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Interferometry IR and optical

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#1 dickbill

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Posted 29 December 2011 - 11:25 AM

I find this topic fascinating, especially since we have hundreds of identified star systems. Earth based interferometers are better than nothing but only in space can they reach their peak performances. Since there is no TPF project, i would kind of hope for a modest project on the ISS...
Anyway, I'd think a topic that shows the progress and results in the matter would be interesting.

So here the link of Labeyrie's publications, a french pionneer in interferometry
http://www.oamp.fr/l...blications.html

In the following article you'll find a real picture of Castor and Pollux
http://www.oamp.fr/l...is/gilletAA.pdf
It's earth based with very modest telescopes. Apparently optical interferometers don't go very deep in magnitude.

Here is another article from Riaud et al.
http://www.aanda.org......396..345RFUL
It was part of a proposal for the TPF. The introduction states that:" Searching for Earth-like planets is the challenging goal of NASA's Terrestrial Planet Finder (TPF hereafter) space mission. The original instrument concept is based upon the idea of a nulling interferometer, according to Bracewell's option (Bracewell 1978; Bracewell & McPhie 1979) of using a beam-splitter to produce a destructive interference in the star's wavefront received from a pair of apertures. Recent theoretical work in interferometry (Labeyrie 1996) provided us with a new concept for the instrument, the hypertelescope, for which numerical simulations and signal/noise ratio calculations have been presented in Boccaletti et al. (2000). These calculations have shown that such multi-aperture snapshot imaging interferometers outperform the former nulling interferometer concept for the search for exo-planets..."

in the paper, there is a simulation of the Solar System seen from 20 parsec with a 80 meter baseline 37-elements hypertelescope, which shows Venus and Earth. This size, i believe, could easily fit on the ISS, although maybe not with so many telescopes.

Here's the site for the VLT-I (VLT-interferometer)
http://www.eso.org/s...s/vltiws05/#EII

Web site for the European Interferpemtry Initiative
http://www.european-...rometry.eu/home
Which point to NASA http://olbin.jpl.nas...otos/index.html
unfortunatly with many dead links.

Look at the spectacular pictures from the IOTA project (now closed, that's a reward!):
http://tdc-www.harvard.edu/IOTA/
Variable Chi Cygni in IR, real picture! and partially cg movie:
http://www.cfa.harva...923_images.html

#2 dickbill

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Posted 29 December 2011 - 11:53 AM

This slide presentation, from Labeyrie again, contains a simulation of Earth seen from 10 lightyears by a flotilla of 150 3-meters mirrors spread over 100 km in space at L2.
http://www.oamp.fr/l...STEC2009Max.pdf

It looks like a very advanced and ambitious project, but probably much less expensive than the ISS project. And there are certainly many modest projects that are doable right now within the ~hundred meter baseline. A redesigned version of the TPF much smaller than that (like <30 meters) would seem too redundant with the terrestrial baselines capabilities, so the future TPF has to be >80 meters to be really interesting (but still fit the ISS), that's my guess.

#3 dickbill

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Posted 03 January 2012 - 01:41 PM

This is considered the first image of an exoplanet, according to the Keck observatory.
http://keckobservato...ery/detail/106/
http://keckobservato...lery/detail/98/

Unfortunatly there is no technical informations beside using adaptive optics in the IR for the second image, so without using interferometry.

#4 Charlie B

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Posted 03 January 2012 - 05:39 PM

You may want to look here.

Charlie

#5 dickbill

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Posted 04 January 2012 - 09:48 AM

Thanks for the link Charlie. Here again the authors affirm that it is the first real picture of exoplanets, taken in 2007 and 2008. And that's only using adaptive and substracting techniques to 'match or surpass' Hubble resolution capabilities.

With all the ground-based baselines for interferometry in the range 80 to ~few hundred meters it appears there is no need for a similar baseline in space, but i still think a ~100 meter sized demo version in space (or based on the ISS structure) would achieve more and faster than the earth-based interferometers.
I've look on the ESO VLT-i and Keck web sites for interferometry images, and there is only a trickle of results, with 2-3 years old promisses of more results coming soon....
It seems that IR and optical interferometry on the ground are plagued with many problems like seeing and ground movements that take all the energy of the engineers. Obviously in space the seeing is gone, that's a big one and, assuming the ISS were used to support a baseline, the only problems would be vibrations and temperature variations. Work from Labeyrie's team indicate that more smaller telescopes is better than fewer big one, and that's really a good thing because of the mirrors mass. A single launch to the ISS could deliver dozens or 30 cm mirrors. It's really weird that nobody suggested such a test bed on the ISS.

#6 dickbill

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Posted 28 November 2012 - 02:35 PM

Pluton and Charon at 20 milliarsec resolution
http://www.gemini.edu/node/11893

Impressed, or not yet?






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