News

Copyright: ALMA (ESO/NAOJ/NRAO, Alvaro Quintana and Jose Olivares (ALMA)

The Atacama Large Millimeter/Submillimeter Array (ALMA) has achieved an important milestone when the first two 12m antennas installed at the 5000m altitude site have been successfully connected in interferometric mode. This is a critical step in the construction and deployment of this extremely large array, consisting in a total of 66 twelve and seven meter antennas to be installed on the Chajnantor plateau in northern Chile.

ALMA is a world-wide collaboration between North America, Europe and Eastern Asia and is the largest ground-based astronomical instrument currently in construction. In Europe, the ALMA project is funded and managed by ESO, the European Southern Observatory. With its highly recognized expertise, IRAM is one of the major partners in the construction of ALMA and is in charge of the development and production of several key elements of the instrument, such as the band 7 (275-373 GHz) receivers, the correlator digitizer clocks and the real-time calibration software (TelCal).

 

Copyright: ALMA (ESO/NAOJ/NRAO)

On November 5th 2009, first fringes on the high-altitude site were obtained with the band 7 receivers (see figure), measuring the continuum emission of a bright quasar, 3C454.3. The result testifies for the high quality and performances of IRAM receivers, which exhibit noise figures well below the initial ALMA specifications. A copy of the band 7 receiver is installed at the IRAM 30m telescope (band 4 of the EMIR receiver). The Plateau de Bure interferometer will soon be equipped with similar receivers.

 

Design of the ALMA Band 7 cartridge; Copyright: IRAM

The development and construction of (sub)millimeter receivers is a highly demanding task, that requires careful design and complex work in clean rooms and laboratories. IRAM is one of the few institutes on the planet that masters all steps of the design and construction of such equipments.

Another key element used to obtain the first ALMA fringes is the TelCal ("telescope calibration") software, which is performing the real-time calibration of the instrument, making sure the array is properly tuned and able to observe. TelCal is also pre-processing the incoming data and will, in the future, apply the real-time atmospheric correction. The expertise acquired with the Plateau de Bure interferometer has been widely used to develop this new software, which is written by a team of software engineers at IRAM.

Note also that the astronomers and engineers team that obtained the first ALMA fringes in Chile was led by Robert Lucas, who has spent more than 20 years at IRAM before joining the ALMA Commissioning team.

 

For more information about IRAM and ALMA click here:

IRAM developments for ALMA

IRAM ARC Node
 

For more information about ALMA:

ALMA observatory

ESO ALMA pages