Google Earth / DigitalGlobe

A satellite image of Yucca Lake in Nevada, acquired on March 13, shows what appears to be a Predator or Reaper drone being towed at a restricted airstrip.

A satellite photo that appears to show a military-style drone at a secret Nevada air base is stirring up a buzz on the Web, but don't worry: The imagery you're seeing on Google Earth is tweaked to avoid compromising national security.

The picture, which became the subject of multiple news reports over the past week, demonstrates the power of 24/7 satellite surveillance. It focuses on a dry lakebed, known as Yucca Lake, which has been used for secret projects for decades. Like the better-known Area 51, this patch of the desert (sometimes referred to as Area 6) is closely watched by amateur aficionados. It's been seen as a test site for unmanned aerial vehicles like the MQ-1 Predator, the MQ-9 Reaper and the RQ-170 Sentinel for at least the past three years.

Google / Digital Earth

A close-up taken from orbital imagery shows what appears to be an unmanned aerial vehicle sitting out at the Yucca Lake airfield.

RQ-170 Sentinels are in the news because the state-of-the-art spy drone was downed in Iranian territory, representing what appears to be a serious security setback for the U.S. military. The Nevada picture on Google Earth, which was acquired in March by one of DigitalGlobe's satellites and fed into the Google Earth system, doesn't show a Sentinel. It looks like one of the less advanced, less swoopy Predators or Reapers. Of course, there's always a chance that the craft is a decoy. (We are talking about secret air bases, after all.)

Flight Global's website, which published the image last week, speculated that the airfield is being used by the CIA to test hardware and software for its classified aerial operations. Since then, other news reports have been asking whether Google Earth is compromising national security.

U.S. satellite operators have worked out agreements with the federal government that govern the resolution of imagery made available through public databases, and you can imagine that the public images are fuzzier than the satellites' full capability. There can also be restrictions on what areas are targeted during particular times.

Potentially embarrassing images can surface, of course — such as pictures of drones in an area of Pakistan where the Pakistani government said there were no drones. And the concerns could become more acute as other countries launch imaging satellites that don't have to follow U.S. rules. But the Yucca Lake photo doesn't tell anybody who has been paying attention — including the bad guys — anything they didn't know already. The fact that the picture is still available, almost a week after it was thrown into the spotlight, suggests that national security has not been endangered.

I've made inquiries with the public relations folks for Google and DigitalGlobe, and if I hear anything back I'll update this item.

The Google Earth image serves as today's offering from the Cosmic Log Advent Calendar, which features views of Earth from space every day from now until Christmas. Check back for another image on Tuesday, and check out these previous offerings:

• The full Cosmic Log Space Advent Calendar
• Dec. 1: An ornament in outer space
• Dec. 2: The masses in Mecca
• Dec. 3: Santa's shrinking domain
• Dec. 4: The monster of Madagascar
• Dec. 5: Antarctica stripped naked
• Dec. 6: Streaking for home
• Dec. 7: Pearl Harbor from above, 1941-2011
• Dec. 8: The rise and fall of the Dead Sea
• Dec. 9: How an eclipse dims Earth
• Dec. 10: Psychedelic storm
• Dec. 11: Beauty of the Inland Sea
• Hubble calendar, from The Atlantic's In Focus
• 2011 Zooniverse Advent calendar