ESO Annual Report 2004

ased on the conservative assumption
that segments would receive unprotected
Aluminium coatings, requires that 5 segments
be processed within a single day
(10 hours, daytime). Spare segments allow
for such operations to be executed without
overhead on science time. The highest
technology involved is in the 2-m class
coating tanks, and in the metrology system
embedded into the handling tool, for
semi-automatic replacement and coarse
phasing of the segments under maintenance.
As segments integration starts
after most major subsystems have been
completed and provisionally accepted
on-site, first light may follow rapidly. According
to current estimates, science
could start within 19 months after the integration
of the first segment, with a total
collecting area equivalent to that of a
50-m telescope.
The estimated schedule to completion is
currently under thorough review. The
baseline plan would allow first light five
years after construction begin, start
of science one year later and completion
11 years after construction start. The
critical path to first light is set by the structure,
enclosure, and above all the 8-m
mirrors of the corrector and the first generation,
2.3-m class adaptive mirror. Options
are currently being explored, whereby
early financial commitments would
allow for a faster schedule. Such commitments
would represent roughly 5 % of
the total capital investment, and include,
most notably, the early purchase of
two 8-m blanks, and of competitive final
designs of the structure, enclosure,
and first generation adaptive unit. A higher
cash flow in the early phases of construction
would also be necessary.
Several concept studies on OWL instrumentation
have begun, in close collaboration
with the astronomical community
(most of them are carried out outside
ESO), to explore the requirements imposed
on instruments by the science cases,
and the related feasibility issues. Specific
instrument-related science cases are
also being developed, in close contact
with the other science activities described
earlier.
ELT Design Study
During 2004, substantial effort has been put
into the negotiation of the final scope of
work and budget for the ELT Design Study. The
project, approved for partial funding by the
European Commission, covers the development
of enabling technologies and concepts for an
Extremely Large Telescope, without prejudice to
its actual design. As such, the activities covered
by this project are complementary with those
specifically undertaken for the design of OWL.
The design and testing of position actuators, of
metrology systems, the development of breadboards
for the evaluation of performance under
wind excitation, for the on-sky evaluation of
wavefront control techniques including phasing
(APE), prototyping of thin adaptive shells,
site characterization, etc. are typical examples
of tasks covered by the ELT Design Study.
As parallel, but not redundant activities, the
OWL design and the ELT Design Study benefit
from mutual feedback, their respective schedules
ensure that progress is made in an optimized
timeframe, and their complementarities
ensure cost-effective developments. Indeed the
parallelization of activities is crucial, as delays
in the ELT Design Study would potentially delay
design and analysis activities with OWL, and
vice-versa.
The ELT Design Study gathers 30 partners,
mostly European, and including academic
as well as industrial resources, under ESO’s
lead. The proposal was submitted to the
EC in March 2004, and received very high
marks. The total project cost was estimated at
42 M€, out of which 22 M€ were requested
to the EC. It was approved at a level 8.4 M€ in
EC funding i.e. 14 M€ lower than initially requested.
Utmost effort has been undertaken by
most partners in order to cut costs without
significant de-scoping, as requested by the EC,
and to maintain the level of self funding at
the pre-cut values. This included increasing the
ESO contribution to 9.4 M€.
OWL Instruments
In support of the on-going OWL Feasibility
Study, several Instrument Concept studies have
also been started by the Instrumentation
division with the astronomical and technical
support of institutes in France, Germany,
Italy, The Netherlands, Sweden, Switzerland
and the United Kingdom. The capabilities
being explored include an ultra-stable, high resolution,
optical spectrograph to measure the
cosmic expansion from the observation of high
redshift sources; a wide field camera with partial
adaptive optics atmospheric correction for
the study of faint stars and galaxies; a multiobject,
near IR spectrograph; a small field, diffraction
limited planetary camera-spectrograph
for the detection of earth-like planets; a submillimetre
camera for the detection and study of
dusty, high redshift star forming galaxies; a
thermal infrared camera-spectrograph for the
investigation of regions of star formation in
the Galaxy and at high redshift, and an instrument
for the study of quantum optics phenomena
in astrophysics. The specific purpose
of these studies is to elaborate on the science
goals which are expected to make the
largest impact; test the viability of building
the required instruments and interfacing them
with the telescope; identify any required technical
developments and provide a rough idea of
possible costs. More generally, this exercise
will make the ESO community more familiar with
the OWL concept and provide them with the
opportunity to contribute actively to its detailed
definition and design.
0.6�
1.7�
ESO Annual Report 2004
Simulated point spread
function in K-band, with
residual phasing errors,
under good seeing conditions,
with bright guide
star (m K = 8) and single
conjugate adaptive
optics (first generation).
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