Untitled - ESO

Atacama Large Millimeter/submillimeter Array
The Atacama Large Millimeter/submillimeter
Array (ALMA) is a very sensitive,
high-resolution aperture-synthesis array
telescope, which will work at millimetre
and submillimetre wavelengths. It is an
international facility, constructed and
operated as a partnership between
Europe (through ESO), North America
(through the National Radio Astronomy
Observatory, NRAO) and Japan (through
the National Astronomical Observatory of
Japan, NAOJ), in cooperation with the
Republic of Chile.
The initial plan was to install and operate
64 antennas of 1 metres diameter, but
detailed design studies and prototype
research showed that this project could
not be realised with the funds foreseen
by the agreement between the North
American and European partners. During
005, in-depth studies were made to
redefine the ALMA baseline project with
acceptable cost, while still maintaining
the prime scientific objectives. By the
middle of 006, the North American
partners received approval from their
Funding Agency (the US National Science
Foundation, NSF) for the rebaselined
ALMA project, which had already been
approved by ESO Council towards the
end of 005.
In parallel, Japanese scientists, through
the NAOJ, continued to define their
participation in the ALMA project. The
European and North American partners
in ALMA spent a considerable amount of
time with their Japanese partners in
identifying the Japanese participation and
reviewed various subsystems, in particular
the correlator, receivers and antennas.
Details of the partnerships were defined
and a trilateral agreement between ESO,
the NSF, and the National Institute for
Natural Sciences (NINS, Japan) was
signed in summer 006. In addition to the
equipment that NAOJ will provide for the
bilateral ALMA configuration of 50
antennas, NAOJ will provide four antennas
of 1 metre diameter, twelve antennas
of 7 metre diameter, and two receiver
bands for all 66 antennas of ALMA.
Approval of funds required for the
Japanese participation in ALMA is
38
ESO Annual Report 006
expected by spring 007. With the
inclusion of the Japanese partners,
ALMA becomes a truly global astronomy
facility, involving scientists from four
different continents.
Construction Work
The ALMA Array Operations Site (AOS)
will be located at a truly unique and
unusual place: the Altiplano de Chajnantor,
a plateau at an altitude of 5 000
metres above sea level, in the Atacama
Desert in Chile. This location was
selected for scientific reasons, particularly
dryness and altitude. Considering
these aspects, the ALMA Observatory
will not only be unique because of its
ambitious scientific goals and the
unprecedented technical requirements.
It will also be unique because of the
harsh environment and living conditions
in which the array has to operate with
high efficiency and accuracy.
A second site, the ALMA Operations
Support Facilities (OSF), will be the base
camp for the day-to-day operation of the
observatory. It is located at an altitude of
about 900 metres, quite high compared
to standard living conditions, but still
acceptable for scientific projects in
astronomy of similar scope. However, the
OSF will not only serve as the location for
operating the ALMA Observatory: it will
also be the site for Assembly, Integration
and Verification (AIV) of all the hightechnology
equipment before this is
moved to the Array Operations Site.
The AOS Technical Building.
Both the AOS and OSF are remote
locations. The 900-metre OSF site is
about 15 kilometres away from the
closest public road, the Chilean highway
No. 3. The AOS is another 8 kilometres
away from the OSF site. Thus, one of the
first ALMA projects was to construct an
access road not only to the OSF but also
to the AOS. This road, 43 kilometres long
and at high altitude, with sufficient width
for the regular transport of many large
radio telescopes with diameters of 1
metres, was completed in the course of
006.
The OSF is in many ways the centre of
activities of the ALMA project, and will
remain so in the future. The focus there
will, however, change as ALMA moves
through the different phases of construction
and operations.
Presently, the OSF site is the area where
all ALMA Site contractors and their staff
are accommodated – the base camp for
work on the OSF and AOS infrastructure.
Local contractors’ staff live there and
start their work either at the OSF, the
road construction (between the Chilean
Highway No. 3 and the AOS) or at the
AOS itself. Work is organised in 0 days
working/10 days rest periods. Special
facilities for board and lodging have had
to be organised for such a large activity.
Camps have been erected and by now
can accommodate the maximum
required capacity of 500 workers.