European Solar Telescope (
Author profile picture

When astronomers use telescopes to monitor and take images of space objects, the earth’s atmosphere can distort the image – much like the weather can cloud the lens on a camera. Telescopes that orbit in space, such as the Hubble Telescope, do not have this issue since they avoid the atmosphere altogether. However, the most powerful telescopes are also the largest and, for now, these are built on earth.

To correct for the optical distortions caused by the atmosphere, Adaptive Secondary Mirrors (ASMs) can be built in to earth-bound telescopes which allow for a clearer image of space. A bid by TNO has been selected for the preliminary design one such ASM for the European Solar Telescope (EST), so it can be used to better monitor the sun’s activity.

Balanced actuators

The ASMs are mirrors that change shape in order to correct for the issues our atmosphere creates. To achieve this, the adaptive mirrors are mounted on actuators – devices that push and pull the mirrors in a way that change their shape (or optical prescription). Much of the innovation that TNO submitted, and ultimately won the bid for, is built around these actuators as they are more reliable and efficient than the competition.

“The key to our technology is that we have reinvented the deformable mirror actuator,” says Matthew Maniscalco, one of TNO’s team members involved in the project.

Other actuator designs rely on floating electro-magnets to move the mirrors, meaning that the force can change depending on the distance from the magnet. TNO’s actuator design is physically attached to the mirror and is engineered with a spring, electromagnetic coils, and fixed magnets that keep the forces balanced and linear. This means it can be more energy efficient and precise.

Impression of the EST-ASM, courtesy of TNO

Studying the sun and space

The success of this design will allow the EST to monitor the sun and even predict for disturbances like solar flares. The radiation that comes from solar flares can be very harmful to satellites – but by simply turning the sensitive satellites systems off, one can protect against much of the damage. Thus, being able to predict for solar flares can be very useful for satellite longevity.

Larger telescopes are being built all over the world to understand phenomena like this but Maniscalco hopes that the technology can be used to keep existing telescopes relevant.  

“We believe our technology can be used to retrofit really great, older telescopes to help them compete with upcoming new giant telescopes,” says Maniscalco.

Read about how citizens can help look for black holes with the LOFAR telescope.