Scientific News

'Sugar-cube' sensors to monitor Earth's orientation

One of ESA's future Earth observation missions will monitor Earth's orientation in space with the help of the smallest gyro ever flown by Europe.

Figure 1.
MEMS gyros will fly on ESA's
Sentinel-3 satellite, scheduled to
be launched in 2013, which will
provide global ocean, ice and
land vegetation observations
Image courtesy of ESA / J Huart
Click on the picture for a larger
version

May 2010 - Now being tested, the sugar cube-sized device at the heart of the gyro unit is derived from a sensor used in anti-lock braking systems on millions of cars: micro-electro mechanical systems (MEMS).

There is no up or down in space. Satellites track their pointing direction using the same approach that is used onboard submarines and aircraft: fast-spinning gyroscopes that maintain a fixed orientation in the same way as a child's spinning top. But space-quality gyros employing this principle are complex, bulky and insufficiently reliable for long space missions.

For ESA, therefore, MEMS are an especially promising innovation. They are made in a similar way to microprocessors but incorporate moving parts or sensors, enabling complete devices to be fitted onto a single silicon chip.

Figure 2.
Click on the picture for a larger
version

Attractive for space because of their small size, low power consumption and resistance to vibration, these micro-machined devices may sound exotic, but MEMS sensors are already used in their millions on European roads. In the last 15 years, the automobile industry has adopted MEMS in a major way. The devices are embedded throughout modern cars: MEMS accelerometers trigger airbags, MEMS pressure sensors check tyres and MEMS gyros help to prevent brakes locking and maintain traction during skids. And soon there will be MEMS in space, helping to monitor the orientation of Earth. Not bad for something the size of a sugar cube.

To find out more about the use of MEMS in Earth observation, visit the ESA website.