The satellite feels.

BBC News reports on a new kind of observational satellite overhead. It’s not looking down at us – it’s feeling our weight:

As Goce “bumps” through Earth’s gravity field, the accelerometers will sense fantastically small disturbances – as small as one part in 10,000,000,000,000 of the gravity experienced at the Earth’s surface.

This exquisite measurement capability meant some very fragile mechanisms had to be built into the gradiometer, and developing these delicate technologies so they could also survive the intense shaking experienced at launch proved to be one of the major design challenges of the mission.

How sensitive is that?

The buffeting from air molecules would ordinarily upset Goce’s gradiometer instrument, so the British engine is designed to throttle up and down to counteract this disturbance and leave a clean signal.

The levels and range of thrust needed, however, are tiny – a continuously variable force of anywhere between one and 20 millinewtons during the science phase of the mission.

This is similar to the force a postcard will exert when laid down on a surface.

Put another way, you would need to strap together 650 million Goce spacecraft to achieve the same amount of thrust as Europe’s mighty Ariane rocket at launch.

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