Grace Maps the Earth's Gravitational Field

The US-German Gravity Recovery and Climate Experiment mission (aka Grace) has taken the last two weeks to produce the most detailed map of the Earth's gravitational field - lumps and all. Launched in March, the twin spacecraft have been orbiting the planet 16 times a day, 220 km apart from one another. A ground-based microwave ranging system measures the distance between them to see how they speed up and slow down due to changes in gravity. And this is just the low res version; scientists hope to have even more detailed maps by the end of the year.