No country wants to discover it is facing a food shortage, but too often countries find out about shortages after they are too late.

Faced with this conundrum, NASA wants to help developing countries bedeviled by food security. Satellites can't make it rain, but they can predict a bad crop season before it happens.

NASA launched the Aqua mission back in 2002 to monitor the world's water cycle from space. At the conference for the American Geophysical Union last week, NASA's John Bolten unveiled a plan to use Aqua to check the moisture content of soils in West Africa and predict what the crop yields might be under varying conditions.

You need two kinds of water information to accurately predict crop yields-how much is in the ground already and how much is going to fall from the sky. Weather prediction can only be so reliable over the course of a season, so Bolten focused on refining the subterranean measurements.

Unfortunately, ground-level sensors that measure soil moisture can be scattered hundreds of miles apart in West Africa, separated by varied terrain. To get around this problem, he wants to make the measurements from space.

The Aqua satellite will measure radiation in the microwave spectrum that emanates from African soil. The amount of microwave radiation the land gives off is related to the water content in the soil, and by making these measurements from space, NASA could create a map of soil moisture that covers an entire region but is detailed down to local areas. If the map tells us that the land is dry and crop yields will be low this year, governments and aid agencies can prepare in advance to meet the food shortage.

Bravo, NASA. If soil moisture monitoring from above works, it could be one of those simple-but-smart ideas, like Amy Smith's low-tech solutions and Dean Kamen's water purifier, that developing countries need.