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Press release
No. 395e
June 17
World’s largest mirror telescope relies on
nanometer accuracy sensors from Micro-Epsilon
The European Southern Observatory (ESO) based in Garching,
Germany, relies on high precision displacement measurement from
Micro-Epsilon for a project to build the world’s largest mirror
telescope in Chile which also involves the French cooperation partner
Fogale. The inductive sensor systems used for displacement
measurement are the most precise ever used in a telescope. They
determine the position of each single mirror segment in three axes to
nanometer accuracy.
The construction of the largest, optical and near-infrared telescope in the
world is progressing - completion is planned in 2024. The revolutionary
European Extremely Large Telescope (E-ELT) is a project of the European
Southern Observatory (ESO) on the Cerro Armazones mountain in Chile
and will be second to none in size. A major contract for this project
involving several thousand high precision sensors has now been awarded
to sensor specialist Micro-Epsilon in Germany. With more than 6,000
engineer-years of experience and 120 patents, Micro-Epsilon stands out
due to its widespread knowledge in high precision sensor technology. The
globally operating sensor manufacturer employs around 1,000 people in
the Group, with almost 400 at its Lower Bavarian headquarters.
The sensors for the giant telescope supplied by Micro-Epsilon play a
crucial role in this research project. The telescope uses a unique, optical
system with five mirrors and requires optical and mechanical elements that
push modern technology to its limits. The diameter of the main mirror alone
will be 39 meters - half the length of a soccer field. With a total surface
area of 978 square meters, the mirror consists of 798 single segments,
each 1.4 meters in size but only 5 centimeters thick. These honeycomb
segments must be aligned precisely to each other in order to form a perfect
optical system. Their relative position can change due to outside
Micro-Epsilon
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Tel.: +49/8542/168-0 ·
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interference from wind loads, fluctuating temperatures and, last but not
least, gravity which has different effects depending on the respective
alignment of the E-ELT. The sensors provided by the FAMES consortium
(Fogale and Micro-Epsilon), ensure exact positioning to nanometer
accuracies. Micro-Epsilon is responsible for manufacture of the sensors,
which are the most precise ever used in a telescope. Measuring the
relative position to nanometer accuracies therefore represents the
fundamental core of this complex system. Predestined for outdoor
applications, the sensors stand out due to their long-term temperature
stability, as well as their high resistance to external influences.
The major challenge in this large-scale project involving more than 5,000
inductive displacement measurement systems is to achieve the required
measurement precision to nanometer accuracy under such difficult ambient
conditions. Micro-Epsilon’s managing director Martin Sellen is satisfied with
the ESO cooperation: "After developing these high precision sensors for
such an important project, we can finally deliver the essential component
for the world’s largest mirror telescope. The whole construction project
pushes the boundaries of technical feasibility and so requires a longer
planning period. In addition to economic importance, we can also bring our
knowledge into international top-level research."
The sensors used are based on the principle of inductive coupling and
Micro-Epsilon’s widespread knowledge eddy current measurement
technology. The sensors measure on a wear-free, non-contact basis
providing the highest precision and resolution. A special advantage of the
sensor is its immunity to external influences such as dirt, pressure and
humidity. The sensor consists of a transmitter coil and an opposite located
arrangement of several receiver coils on the adjacent mirror segment. The
transmitter coil is supplied with alternating current. The voltage induced by
inductive coupling in the receiver coils depends on the position of the
transmitter coil. The patented evaluation of the partial signals enables the
determination of the position of the segments relative to each other in three
axes. The special coil is designed in accordance with Micro-Epsilon’s
Embedded Coil Technology (ECT) eddy current sensors, which differs
significantly from the wound coils found in conventional sensors. The coil
itself is embedded in an inorganic carrier material. Their innovative design
provides the sensors with an extremely high temperature rating and longMicro-Epsilon
Messtechnik
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Tel.: +49/8542/168-0 ·
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term stability, as well as excellent repeatability.
Building such an enormous telescope fulfils an important role in groundbased astronomy and should expand astrophysical knowledge significantly.
The next generation E-ELT telescope enables the exploration of red-shifted
galaxies, star formation, exoplanets and protoplanetary disks. With this
project, ESO wants the E-ELT telescope to revolutionize the exploration of
the universe with its gigantic main mirror and adaptive optics (AO)
technology - just as Galileo did 400 years ago, when he was the first to turn
a telescope towards the sky. The telescope may help to answer some
major scientific challenges of our time. Do other Earth-like planets exist
that we could live and survive on? What are the characteristics of the first
stars and galaxies, dark matter, dark energy and early Black Holes?
The telescopic system has a total weight of 2,800 tons and can rotate
through 360 degrees. Compared to today’s high-end telescopes, the E-ELT
telescope will be four to five times larger and receive 15 times more light. It
will capture 100 million times more light than the human eye, 8 million
times more than Galileo’s telescope, and in total, more light than all
existing 8- to 10-meter-telescopes on Earth.
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Micro-Epsilon
Messtechnik
[email protected]
Tel.: +49/8542/168-0 ·
www.micro-epsilon.com
Further information:
www.microepsilon.com/press
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