Large Latin American Millimeter Array


The Large Latin American Millimeter Array is a single-dish 12 m Nasmyth optics antenna which is under construction in the Puna de Atacama desert in the Province of Salta, Argentina. The primary mirror accuracy will allow observation from 40 GHz up to 900 GHz. It is also planned to install a bolometer camera at millimeter wavelengths. After installation it will be able to join other similar instruments to perform Very Large Base Line Interferometry or to work in standalone mode. Financial support is provided by the Argentinian and Brazilian governments. The total cost of construction, around US$20 million, and operation as well as the telescope time use will be shared equally by the two countries. Construction planning started in July 2014 after the formal signature of an agreement between the main institutions involved.

Overview

LLAMA is a joint project between Argentinian and Brazilian Astronomers to build and operate a radio telescope at submillimeter wavelengths, that can work in stand alone mode or join a Very Long Baseline Interferometry network. The main scientific institutions involved in the project are the Argentine Institute of Radio Astronomy, and the Núcleo para o Apoio da Rádio Astronomia, from the Universidade de São Paulo. The telescope is located at a very high altitude where the atmospheric absorption allows the observation at the very short wavelengths of less than 1 mm. It is a multipurpose instrument that will have cryogenic receivers with very high sensitivity in order to observe very faint sources, and filters to observe the Sun.

History

The history of the instrument can be traced back to 2007, during the XII Latin American Regional IAU Meeting held in Isla de Margarita. Argentinian radio astronomers discussed the idea with colleagues from South America. The search for the best place for a submillimeter telescope had started in Argentina in 2003, with a 210 GHz tipper which was installed in different places to investigate the atmospheric opacity. During the XXVII General Assembly in Rio de Janeiro, the project gained a name in a document authored by the leading scientists of the project. In the same document, scientists also proposed the initial science, budget, strategies for construction, site, and other matters. The formal presentation before the Argentinian Science Ministry was in 2010, while a meeting held at the offices of FAPESP in August 2011 was the kickoff in Brazil. In 2011, MinCyT ranked LLAMA as its astronomical project and in 2012, FAPESP approved a €7 M grant. The final agreement, between MinCyT, FAPESP and Universidade de São Paulo, was signed in June 2014, and on July 9, it was formally presented to the public.
Measurements of the electrical characteristics of the site were carried out in late 2016, and construction of the road to the summit began in December 2016.

Origin of the name

The observatory acronym comes from the Quechuan word llama that designates the South American camelid that lives in the region where the telescope is being installed. There is some confusion with the word array, since LLAMA will consist of a single dish antenna, but the instrument will have VLBI technology and can therefore be part of an antenna array with telescopes of other observatories. Moreover, the LLAMA observatory can be expanded in the future by installing other antennas in different sites.
In different official documents the acronym LLAMA may be found expanded as Long Latin American Millimeter Array rather than Large. It is also possible to read Millimetric instead of Millimeter. After some debate, the LLAMA Executive Committee stated that Large Latin American Millimeter Array is the right expansion for the LLAMA acronym.
The observatory logo has as symbols the Southern Cross, a telescope sketch, the acronym and a llama profile. Although it changed with time, these symbols are present since the beginning. The image illustrating this page is the official logo since August 2014.

Science

LLAMA is a multipurpose instrument, with the capacity to both observe bright sources like the Sun, and very weak sources very far from Earth. The following is a list of different subjects that will be addressed with LLAMA observations.

The Sun

In the unperturbed solar atmosphere, the shorter the wavelength the deeper the observation. Frequencies near the submillimeter range are produced in the lower chromosphere or the photosphere. Therefore, LLAMA observations will bring new information about the structure of the lower Solar Atmosphere, the active and quiescent filaments and the dynamics of the Chromosphere and its Magnetic Field. The possibility to observe Solar Flares at high frequencies with a high sensitive instrument will give clues about the acceleration of the high energetic particles in the Sun, complementing results obtained with the Solar Submillimeter Telescope. In particular the still unexplained spectral inversion above ≈ 100 GHz. A possible experiment would be to make VLBI solar observations. For example, in a joint observation between LLAMA and some of the ALMA antennas, a spatial resolution of 0.001" would be achieved for λ ≈ 1 mm, corresponding to a distance of 700 m on the solar surface.

Planets

Optics, Receivers

The Nasmyth optics will allow the installation of up to as six different heterodyne receivers. There is a consensus for these receivers to use the same spectral bands as ALMA. With this scheme the Nasmyth cabins will allocate receivers for the bands
#Frequency Band Wavelength Band
135 - 508.6 - 6.0
384 - 1163.6 - 2.6
5162 - 2111.9 - 1.4
6211 - 2751.4 - 1.1
7275 - 3731.1 - 0.8
9602 - 7200.5 - 0.4

It is intended to install a bolometer multi-wavelength camera at the Cassegrain focus, or possibly a camera plus a small heterodyne array.