In the Naini Valley between the slopes of the Himalaya
Mountains, the incredibly clear sky reflects off of the droplet-
shaped lake. Hindu mythology says that “Nain”, the eye of the
divine Sati, fell down to the ground here. Nevertheless, it isn’t
mythology that the Aryabhatta Research Institute of
Observational Sciences (ARIES) focuses on here, but rather
what is happening outside our world.
“We are planning to build India’s largest optical astronomy
telescope in the nearby Devasthal”, says Professor Ram
Sagar, Director of ARIES. “It is scheduled to go into operation
in 2012 and has been optimized for the spectroscopic
exploration of the Milky Way. By observing the color spectrum
of the light sources, one can determine physicochemical
processes, as well as the internal structure or the temperature
of the celestial bodies”, Prof. Sagar explains.
Eye made of glass ceramic
The telescope is equipped with a 3.7 meter mirror made of
“Zerodur” from SCHOTT. “Zerodur” is a glass ceramic that is
particularly known for its coefficient of thermal expansion that is
close to zero. This prevents deviations from occurring while measuring the sky, as a result of shifts in temperature.
Additionally, this material features extremely high homogeneity,
chemical stability and excellent long-term stability of the
mechanical properties. For this reason, “Zerodur” from
SCHOTT is the mirror substrate material that is used in most of
the world’s large telescopes.
“The high quality of the mirror material is of immense
importance for a telescope of this size,” explains Frédéric
Rausin, project manager at AMOS S.A. Advanced Mechanical
and Optical Systems in Liège (Belgium). “Besides, the fact that
SCHOTT has so many years of experience with major
astronomy projects was of great benefit. This made it possible
to complete the extensive processing of the mirror substrate for
the active optics of the mirror that significantly improves the
image sharpness of the telescope in a very short time,” he
adds.
Distortion-free view of the stars
“In order to be able to take on the 69 actuators – machines
similar to a “mechanical” muscle – of the active optics, pockets
with extremely narrow tolerances were integrated into the back
side of the mirror substrate,” explains Dr. Thorsten Döhring, an
expert on astronomy projects at SCHOTT Advanced Optics in
Mainz (Germany). “Now, the mirror can be adjusted in the
nanometer region at these points. This allows for the bending
of the mirror that is caused by gravity to be compensated for
while tracking the telescope,” Döhring adds.
SCHOTT received the order to provide and process the
“Zerodur” substrate from AMOS, the general contractor, in
September of 2008. Only a few months later, in March of 2009,
the glass ceramic monolith was delivered to the polisher as a
heavy load. Once it has been completed, the eye on the sky
will be sent to Liège (Belgium), where the specialist for opto-
mechanical systems AMOS will complete assembly and
perform extensive tests. As soon as these have been
concluded, the entire system – 13 meters high and around 120
tons in weight – will be dismantled into modules of 15 tons each. Then, they will begin their long voyage to the Himalayas
by heavy transport in order to be able to follow Sati’s view of
the sky starting in 2012.
SCHOTT is an international technology group that sees its core
purpose as the lasting improvement of living and working conditions.
To this end, the company has been developing special materials,
components and systems for 125 years. The main areas of focus are
the household appliances industry, pharmaceuticals, solar energy,
electronics, optics and the automotive industry. The SCHOTT Group
is present in close proximity to its customers with production and
sales companies in all its major markets. The Group’s approximately
17,300 employees generated worldwide sales of approximately 2.2
billion Euros in the fiscal year 2007/2008. The company's
technological and economic expertise is closely linked with its social
and ecological responsibility. The SCHOTT AG is an affiliate of the
Carl-Zeiss-Stiftung (Foundation).
AMOS is specialized in design and manufacturing of high accuracy
optical and mechanical systems. For the space industry, AMOS is
producing equipment to test satellites and payloads on ground as well
as mirrors and mounts to fly on board spacecraft. AMOS is also
delivering tailor-made equipment to professional astronomy from focal
plane instruments to complete large size telescopes.
Further information: www.amos.be
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