ALMA is the largest ground-based observatory in the millimeter and submillimeter regime and one of the largest astronomical facilities in the world. The interferometer's 66 telescopes with diameters of 7 and 12 meters, are located at 5000 meters altitude in northern Chile on the Chajnantur plateau. ALMA is a collaboration between Europe, the US, Japan and Chile.
ALMA (Atacama Large Millimeter/submillimeter Array) enables research into the physics of the 'cold universe', such as the study of the formation of planets and the first stars and galaxies.
ALMA is a premier tool for studying the first stars and galaxies that emerged from the cosmic "dark ages" billions of years ago. The light from these objects at great cosmic distances, is stretched out to millimeter and sub millimeter wavelengths by the expansion of the Universe.
In the more nearby Universe, ALMA provides an unprecedented ability to study the processes of star and planet formation. Unimpeded by the dust that obscures visible-light observations, ALMA is able to reveal the details of young, still-forming stars, and shows young planets still in the process of developing.
In addition, ALMA allows scientists to learn in detail about the complex chemistry of the giant clouds of gas and dust that spawn stars and planetary systems.
The construction of ALMA was completed in 2013, but the first scientific observations were already done in 2011. Each of ALMA's 66 telescopes is equipped with 10 different frequency band receivers for observations, ranging from 84 GHz to about 950 GHz, corresponding to 3.6 - 0.3 mm wavelength. Most receivers are based on SIS heterodyne mixers, enabling high resolution spectroscopic observations.
The NOVA-ALMA group at SRON Groningen was contracted for the development and realization of 66 Band 9 receivers in 2003 and for the same amount of Band 5 receivers in 2012.
The Band 9 receivers observe in the high frequencies, from 602 - 720 GHz, corresponding to 0.42 - 0.50 mm wavelength. The high altitude location of ALMA was mainly selected for these very high frequency band receivers, that enable high spectral resolution, since higher spectral resolution is obtained with shorter wavelengths.
The Band 5 receivers observe the universe in the 163-211 GHz frequencies, corresponding to wavelengths of 1.42-1.84 mm. This is the only frequency band or wavelength band in which water can be detected from the ground, behind Earth’s atmosphere. Band 5 therefore increases the capabilities of the ALMA telescope to search the cosmos for water and the conditions needed for life.
Sixty percent of the Band 5 receivers has been installed on ALMA in 2017. The NOVA-ALMA group will complete the Band 5 project by the end of 2017.
The Band 5 and Band 9 receivers use detector technology legacy of SRON's molecule detecting instrument HIFI, on board the Herschel space telescope (ESA).