Broad Atacama Millimeter Array
ALMA ( Broad Atacama Millimeter Array ) is currently a Interféromètre radio in the fields millimetre-length and submillimeter (in atmospheric windows between 80 and ~600 GHz) in the course of construction with the Chile. This one is localized with an about sixty kilometers in the east of the town of San Pedro de Atacama, on the site of Llano de Chanjnator, a high plateau of the desert of Atacama (5100 m). It is there that already the radio telescope APEX is.
This project being nowadays one of most ambitious in the field of the astronomical observation , (after those relating to the Broad Very Telescopes and the James Webb Space Telescope), this one concerns the international cooperation. The initial budget is about 700 half, Dollar million/half between Europe (through the ESO) and USA (by the NFS and NRAO). Interferometer ALMA should include/understand about 50 to 64 antennas 12 meters in diameter, without counting the dozen antennas of 8 meters brought to the project by the Japanese.
Project ALMA
Objectives
ALMA falls under the field of the Radioastronomie: the study of space rests not only on the study of images acquired by the telescopes but also on the study of the Ondes (and in particular of the spectrum) emitted by the interstellar objects. One speaks about Spectroscopie. The latter is necessary in order to discover the composition of these objects and to include/understand the way in which they are formed and evolved/moved. Thus, the purpose of this project is the observation of various phenomena in order to better include/understand our Univers. Here inter alia which will be its main subjects of research:- the study of the young Universe through the observation of Galaxy S distant
- the study of the formation of the star S through the observation of the molecular clouds (such as for example that of Orion)
- the study of the formation of the Planet S
- the search for Exoplanète S by Astrometry
- the study of our solar system resting on the study of dust and that of the atmospheres of various planets like Mars and Venus (this last subject will make it possible for example to have a better idea of their atmospheric dynamics or to detect a presence of water)
Means
In order to allow these various observations, it is necessary to join together a certain number of conditions.- First of all, the study of millimetre-length and submillimeter waves requires a dry environment. Indeed, these waves are mainly absorbed by the steam present in the atmosphere, which explains the choice of this arid plate to 5.000 m of altitude.
- Moreover, to have such a power of observation there exist two possibilities: either creation of enormous Radio telescope (such as for example that of Arecibo to Puerto Rico which measures 305 m in diameter), or the construction of a network of several antennas, i.e. an interferometer (such as for example the Broad Very Array close to Soccoro to the New Mexico, or that of the plate of Bore-hole in the French Alps). It is the second option which was selected. In the long term this one should be made up of 64 antennas 12 m in diameter each one, the whole gathered on a surface whose more basic broad outline is of 14 km and whose smallest is of 150 Mr. the unit will be entirely installed from here 2012, but it is possible that limited observations start as from 2008 with the 6 to 8 operational antennas at this time.
Budget
The key point of project ALMA is the cost of the antennas, which represents approximately half of the total costs of the project. What gives unit costs of these antennas of 12 m to submillimeter capacity to 5.5 M $ part. An antenna of the IRAM, 15 m but without submillimeter capacity, is about 30 M Frank, that is to say 4.6 M of Euro part.
The total budget announced in 2001 was approximately 550 million dollars (sky and space of June 2007 speak about 1.3 billion $). In 2005, it seems that a overcost of about 20% is inevitable, while being today able to finance only 50 antennas. The initial budget of phase 1 (development of prototypes of antennas) was estimated at 26 million dollars financed on the American side and at 15 million euro on the European side.
Partners
Because of the importance of the project, ALMA is a partnership between Europe and North America, in co-operation with Chile. Europe is represented by the southern European Observatoire (European Southern Observatory: ESO) and Spain should benefit from it to adhere to the ESO. North America is represented by the the National Science Foundation (the United States) and the National Research Council (Canada). Japan also takes part in the project, but contributes its share in kind (12 small antennas and a correlator).
See too
Internal bonds
- APEX (Atacama Pathfinder EXperiment)
External bonds
- Web site ALMA