Inside view of MEMS rate sensor

The MEMS Rate Sensor is the smallest navigation gyro ever flown by ESA, derived from automobile electronic stability control systems. It is a guest payload aboard ESA’s CryoSat-2 ice mission, launched in April 2010.

MEMS Rate Sensor on CryoSat-2

The sensor is Europe’s first Micro-Electro-Mechanical-System (MEMS) device designed for space navigation. MEMS items are manufactured in a similar manner to microprocessors but incorporate moving parts or sensors to form complete working devices. In everyday life MEMS technology is already a multi-billion euro industry – found in everything from car tyres and brakes to mobile phone cameras and inket printers.

ESA saw the potential of MEMS as a means of reducing spacecraft systems volume and mass while maintaining or increasing overall functionality. But the technology needed flight heritage to be accepted by the wider space industry.

Instead of a bulky spinning gyroscope, the MEMS Rate Sensor is based around a silicon ring on a 1-cm-square chip, kept oscillating by electrostatic forces. A trio of devices are integrated inside the flight unit to measure each axis of motion, tracking a spacecraft’s position in space.

The complete unit weighs only 750 grams – about a thousandth of CryoSat-2’s overall mass – so the mission team managed to find room for this flight experiment. The accuracy of CryoSat-2’s ice thickness measurements depend on knowing its orbital position very precisely, so the performance of the MEMS Rate Sensor results can be compared to the satellite’s own guidance and navigation control data.

An improved version of the MEMS Rate Sensor experiment is now being marketed commercially under the name SIREUS and will be used operationally for the first time on ESA’s Sentinel-3 in 2013. The sensor was developed through ESA’s Basic Technology Research Programme and General Support Technology Programme with three UK-based industrial partners: Selex Galileo, Atlantic Inertial Systems Ltd and SEA.