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Surrey Satellite Technology (SSTL) has utilised a three-component dynamometer manufactured by Kistler Instruments to simulate the operation of the positioning wheels on one of its satellites.

Today’s SSTL satellites have evolved from earlier designs using the best available technology to minimise cost and maximise reliability.

The launch phase places huge vibrational loads on the payload making the need to over engineer and thoroughly test every component essential to ensure that these loads do not compromise the performance of the satellite.

Typically, the positioning wheels – a type of gyro that maintains the satellite in alignment with a ground station antenna when downloading data or a specific area when imaging – use precision ball race bearings that can become pitted in the launch phase, resulting in electro-mechanical noise during in-space operation.

This noise can interfere with the operation of the delicate electronics used for imaging and navigation systems on the satellite.

To simulate the operation of the positioning wheels, SSTL use a test rig based on a three-component dynamometer from Kistler Instruments, which measures the forces produced by the positioning wheels.

It is this force that, in space, maintains the satellite antenna in line with an earth station or a particular constellation depending on the mission objective.

When the positioning wheels run at around 5,000rpm to make a large change in the satellite position, noise is not a problem, but when making small, repeated adjustments, noise can cause camera shake resulting in blurred imaging or loss of lock in the star camera positioning system.

‘We chose the Kistler dynamometer and amplifier combination as we needed the long-term stability and precision provided by the piezoelectric force sensors used in the instrument,’ says SSTL’s Andrew Haslehurst.

Kistler Instruments

Established in Winterthur (Switzerland) in 1957, the Kistler Group now has a worldwide presence with 23 group companies and 30 distributors ensuring prompt, local application support and short delivery times. With a staff of more than 1,000, the Kistler Group is one of the world’s leading providers of dynamic measuring instrumentation.

Kistler’s core competence is the development, production and use of sensors for measuring pressure, force and acceleration.  Kistler’s know-how and electronic systems can be used to prepare measuring signals for use in analyzing physical processes, controlling and optimizing industrial processes, improving product quality in manufacturing and improving performance in sports and rehabilitation.

Kistler offers a comprehensive range of sensors and systems for engine development, automotive engineering, plastics and metal processing, installation technology and biomechanics.

Heavy investment in research and development, 15% of staff worldwide are engaged in research and development, has generated a number of innovations using piezoelectric, piezoresistive and capacitive techniques to provide solutions to numerous force, pressure and acceleration measuring problems. These innovations include the world’s first commercial quartz sensor, two-wire constant current technology to integrate sensors with microelectronic circuitry, high-temperature pressure sensors for use up to 400 Deg C and three-component force measuring sensors.

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