SMAP: Gotta Like It!

SMAP didn’t launch last Thursday morning when we both were there to see it in person. Nor did it launch the next morning, even though Anna had stayed in hopes of seeing the launch. It launched on Saturday, January 31. See our preview SMAP post LAST WEEK.

We’re not too upset that we missed the launch. That’s the way it is with rockets and us. And we can’t help liking SMAP—JPL’s Soil Moisture Active Passive satellite. Here are five reasons why.

It looks great.

SMAP Model
SMAP Model

The 19-foot mesh antenna is an unfolding feat of engineering, somewhat like origami done backwards. After about three weeks in orbit to make sure all is well for SMAP, a wire snips, and the stored energy of the scrunched-up mesh allows the antenna to bloom like a flower. Once fully deployed, the antenna rotates, a bit like a lasso spinning once every four seconds above the moisture-mapping equipment. In simulations that NASA showed, it looks as if SMAP is waltzing through its orbit.

California, where we live, is in the midst of a drought.

We know you’ve heard the news about California’s drought, which is getting to be old news. NASA’s Randy Koster, from Goddard Space Flight Research Center, suggested that an end in sight any time soon for California’s drought would be akin to a miracle. SMAP can’t end a drought, but data from SMAP will help us learn how to predict droughts and the end of droughts in the future.

Soil moisture, he said, has an inherent memory. This status quo means that wetter soil tends to stay wetter the next day, and drier soil tends to stay pretty dry. Higher evaporation from wetter soil leads to greater chance of rain. SMAP’s information about soil moisture, based on measurement of the whole globe’s soil every two or three days, will help us understand this cycle and predict trends for each particular geographical area

The daily and weekly information we get about soil moisture and use all the time is based mostly on computer simulations, not on regular, comprehensive measurements.

SMAP visualization (NASA)
SMAP visualization (NASA)

Together, NOAA (National Oceanic and Atmospheric Administration) and the National Weather Service report soil moisture and use it, along with other data, to make predictions. These reports go out to weather forecasters all over the United States, and they make local predictions based on these reports. Farmers use this information, too, for instance, when planning when to plant crops. One reason that we need accurate, up-to-date soil moisture information is because, in areas where soil is more saturated, flooding can occur more quickly. Soil moisture reports are especially important when trying to predict flash floods.

These crucial reports are based on relatively few actual measurements by real sensors in the ground, which computers use to produce models for larger areas. If I measure the moisture of the soil in my yard, am I able to predict what’s going on to the west nearer the ocean or to the east nearer the mountains? In other words, there aren’t enough sensors in the ground measuring soil moisture, and outside the United States, the measurements are even fewer and farther between.

SMAP changes all this. It measures soil moisture everywhere. It measures the moisture in the soil of every given place every two or three days. For the first time, flood predictions will be based on accurate, place-specific, up-to-date information.

Ice matters.

As SMAP looks at the land masses, it will be able to tell where it’s frozen. Science Daily tells why that’s important:

In summer, plants in Earth’s northern boreal regions—the forests found in Earth’s high northern latitudes—take in carbon dioxide from the air and use it to grow, but lay dormant during the winter freeze period. All other factors being equal, the longer the growing season, the more carbon plants take in and the more effective forests are in removing carbon dioxide from the air. Since the start of the growing season is marked by the thawing and refreezing of water in soils, mapping the freeze/thaw state of soils with SMAP will help scientists more accurately account for how much carbon plants are removing from the atmosphere each year.

It’s predictable.

SMAP is in a Sun-synchronous polar orbit. It had to launch at about 6:20 a.m. so that it would measure soil moisture at about 6 a.m. every day, when those who plan to use the data thought it would be best. No matter where SMAP is as it circles north to south and south to north, the time on Earth under the satellite is about 6 a.m.

PeaSoupOh, and we had pea soup!

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