Figure 1: Three ALMA antennas await commissioning at the 5000m Array Operations Site in northern Chile. Image courtesy ALMA (ESO/NAOJ/NRAO), W. Garnier (JAO)
Figure 1: Three ALMA antennas await commissioning at the 5000m Array Operations Site in northern Chile. Image courtesy ALMA (ESO/NAOJ/NRAO), W. Garnier (JAO)
As 2009 drew to a close, the Atacama Large Millimeter/submillimeter Array (ALMA) passed a key milestone to cap a year that had begun with the first detection of radio waves by a single antenna. ALMA astronomers and engineers worked together to successfully link three antennas at the 5000m (16,500 ft) elevation Array Operations Site (AOS) in northern Chile. This first step on the path to the sensitive, precise, high-resolution imaging which will be an ALMA hallmark demonstrated the success of the full electronic and software system now being installed. The ALMA phase closure, as this test is called, came as part of an ongoing series of tests beginning in late November. It was a key step to the beginning of the formal commissioning period, which leads to Early Science and, of course, completion of the construction. "This successful test shows that we are well on the way to providing the clear, sharp ALMA images that will open a whole new window for observing the Universe. We look forward to imaging stars and planets as well as galaxies in their formation processes," said Fred Lo, NRAO Director.
At a recent review, it was decided that the commissioning period will begin on 2010 Jan 22, coincidentally one year from the establishment of ‘first light’ at the Operations Support Facility. This intense period will see the addition of the other antennas already on-site. Twenty-two antennas are in various stages of erection in northern Chile. Five of these antennas are already being used by ALMA; additional antennas await their turn in the queue. The two antennas at the lower-elevation Operations Support Facility will soon be linked together in a rebirth of the test interferometer there; testing of new software, antennas and other equipment normally will proceed on this instrument while commissioning tasks occupy the array at the AOS.
Recently, a software upgrade has been tested at the AOS array. This upgrade will enable many new capabilities, such as phase correction using the water vapor radiometers (WVRs) and broadband spectroscopy. In a test of ephemeris capabilities, the interferometer recently observed the four Galilean satellites of Jupiter. Appropriately enough, the date of this observation was exactly four hundred years after Galileo’s 11 Jan 1610 discovery of the these remarkable moons.