Optical interferometry in Antarctica : a future for European astronomy ?

1
Optical interferometry in Antarctica a future
for European astronomy ?

• Pierre Léna
• Université Paris Diderot (emeritus)
  Observatoire de Paris
• Final plenary conference of the ARENA network
• Frascati, May 11-15 2008

2
How did the VLTI begin (1980-1990) ?

• Optical interferometers in their infancy (1975 !)
  
• Although promising, little science done,
• Behaviour of atmosphere vs.wavelength (-gt IR)
• Seeing conditions totally critical
• But maturity of radio-interferometry
• No large pupils (providing sensitivity) without
  AO
• Emergence of adaptive optics in early 1990s

3
Taking the risk of VLTI ?decision 1987

• Scientific potential, essentially for Galactic
  sources
• Demonstration of AO practical use
• Reasonable cost-to-benefit ratio of investments
• Full inclusion of VLTI in the global VLT program
  (4UTs 2ATs)
• Balance between skepticism and determination
• Progressivity and phasing in the construction
  progress
• Evidence, although limited, of C. Paranals
  superiority
• A major blow (VISIR) avoided in 1986
• Then additional contributors (D, F, ND, B) adding
  resources (1987-1997)

4
The VLTI concept, as it appears in the VLT
approval document (1986-1987)
5
The situation in 2009

• Optical interferometry assessement cf. Ridgway
  Glindemann (2009)
• Positive aspects
• Remaining issue on sensitivity throughput (AO
  related) and seeing (site related)
• Space interferometry still is in a remote future
  
• Exceptional flexibility of VLTI 4 UTs 4 (5 ?
  6?) ATs
• Several scientific modes astrometry, imaging,
  spectro-imaging
• Second generation instruments e.g. GRAVITY
• Excellent  competitors/complementary  CHARA,
  LBT, MROI, OHANA
• Long term future 2020 or more

6
Which strategy for the post-VLTI era ?In the
light of the 1980 era

• Either to wait until present issues are fully
  solved ?
• Or
• To acknowledge for unknowns
• To trust in a progressive emergence of solutions
  
• To consider optical interferometry has a
  long-term scientific future
• To accept that this future is ground -based for
  possibly 2 decades
• 1. Expansion from present hectometric to
  kilometric arrays agreed
• 2. Issue of telescope size (sensitivity),
  mobility and number (imaging) is open
• 3. Quality of the site is absolutely critical
  seeing, transparency

7
ESO and interferometry in the long term ?In the
light of the 1980 era

• Could the community proceed without ESO ?
• ESO is busy with ALMA and E-ELT for more than a
  decade
• No real legitimity and European federative action
  in interferometry without ESO
• Recognizing a general responsibility of ESO for
  the post-VLTI era, but
• Finding a limited but adequate role for ESO in
  the immediate future.

8
Interferometry in Antarctica

• An exceptional site in terms of seeing and
  transparency ?
• Difficult logistics, but with what does one
  compare it ?
• A new place, between classical ground-based
  observatories and space-based ones
• The site value of Antarctica needs to be fully
  clarified in the next decade
• ESO has all the needed compentencies to do it at
  the right scale in the right time
• Many European collaborations available towards
  this goal
• Demonstrative interferometry project(s) to be
  done in 2010-2020
• Alladin seems the right goal, size and cost
• Kheops has to wait, but is a good candidate for
  the post-VLTI strategy
• Funding impossible through ESO, competes with
  E-ELT fund search

9
Antarctica is a model continent for globalisation

• Making Antarctica a broader and global issue for
  Europe
• European Research Council
• European Union Commission
• European Science Foundation
• Exploring in depth EU collaboration with China (
  others)