Sol Lucet Omnibus - ESO

Seiichi Sakamoto
Born in Tokyo, Japan
Biography
Seiichi believes it is important to take a scientific approach to many aspects of life. He also
advocates that astronomers educate the public about not only the wonder of astronomy, but also
the positive impact it has on our lives. To this end he is keen to communicate his work and that
of other scientists to people from all walks of life. Seiichi’s enthusiasm and honest work ethic has
earned him the respect of many.
Seiichi’s major research field is in radio astronomy and interstellar physics. He participated in
the planning and construction of the Atacama Large Millimeter and submillimeter Array (ALMA).
Seiichi currently works for JAXA as Director for Space Science Outreach at the Institute of Space
and Astronautical Science (ISAS). He is an experienced astronomer and project coordinator, with
many initiatives to his name.
Japan Aerospace Exploration Agency, Institute of Space and Astronautical Science (JAXA/ISAS)
JAXA was established in October 2003 as an independent administrative institution, by
integrating the Institute of Space and Astronautical Science (ISAS), the National Space
Development Agency of Japan (NASDA) and the National Aerospace Laboratory of Japan (NAL).
ISAS became one of four principal sections of JAXA. Its mission is to advance space science
— scientific research conducted in outer space — in Japan, mainly by collaboration with
universities. It also actively contributes to JAXA’s and Japan’s entire space development.
www.isas.jaxa.jp
Selecting the Best Site for an
Observatory
Professional observatories are
our windows to the Universe,
but finding the right place to
build these colossal structures is
a science in itself. Here, Seiichi
Sakamoto talks us through the
process of site selection, using
the high-tech Atacama Large
Millimeter/submillimeter Array as
a case study.
Japanese site-testing equipment at the ALMA site in northern
Chile. Containers, solar cells and some of the equipment are
visible.
The Earth’s atmosphere absorbs, scatters and scintillates the signals from
celestial bodies. Space is an ideal site for observations, but naturally has
budgetary and technical constraints. Practically speaking, instruments
much heavier than a few tons have so far been difficult to launch, and so
ground-based facilities are vital. There is much literature on the importance
of the scientific instruments; I will focus on the practical selection
procedures of the site where the instruments are to be installed.
Astronomers love dry, high sites far away from
cities
The requirements for a “good” site for astronomical observations depend
on what you would like to observe. In general, a site for an astronomical
project should be good in terms of atmosphere and geography.
The atmospheric factors include atmospheric transparency, seeing,
meteorological conditions (e.g. surface wind, snowfall, near-surface
temperature, lightning safety) and sky brightness. Geographical and
geological conditions include local topography (i.e. slope, roughness),
seismicity, mechanical/electric/thermal properties of rocks/soils, and
available sky coverage due to latitude and skyline.
Other issues such as existing infrastructure, accessibility, status of the
host country (e.g. political status, environmental issues, satisfactory
agreements, and labour level), construction cost and ease of getting funds
sometimes play major roles in determination of the site. The scores and
relative weighting of these conditions depend on the scientific objectives,
specifications and cost of the instrument, as well as who is to promote and
who is to fund. Even more complicated, they are often time variable and
need to be modified within the boundaries of given budget, schedule, and
manpower of the project.
17