ESA's Darwin mission aims to discover extrasolar planets and examine their atmospheres for signs of life, particularly for the presence of certain life-related chemicals such as oxygen and carbon dioxide. The major technical challenge lies in distinguishing, or resolving, the light from an extrasolar planet from the hugely overwhelming radiation emitted by the planet's nearby star.
The multi-satellite Darwin mission will use optical interferometry in which at least three separate orbiting telescopes jointly operate as an equivalent single telescope with a much larger effective aperture, thus achieving the required resolution. With this method, multiple smaller telescopes having actual apertures of, for example, 3 metres, can combine to provide an effective aperture of several tens to hundreds of metres, depending on the distance between the individual telescopes.
Creating delicate phase delays
Darwin will use nulling interferometry, a specific interferometric technique used to shield the overwhelming star emissions by precisely delaying the radiation coming from some of the telescopes by a small amount. This, in combination with achromatic - or colour independent - phase shifters, will cancel out the bright star radiation while allowing the much fainter extrasolar planet light to be detected.
A component known as an Optical Delay Line (ODL) is at the core of such interferometric observations. An ODL is a sophisticated opto-mechanical device that can introduce well-defined variations, or delays, in the optical path of a light beam and includes a moving mirror positioned with extremely good accuracy.
Precise movement using magnetic levitation
To demonstrate the critical technology required by Darwin, ESA's Technology Research Programme has sponsored the design and testing of an ODL that uses magnetic levitation for precise, frictionless mirror movement. The ODL's wonderfully sophisticated guidance and translation mechanism is, thanks to the magnetic levitation, completely contactless and frictionless and can be easily displaced by the faint touch of a feather (see video clip accompanying article).
The optical delay introduced by the ODL must be capable of adjusting the optical path length of collected light beams with an accuracy of a few nanometers; 1 nanometre corresponds to a millionth of a millimetre.
Under ESA sponsorship, the ODL was built by an industrial consortium led by TNO Science and Industry, part of The Netherlands' Organisation for Applied Scientific Research, and including SRON and Dutch Space in the Netherlands, Belgium's Micromega-Dynamics s.a. and the Centre Spatial de Liège, and France's Alcatel Alenia Space and Sageis CSO. The ODL magnetic suspension technology was pre-developed by Micromega-Dynamics under the ESA-funded MABE (Magnetic Bearing) research study, which included quasi-zero gravity testing during parabolic flights.
Sub-nanometre resolution to be incorporated in future flight mechanism
The ODL shown here successfully demonstrated sub-nanometre resolution and stability; the design, materials and manufacturing processes for this ODL are representative of a future flight-capable mechanism.
The ODL has also been thoroughly tested in Darwin's demanding cryogenic environment, at 40 Kelvin - or about -233 Celsius.
Darwin's ODLs are uniquely engineered to operate at cryogenic temperatures to avoid self-interference from the satellites' own thermal radiation. This is mandatory as Darwin will conduct observations at mid-infrared wavelengths, where the planet-to-starlight brightness ratio is relaxed compared to that in visible wavelengths, and where life-related marker chemicals such as water, ozone and carbon dioxide can be detected.
The ODLs will be used in Darwin for co-phasing the light collected by the separate telescopes within a central hub spacecraft, which is responsible for the correct recombination of the light beams and hence achieving the high-performance resolution of a single very large telescope.
Malcom Fridlund | alfa
From rocks in Colorado, evidence of a 'chaotic solar system'
23.02.2017 | University of Wisconsin-Madison
Prediction: More gas-giants will be found orbiting Sun-like stars
22.02.2017 | Carnegie Institution for Science
In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport
Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...
The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.
The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...
Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...
Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".
Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...
13.02.2017 | Event News
10.02.2017 | Event News
09.02.2017 | Event News
24.02.2017 | Life Sciences
24.02.2017 | Life Sciences
24.02.2017 | Trade Fair News