Earth's Water Cycle Measured via Giant Antenna

The Soil Moisture Active Passive satellite will help forecast drought and climate change

Join Our Community of Science Lovers!

The atmosphere inside mission control at Vandenberg Air Force Base in California this Saturday was electric as scientists watched their life's work—a NASA satellite—slowly lift off on a Delta 2 rocket. It was the third try; the first attempt, Thursday, was scrubbed due to high winds and the second, on Friday, due to minor rocket repairs.

The rocket's cargo was precious. The satellite—SMAP, or the Soil Moisture Active Passive—has been in development for more than two decades. Once in orbit 426 miles above Earth, SMAP would measure the moisture contained in soil, which is key to learning how the planet's water cycle is working. It would also track the soils of the Northern Hemisphere and reveal which regions are sequestering carbon and helping abate global warming (ClimateWire, Jan. 20).

As the countdown began, SMAP was safely nestled in the rocket's fairing. The spacecraft recounted its feelings in those final seconds to ClimateWire via Twitter.


On supporting science journalism

If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.


"As the spacecraft, it was dark inside my fairing & I was eager to launch so I could begin my mission to do science," it (or its social media officers) wrote.

Within a few seconds, Delta 2 was an orange glow in the sky, carrying the satellite at 16,850 mph, fast enough to escape Earth's gravity and get into orbit.

Then, about 50 minutes after launch, SMAP separated from the rocket. With the blue-and-white Earth as its backdrop, the satellite opened up its twin solar arrays and entered orbit.

Career-centered efforts
At Vandenberg, the pioneers of the mission, such as Tom Schmugge, a retired NASA engineer who first came up with the idea of a soil moisture mission, and other scientists who have dedicated their lives to the mission, erupted with cheers, hugs and handshakes.

"I think everyone who contributed to this mission has to feel very relieved because the first critical steps have been taken without any glitches," said Ted Engman, a retired NASA engineer who worked on the SMAP mission for much of his career, via email from outside Vandenberg.

The satellite passed over three ground-based tracking and relay stations in Svalbard, in Alaska and at McMurdo Station in Antarctica, and communicated with all three successfully, said Kent Kellog, project manager at NASA's Jet Propulsion Laboratory.

The most nerve-racking parts were over, and the next step to watch would be the deployment of the spacecraft's giant antenna 11 days hence. Large as a Ferris wheel, this antenna contains a gold reflector mesh and is the only part of the satellite that has not been tested on Earth because of its humongous size.

The satellite will pulse at the Earth microwaves that will bounce off the moisture contained within soil. The satellite's antenna will catch the reflected waves and detect shifts in energy, which will reveal the amount of water contained in soils the world over, from the Arctic to the tropics.

SMAP is the fifth earth science mission NASA has launched in the past 11 months (ClimateWire, Jan. 15, 2014).

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500

It’s Time to Stand Up for Science

If you enjoyed this article, I’d like to ask for your support. Scientific American has served as an advocate for science and industry for 180 years, and right now may be the most critical moment in that two-century history.

I’ve been a Scientific American subscriber since I was 12 years old, and it helped shape the way I look at the world. SciAm always educates and delights me, and inspires a sense of awe for our vast, beautiful universe. I hope it does that for you, too.

If you subscribe to Scientific American, you help ensure that our coverage is centered on meaningful research and discovery; that we have the resources to report on the decisions that threaten labs across the U.S.; and that we support both budding and working scientists at a time when the value of science itself too often goes unrecognized.

In return, you get essential news, captivating podcasts, brilliant infographics, can't-miss newsletters, must-watch videos, challenging games, and the science world's best writing and reporting. You can even gift someone a subscription.

There has never been a more important time for us to stand up and show why science matters. I hope you’ll support us in that mission.

Thank you,

David M. Ewalt, Editor in Chief, Scientific American

Subscribe