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Orbital optical interferometry?



 
 
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  #1  
Old May 25th 15, 02:42 AM posted to sci.astro.research
stargene
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Posts: 43
Default Orbital optical interferometry?

Many years ago, I would read pieces in both professional and popular
science journals that predicted that we would eventually have two or more
optical telescopes in orbit (presumably in Lagrange points?). Though
these telescopes would be separated by great distances (at the very least
by kilometers, if not tens or hundreds of kilometers), they would be some-
how slaved together and their optical signals combined as a huge optical
interferometer. The core idea was that their baseline (the great separation)
would give them a stupendous and unheard of resolution of distant
objects. Some astronomers said they could even resolve the spectra of
very complex biological molecules in the atmospheres of earth-like
planets... definitive molecules like chlorophyll. I assume that other equally
extraordinary results would be possible.

But I never see such think pieces anymore. I understand that there has
been massive defunding going on all across most pure science. Very sad
and infuriating. But is there more to it than this? Has optical
interferometry itself proved to be too intractable?
Cheers.


[[Mod. note -- Yes, this sort of optical interferometry is very hard,
i.e., requires a lot of engineering development & hence costs a lot.
A somewhat-less-hard step would be optical interferometry within a
single spacecraft, and even this has proven hard (expensive) to develop.
See
http://en.wikipedia.org/wiki/Space_I...ometry_Mission
for a space mission of this sort which was proposed in the US, and
eventually cancelled (essentially due to lack of funding).

However, in a different arena, constellations of free-flying spacecraft
with laser links have been proposed for gravitational-wave detection.
LISA,
http://en.wikipedia.org/wiki/Laser_I..._Space_Antenna
was and is the "classic" proposal of this sort. It was to have been
a joint ESA/NASA mission. NASA pulled out of the project in 2011 due
to funding limitationsr.

ESA continues to explore/plan for a scaled-down version of LISA, now
known as eLISA or NGO (most researchers strongly prefer the former
name!). Under current plans eLISA will launch around 2034. If ESA is
able to obtain funding or hardware contributions from other countries
such as China or the USA, eLISA may grow back into something close to
the original LISA proposal, and/or launch sooner.

A technology development mission to test LISA/eLISA technology,
"LISA Pathfinder", should launch this coming fall (2015).
-- jt]]
  #2  
Old May 25th 15, 02:42 PM posted to sci.astro.research
Martin Hardcastle
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Posts: 63
Default Orbital optical interferometry?

In article ,
stargene wrote:
But I never see such think pieces anymore. I understand that there has
been massive defunding going on all across most pure science. Very sad
and infuriating. But is there more to it than this? Has optical
interferometry itself proved to be too intractable?


Ground-based optical interferometry is alive and well, of course, e.g.
https://www.eso.org/sci/facilities/p...opes/vlti.html but
the requirement to compensate for the atmosphere restricts it to
comparatively bright sources and in general there are not enough
baselines to make images (models are fitted to the interferometric
data instead). Going to space would help with the first of these
problems but make the second harder.

Martin
--
Martin Hardcastle
School of Physics, Astronomy and Mathematics, University of Hertfordshire, UK
Please replace the xxx.xxx.xxx in the header with herts.ac.uk to mail me
  #3  
Old June 9th 15, 09:53 AM posted to sci.astro.research
Steve Willner
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Posts: 1,172
Default Orbital optical interferometry?

In article ,
stargene writes:
Many years ago, ... we would eventually have two or more
optical telescopes in orbit (presumably in Lagrange points?). Though
these telescopes would be separated by great distances (at the very least
by kilometers, if not tens or hundreds of kilometers), they would be some-
how slaved together and their optical signals combined as a huge optical
interferometer.


As Jonathan wrote, this turns out to be difficult and expensive,
though not necessarily impossible. A further disadvantage is that it
doesn't generate an image unless there are many telescopes.

Nevertheless, direct imaging of extrasolar planets (and zodiacal
dust) remains a high priority. Two approaches under active study are
a coronagraph and a starshade. Recent reports on both are at
http://exep.jpl.nasa.gov/newsletters.../probereports/

--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
 




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