The Atacama Large Millimeter/submillimeter Array (ALMA) is the largest astronomical project in existence, and the world's most powerful telescope for studying the universe at submillimetre and millimetre wavelengths (0.3 mm to 9.6 mm). Composed of 66 reconfigurable high-precision antennas, ALMA is located on the Chajnantor plateau of the Chilean Andes at an elevation of 5,000 metres above sea level.
ALMA offers unprecedented sensitivity and imaging capabilities, enabling astronomers to create highly detailed images of sources of millimetre and submillimetre emission. Phenomena that were previously out of reach can now be observed, including probes of the very first stars and galaxies. The facility is a complete imaging and spectroscopic instrument for the millimetre/submillimetre regime, providing scientists with state of the art capabilities and wavelength coverage.
The main array has 50 antennas, each 12 metres in diameter, acting together as an interferometer. An additional compact array of four 12-metre and twelve 7-metre antennas complements the main array. The ALMA antennas can be arranged in different configurations, giving ALMA a powerful variable zoom, and a resolution that can be up to ten times better than the Hubble Space Telescope. To process the signals received, ALMA relies on two correlator sub-systems; one for the main array, and one for the compact array.
All of ALMA's antennas work in concert, taking either quick "snapshots" or long-term exposures of astronomical objects. Cosmic millimetre waves from these objects are reflected up from the surface of each dish to the sub-reflector above each dish's centre. From there, they are guided down into highly sensitive receivers operating at -269 °C. The receivers amplify these signals many millions of times, before digitizing them and sending them along fibre-optic cables to a large signal processor, the correlator. This machine combines the signals to produce data from which images of remarkable quality can be made. In its widest configuration, the image detail provided by the completed array is comparable to that of a single radio telescope 14 km in diameter.
Access and use
ALMA is designed for all astronomers, planetary scientists, astrophysicists, and other astronomy-related scientists. Scientists compete for observing time by submitting proposals, which are then judged on the basis of scientific merit. Canadian principal investigators may apply without restriction for North American time, presently 37.5% of the total available.
Proposals are solicited approximately once per year as "cycles" with calls approved by the Joint ALMA Observatory Board. To receive notification of future calls for proposals, register with the ALMA Science Portal, to connect with your ALMA Regional Centre (ARC). Astronomers at Canadian institutions are supported by the North American ALMA Science Center (NAASC) based in Charlottesville, VA and with additional support from a team based at NRC's Dominion Astronomical Observatory (DAO) in Victoria, BC.
Call for observation proposals
The latest information about recent calls for proposals is available on the ALMA Science Portal. The Portal also contains additional resources including the ALMA Primer, produced by the NRC for the ALMA partnership.
Time allocation process
To use the ALMA Helpdesk, or to submit (or co-author) a proposal, users must register with the ALMA Science Portal.
All proposals are subject to peer review by an international committee and are assessed on their scientific merit. Planned observations must be consistent with available capabilities and must be fully technically justified.