Feasibility study: done!
Tremendous gains in sensitivity and angular resolution over large fields of view at CFHT are
possible. The potential is striking and the scientific impact covers areas from the Solar System to
the most distant objects in the universe. Improving the delivered image quality of the telescope to
Mauna Kea's exquisite free-atmosphere seeing reduces confusion noise in crowded fields such as
star clusters and dense regions in the Milky Way allowing greatly improved photometry and
astrometry and increases the sensitivity depths to a level where CFHT will play an important role in
z>7 galaxy searches, high redshift supernova cosmology, weak lensing and galaxy and stellar
evolution. CFHT is effectively upgraded to an 8-10-meter class telescope.
This report represents the culmination of the IMAKA feasibility study. We conclude that median
angular resolutions of 0.3" in the visible across a one-degree field of view are within reach of
CFHT. Our main conclusions of the study are as follows:
Previous studies on the local turbulence above Mauna Kea and within the CFHT enclosure
are confirmed with our new measurements: the local seeing is comparable to the
atmosphere. We infer that this local seeing is inside or just outside the CFHT enclosure.
We find that an approach using a ground-layer adaptive optics system plus a focal plane
detector based on orthogonal-transfer CCDs will deliver superb resolutions under median
seeing conditions. The cumulative probability of obtaining a particular level of performance
(or better) from the GLAO+OTCCD correction shows significant improvements in the
image quality under all seeing conditions. Under median conditions, the telescope will have
the sensitivity of an 10-m telescope and deliver angular resolutions unmatched over a onedegree
field of view.
We have two optical designs (one at prime and one at Cassegrain focus) that meet the basic
functional and performance requirements. Both designs use a deformable mirror that is
commercially available. Neither design uses an adaptive secondary. We believe that both
The cumulative probability distribution of `IMAKA image quality (GLAO+OTCCD) for the input seeing
conditions considered within the study. We predict that half of the time `IMAKA can deliver
better than 0.37" in
g' (0.5um), 0.31 in r' (0.7um), 0.26" in z' (0.9um), and 0.25" in Y band (1um).
designs can be realized and that there are no fundamental or technical "show-stoppers" for
`IMAKA.
The scientific drivers for `IMAKA are the combination of wide field and high angular
resolution. There are no current or planned ground-based facilities with similar capabilities.
In addition, `IMAKA on CFHT will present a complementary capability to future/planned
space-based missions. A timely delivery though is needed to maximize the scientific impact
of the system.
The breadth of the science cases reflects the broad interest within the community and their
desire for wide-fields and high angular resolutions. The cases cover the full spectrum of
astronomical objects and studies and the instrument is a natural extension of the expertise
and science developed over two decades of wide-field visible imagers at CFHT.
To be most effective, 'IMAKA should come online at roughly the same time as JWST (2015) (and
presumably when HST is no longer available) and before potential space missions such as JDEM
and EUCLID. This will require timely decisions.
A Phase A study will provide the needed level of study to make informed cost/schedule
decisions on the future of the instrument.
A delay now will impact the delivery of the instrument and dilute the full scientific impact
from `IMAKA.
We believe that the instrument can be built and that it can be built within an overall 5-year
development plan. To meet this schedule will require an increased level of resources and a firm
commitment from the observatory and the community.
Want to know more about `IMAKA?
Instrument ConceptThe whole public feasibility report
