The Atacama Large Millimeter/Submillimeter Array (ALMA), an international telescope project, reached a major milestone on March 2, when two ALMA prototype antennae were first linked together as an integrated system to observe an astronomical object.
The milestone achievement, technically termed “First Fringes,” came at the ALMA Test Facility (ATF) on the grounds of the National Radio Astronomy Observatory’s (NRAO) Very Large Array (VLA) radio telescope in New Mexico. NRAO is a facility of the National Science Foundation (NSF), managed by Associated Universities, Incorporated (AUI). AUI also is designated by NSF as the North American Executive for ALMA.
Faint radio waves emitted by the planet Saturn were collected by the two ALMA antennae, then processed by new, state-of-the-art electronics to turn the two antennae into a single, high-resolution telescope system, called an interferometer.
Such pairs of antennae are the basic building blocks of multi-antenna imaging systems such as ALMA and the VLA. In such a system, each antenna is combined electronically with every other antenna to form a multitude of pairs. Each pair contributes unique information that is used to build a highly-detailed image of the astronomical object under observation. When completed in 2012, ALMA will have 66 antennae.
The successful Saturn observation began at 7:13 p.m., U.S. Mountain Time Friday (0213 UTC Saturday). The planet’s radio emissions at a frequency of 104 GigaHertz (GHz) were tracked by the ALMA system for more than an hour.
“Our congratulations go to the dedicated team of scientists, engineers and technicians who produced this groundbreaking achievement for ALMA. Much hard work and many long hours went into this effort, and we appreciate it all. This team should be very proud today,” says NRAO Director Fred K.Y. Lo. “With this milestone behind us, we now can proceed with increased confidence toward completing ALMA,” he added.
ALMA, now under construction at an elevation of 16,500 feet in the Atacama Desert of northern Chile, will provide astronomers with the world’s most advanced tool for exploring the universe at millimeter and submillimeter wavelengths. ALMA 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 the first stars and galaxies that formed in the early universe, to learn long-sought details about how stars are formed, and will trace the motion of gas and dust as it whirls toward the surface of newly-formed stars and planets.
“This was fantastic work. Using our two prototype antennae to observe Saturn was the first complete, end-to-end test of the advanced systems we are building for ALMA,” says Adrian Russell, North American Project Manager for ALMA. “ALMA is an extraordinary international endeavor, and the collaboration of partners from around the world is vital to the success of the project.”
“The success of this test is fundamental proof that the hardware and software now under development for ALMA will work to produce a truly revolutionary astronomical tool,” says Massimo Tarenghi, Director of the Joint ALMA Office.
“This achievement results from the integration of many state-of-the-art components from Europe and North America and bodes well for the success of ALMA in Chile,” said Catherine Cesarsky, ESO’s Director General.
In addition to the leading-edge electronic and electro-optical hardware and custom software that proved itself by producing ALMA’s first fringes, the system’s antennae are among the most advanced in the world. The stringent requirements for the antennae included extremely precise reflecting surfaces, highly accurate ability to point at desired locations in the sky, and the ability to operate reliably in the harsh, high-altitude environment of the ALMA site.