planet says it has about "200 medium[-]  and high[-]resolution satellites" in orbit today. At six times the size of Iridium's satellite fleet, this gives Planet "the world's largest fleet of medium[-] and high-res assets."

To put that in further context, satellite imaging company Digitalglobe has just five satellites in orbit -- bigger, more powerful, higher-resolution satellites, to be sure, but still offering nowhere near the coverage that Planet can provide.

What it means to investors

Admittedly, this is sort of bittersweet for investors. While it's possible for us to invest in Digitalglobe's constellation (through its Canadian parent company Maxar Technologies -- known until recently as MacDonald, Dettwiler and Associates), Planet Labs is, for the time being, still a privately held company, and unavailable for investment. Even so, Planet is a company worth keeping an eye on, and I'll tell you why.

With much of its constellation now in place, Planet says it is taking 1.4 million 29-megapixel images of Earth daily, covering 300 million square kilometers of the planet's surface. Over the course of the past six years, Planet's satellites have created a catalog including an average of 440 snapshot images, per location, of every location on Earth. That's an invaluable resource for tracking changes on the ground over time.

What Planet intends to do next is to use its accumulated catalog, plus new images as they come in, to "index physical change on Earth the same way Google indexed the internet." With total coverage of Earth's landmass, the company can, for example, keep visual tabs on the growth rate of housing stock in cities to gauge the health of the housing market, monitor traffic at seaports (generating information useful for shipping, railroad, and trucking investors) -- and multiple other uses too numerous to name. "Never before," says Planet, has any company been able to provide commercial imaging at this scale. Now that it is available, it will help companies to "gain smarter, more timely insights to solve our world's toughest challenges."

The companies that make the best use of this new source of data will be the companies we want to invest in tomorrow.

Suzanne Frey, an executive at Alphabet, is a member of The Motley Fool's board of directors. Rich Smith owns shares of Alphabet (C shares). The Motley Fool owns shares of and recommends Alphabet (A and C shares). The Motley Fool recommends Orbital ATK. The Motley Fool has a disclosure policy.