OHANA: Turning the Mauna Kea telescopes into a giant interferometer

Olivier Lai (on behalf of the `Ohana Committee)
Canada-France-Hawaii Telescope


"Ohana" means family in the hawaiian language. OHANA is also an acronym
for a project that aims at linking the Mauna Kea observatories into a
giant optical/infrared interferometer - the Optical Hawaiian Array for
Nanoradian Astronomy. 

Two technological breakthroughs have made such a concept feasible: 
- Large telescopes can now be equipped with adaptive optics,
  providing Strehl ratios at least 0.3 at 2 microns on faint sources
  (R<14~15). 
- Coherent light transport and coupling with single mode fibers in K
  and L bands is routinely demonstrated with the IOTA/FLUOR
  interferometer, leading to scientific results with unprecedented
  quality of visibilities (0.3% stability)

The Mauna Kea site with its telescopes, as it is right now, has a unique
interferometric potential, that is only achievable with optical fibers,
due in parts to guidelines imposed by the Mauna Kea Master Plan, but
also due to specific advantages of optical fibers. Although `Ohana
relies on advanced technology, it is all within grasp and well
understood. Some of the major challenges may actually lie in getting six
different observatories to work together towards a single goal.  The
stakes are so high, though (nothing less than the largest optical
interferometer, that will be without competition for at least another
decade) that amazing progress is also taking place on that aspect.

Finally, what astronomy can be done with hectometric baselines?
Scientific collaborations are starting and sample programs spanning from
stellar to extragalctic astronomy will be reviewed. The long baselines
and the large apertures extend the scientific capability of existing
ground interferometers (VLTI, KI), while even the demonstrator phases of
OHANA will allow to produce some unique science.