AUI News Release
ALMA at 5 Antennas
On 29 April Vertex antenna DV03 was moved to the Array Operations Site (AOS) at 16500 ft elevation, bringing the array there briefly to four antennas—one antenna was taken back down to the Operations Support Facility for upgrades, and the array fell back to three. In the third week of May it returned to the AOS to be placed on pad J504 and on the 20th of May amplitude closure was achieved on the four antenna array.
On 31 May Vertex antenna DV05 arrived on pad T701, a location eventually slated to support one of the Atacama Compact Array (ACA) 12m antennas.
Astronomers and engineers soon succeeded in linking all five antennas for commissioning activities. The ten baselines available between these antennas offer a marked improvement in ALMA's imaging ability; by Early Science about a year from now sixteen antennas will provide 120 baselines and enable scientists to explore the southern sky with unprecedented sensitivity and precision. The integration of the third quadrant of the 64-station correlator continues at the Array Operations Site Technical Building nearby the array. Tests of the ACA correlator from NAOJ are also proceeding at the AOS TB.
Meanwhile at the 2900m Operations Support Facility (OSF) another three antennas await their journey to high altitude. DV07 finished its holographic surface accuracy verification. Meanwhile, the NRAO Front End Integration Center in Charlottesville delivered a new Front End component, the first to contain six receiver cartridges. This unit provides capability at wavelengths of 2mm and .6mm by incorporating these cartridges, delivered to NRAO from NAOJ where they are manufactured. This Front End also passed through all of its test at the cadence required for the ALMA construction schedule.
During June, commissioning continues. One antenna is scheduled to be moved to longer baselines for tests best performed in that configuration. Another antenna will move back to the OSF for installation of some updated components. It is expected that more antennas will be accepted by ALMA from their contractor during the month, moving from the contractor facility to the OSF for system assembly, integration and verification there.
