ALMA: A look into the universe’s soul
ALMA, or “soul” in Spanish, is the name of the world’s largest telescope, located over 5,000 metres above sea level in the Atacama desert, Chile. The facility’s 66 mobile parabozlic antennas provide ALMA with a variable diameter that ranges from 150 metres to 16 kilometres. This serves as a gigantic zoom lens and allows the telescope to peer deep into the universe’s soul. ALMA will be officially inaugurated on 13 March 2013. At its heart lie fiber optic connections from HUBER+SUHNER.
The abbreviation ALMA actually stands for Atacama Large Millimeter Array. The installation site was chosen for a very specific reason: the Atacama is the world’s driest desert, the Chajnantor plateau is flat and lies 5100 metres above sea level. No other place on Earth offers a clearer view of the stars. Institutions from North America, Japan and Europe are working together at this location to discover how the very first galaxies formed in the early universe.
66 antennas – one telescope
ALMA is what is referred to as an “array” telescope. Instead of one massive parabolic antenna, it is comprised of 66 individual satellite dishes, most of which have a diameter of just 12 metres. Some are even 7 metres or smaller. They can, however, be distributed across the Chajnantor Plateau in different configurations and, when taken together, form one gigantic telescope. The diameter of this mega-telescope varies from 150 metres to 16 kilometres, with the mobile antennas acting as a type of zoom lens. The researchers can rearrange the dishes to give them the best view of the object they are currently interested in. The antennas, which each weigh over 100 tonnes, are moved on a rotating basis by two gigantic transporters. This allows some antennas to be relocated each day while the remainder continue to operate and provide information. Over a period of months, the entire array can be reconfigured from a compact arrangement to a distributed group, and vice versa.
Interferometry with LiSA and MASTERLINE
In order for the numerous antennas, which operate at millimeter wavelengths, to function as a single unit, they need to be linked together and their various signals merged into one. This process is referred to as interferometry and requires the utmost precision. To this end, 191 concrete pedestals that allow the antennas to be anchored with millimetre accuracy are distributed across the plateau. The pedestals are connected to the power supply and a fiber optic network for collating the signals emitted by the various telescopes. This star-shaped network centres around a technology building on the antenna field. And, at the heart of this building at a height of 5,100 metres, you can find earthquake-resistant LiSA cabinets from HUBER+SUHNER. Here, the fiber optic cables converge before splitting again in some cases. They are then distributed to the active systems of the central computer using preassembled MASTERLINE fiber optic cable systems, also from HUBER+SUHNER. These systems are highly robust and are able to withstand the low temperatures that can cause problems at such heights. They also have extremely low fiber length tolerances to prevent time differences occurring during signal transfer that could have a detrimental effect on interferometry. Since all connections need to be reattached whenever the dishes are moved to a new position, the plug-and-play concept greatly simplifies the relocation of individual antennas.
Data centre at just 2,900 metres
Since neither humans nor computers are able to operate effectively above 5,000 metres, the massive amounts of data generated are processed and analysed at a different location. The bundled signals are therefore transferred through a fiber optic connection to a data centre 28 kilometres away that lies just 2,900 metres above sea level. Upon arrival, they are analysed by a host of high-performance computers and around 500 astronomers and engineers. To facilitate this, the incoming signals pass through another set of LiSA distribution cabinets and MASTERLINE cable systems from HUBER+SUHNER. Together, these provide a complete, customer-specific solution for all passive fiber optic components used at ALMA, including support.
Inauguration on 13 March 2013
It has, however, taken a long time to reach this stage. The first surveys of the Chajnantor Plateau were conducted in the mid-1990s. Once it had been determined that the location was suitable, North America, Japan and Europe agreed to joint implementation of the project in 2001. Construction started in November 2003. It was not possible to obtain the first scientific readings until 2011, and this was with a heavily reduced infrastructure. The official inauguration ceremony for ALMA will be held on 13 March 2013, almost ten years after the start of construction. Only then will it enter full operation. By this date, all 66 antennas will be on site, mostly in operational use, as well as all main systems in the observatory. The entire team will also start work on the project, from system maintenance to research. Only then will ALMA be able to take up its true calling: revealing the soul of our universe.