The Atacama Large Millimeter/submillimeter Array (ALMA), an immense international telescope project under construction in northern Chile, reached a major milestone on April 30, when two ALMA antennas were linked together as an integrated system to observe an astronomical object for the first time.
The milestone achievement, technically termed "First Fringes," came at ALMA’s Operations Support Facility, 9,500 feet above sea level.
Faint radio waves emitted by the planet Mars were collected by the two 12-meter diameter ALMA antennas, then processed by state-of-the-art electronics to turn the two antennas into a single, high-resolution telescope system, called an interferometer.
Such pairs of antennas are the basic building blocks of imaging systems that enable radio telescopes to deliver pictures that approach or even exceed the resolving power of visible light telescopes. In such a system, each antenna is combined electronically with every other antenna to form a multitude of antenna pairs. Each pair contributes unique information that is used to build a highly-detailed image of the astronomical object under observation.
When completed early in the next decade, ALMA’s 66 antennas will provide over a thousand such antenna pairings, with distances between antennas exceeding ten miles. This will enable ALMA to see with a sharpness surpassing that of the best space telescopes. The antennas will operate at an altitude of 16,500 feet, high above the OSF, in one of the best locations on Earth for millimeter-wavelength astronomy, the Chajnantor Plateau in Chile’s Atacama Desert.
Last week’s successful Mars observation was conducted at an observing frequency of 104.2 GHz. Astronomers measured the distinctive varying “fringes” detected by the interferometer as the planet moved across the sky.
“This is a great success,” said Adrian Russell, North American ALMA Project Director at the National Radio Astronomy Observatory (NRAO), “not because we observed a naked-eye planet, but because we observed something in the sky interferometrically using the genuine hardware that soon will be making its way up to the mountain to the Array Operations Site. Components from North America, Asia, and Europe are all working together to form a single mammoth telescope, and that bodes well for ALMA’s success.”
“This can only be achieved with the perfect synchronization of the antennas and the electronic equipment: a precision much better than one millionth of a millionth of a second between equipment located many kilometers apart. The extreme environment where the ALMA observatory is located, with its strong winds, high altitude, and wide range of temperatures, just adds to the complexity of the observatory and to the fascinating engineering challenges we face,” commented Richard Murowinski, ALMA Project Engineer at the Joint ALMA Observatory (JAO) in Chile.
ALMA will provide astronomers with the world's most advanced tool for exploring the Universe at millimeter and submillimeter wavelengths. It will detect fainter objects and be able to produce much higher-quality images at these wavelengths than any previous telescope system. Scientists are eager to use this transformational capability to study stars and galaxies that formed in the early Universe, to learn long-sought details about how stars are born, and to trace the motion of gas and dust as it whirls toward the surface of newly-formed stars and planets.
“This is another important step forward for ALMA as it proves that the various hardware components can work well together. The efforts of all the staff involved in this first antenna integration show the strength of our global collaboration and give much confidence that we can get to full operations with ALMA as one great astronomical observatory,” said Thijs de Graauw, ALMA Director at the JAO. “We are on target to do the first interferometry tests at the 5000-meter-high site by the end of this year, and by the end of 2011 we plan to have at least 16 antennas working together as a single giant telescope.”
The ALMA Project is a partnership between the scientific communities of East Asia, Europe and North America with Chile.ALMA is funded in North America by the U.S. National Science Foundation in cooperation with the National Research Council of Canada and the National Science Council of Taiwan. ALMA construction and operations are led on behalf of North America by the National Radio Astronomy Observatory, which is operated under cooperative agreement by Associated Universities, Inc.
With ALMA, astronomers will study the cool Universe: the molecular gas and dust that constitute the building blocks of stars, planetary systems, galaxies, and of life itself, providing new and necessary information on the creation of stars and planets. It will also reveal distant galaxies from the primal universe that we will see as they were more than ten billion years ago, representing not only an important observation instrument for scientists, but also a new cosmic vision for humanity.
The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Southern Observatory (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan. ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.