How ALMA Observations are carried out


Scientists from all over the world use ALMA.

ALMA will operate for half a century, and it will be used by several generations, including those who are currently elementary and junior high school students.

10% of observation time is allocated to the host country, Chile, and 90% for the partners, according to their financial contribution to ALMA. Although proposals are accepted by researchers from all over the world, special consideration is given to those coming from partner countries of the project.

Another important aspect is that ALMA is designed not only for astronomers but also for planetary scientists, physicists and other scientists whose studies are associated with astronomy.


The scientists compete for observing time by submitting proposals, which are assessed, on the basis of scientific merit only, by an external Scientific Committee (the researcher’s name is not disclosed to the judges at that point).

Researchers from the selected projects do not travel to Chajnantor to carry out the observations. Instead, these are carried out 24 hours per day by ALMA astronomers, working at the Operations Support Facility. Observations are dynamically scheduled, depending on weather conditions and the antenna array configuration, and data are then transmitted, via fiber optics, to the ALMA Regional Centers (ARCs), who, in turn, deliver them to the project’s Principal Investigator.

Each of the three ALMA partners is given the right to decide on time allocation, but some key projects may be launched for international coordination, such as projects that seek to observe galaxy formation and planetary construction.


The Joint ALMA Observatory (JAO) issues the calls for proposals for scientists from around the world to submit their proposals for observation time. The JAO, with assistance from the ARCs, coordinate the refereeing process. The cycles of observation carried out by ALMA are as follows:

Cycle 0 (Preliminary observations with 16 antennae): September 2011 to January 2013

Cycle 1 (Early Science with 43 antennas): Early 2013.

Cycle 2 (Early Science with 45 antennas): As from June 2014.

Cycle 3 (Early Science with 48 antennas): As from October 2015.

Cycle 4 (Science with 53 antennas): As from October 2016.

Cycle 5 (Science with 56 antennas): As from October 2017.

What about the data produced?: ALMA Public Archive

The data produced during an ALMA observing run, as well as their calibrations, are stored in the ALMA Archive, located at the headquarters in Santiago, and copied fully by the ARC’s. Once the observatory reaches its full capability, storage will increase to a range of 80 Gigabytes per day.  Stored data will eventually become public, but not immediately.

Scientists who are allocated observing time with ALMA are granted exclusive access to the gathered data for one year. This period is known as “proprietary period”, which starts when the data are distributed to the Principal Investigator. After this period has elapsed, the data becomes public at the ALMA Archive and any investigator can retrieve them through the ALMA science website. However, for this you must make a request directly to the ARCs, ALMA’s partners with the scientific world.

The date retrieved through observations are the primary source of new discoveries. It is expected that this archive will have a life of its own and become a treasure of information for all humankind.

Archive in ARC ESO

Archive in ARC NRAO

Archive in ARC NAOJ

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