Led by professor Darwin Caldwell, the international team created HyQ with a special Inertial Measurement Unit (IMU).

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The decision to bring the shuttle down came after one of the orbiter's three key navigation tools -- an inertial measurement unit -- stopped working.

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The calculation is rough and ready, and I come to slightly lower numbers than Allwood and co, but the point is that this measurement uses a unit we're familiar with - us.

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Other likely candidates for stock tickers: Zipcar (a car rental service), Nielsen (media measurement firm) and NXP Semiconductors, a unit of Royal Philips Electronics.

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