With the acceptance of ALMA production antennas in Chile now underway, further system verification tests will occur on the full production system, initially at the Operations Support Facility (OSF) and then at the 16,570 foot elevation Array Operations Site (AOS). The first quadrant of the ALMA correlator is now operating in the AOS Technical Building.
The AOS site has been extensively reworked. Roads are being built to numerous antenna locations and dozens of foundations have received concrete. Hundreds of workers, contractors, and ALMA employees are making steady and significant progress on everything from heavy construction to the tuning and testing of the array’s cutting-edge electronics.
Antenna production lines continue their steady shipments to Chile. Thirteen ALMA antennas are now on-site and more will arrive in the near future. Both massive transporters traverse the site and have moved several antennas as new ones arrived. The first receiver and backend packages have been installed in the accepted antenna and have passed their initial tests. The post-construction operational phases of ALMA have been built up throughout 2008, and operations has taken over the day-to-day running of completed ALMA facilities.
2009 promises to be a very productive year as the fruits of ALMA production lines around the world are delivered to the site for assembly, integration, verification and commissioning. By the end of the year, the AOS infrastructure will have been readied and fully equipped antennas will produce the first glimpses of the transformational science ALMA is expected to produce.
Throughout its lifetime, the ALMA Test Facility (ATF) in New Mexico demonstrated the operation of the system now poised for science commissioning in Chile. With its mission complete, the ATF closed on 20 December. The procedures for testing antennas were developed at the ATF following the arrival of the first prototype antenna in May 2002. A system was then built around the two prototype antennas, leading to successful astronomical validation of the system over the past few months.
On 18 December 2008, the first ALMA production antenna was accepted by the project, having passed its acceptance tests. The antenna was produced by the Mitsubishi Electric Company (Melco) under contract to the National Astronomical Observatory of Japan, and was moved by the transporter on 8 January 2009 to a foundation at the Operations Support Facility (OSF) for further testing. At the end of January a series of holography measurements, panel adjustments, and pointing tests will occur. After that, total power astronomical validation tests will begin, using the production Front End and Back End installed last year.
Meanwhile, acceptance tests will be completed for a second antenna, produced by VertexRSI under contract with Associated Universities Inc. It will be equipped with the Front End recently delivered from the East Asian Front End Integration Center in Taiwan, and it will follow a similar set of testing procedures.
The remaining three Melco and eight Vertex antennas on the site will follow. Parts for the first antenna produced by AEM under contract with ESO have also arrived at the OSF and these antennas will join the growing antenna family during the year.
At the AOS antenna foundation construction continues. The first 12m antennas will occupy foundations within the Atacama Compact Array (ACA) area, for which the power and fiber optic cable infrastructure construction are more straightforward than in the larger Compact Array cluster. Fiber optics bring the antenna signals to the correlator at the AOS Technical Building where the fiber optic patch panel was recently completed. These steps lead to astronomical validation of the fledgling ALMA array expected later this year.
A Review of the ALMA Project was held 9-11 December 2008 in San Pedro de Atacama, Chile with visits by the panel to the OSF and AOS sites. The Review was commissioned by the ALMA Board to inform the Board and funding agencies as to the status of the Project, including management, progress, schedule, budget performance, current issues and risks for ALMA construction and operations. At the review, members of the Joint ALMA Observatory, Integrated Project Team (IPT) leads, and other key personnel outlined the progress since the last Review, with emphasis on items of concern at that Review. Many of the accomplishments described above were highlighted. Additional accomplishments included strengthening of the management structure and the establishment of schedule control mechanisms as production lines ramp up.
ALMA’s increase of two orders of magnitude in sensitivity and resolution, coupled with its prowess at imaging on all spatial scales, promises transformational science. Figure 6 is an image of the Vega debris disk as observed with the IRAM interferometer by Wilner et al (2002). From this image, and images made with the VLA and JCMT, Wyatt constructed a model of the disk structure. Using this model with the CASA simulator almasimmos, along with specifications for thermal and atmospheric noise, Reid constructed the simulated ALMA observation on the right.
Many of the structures hypothesized by Wyatt should be observed by ALMA. Most exciting among these perhaps is the rotation of the debris disk, observed as a migration of the material accumulated at points in the disk in resonance with an unseen planet, denoted by a cross in the Wyatt model. Note that Vega itself appears. As it is relatively bright and unresolved, it offers the possibility of self calibration of the image though that was not simulated in this instance. Vega is near the northern limit of ALMA imaging at a declination of 38 degrees.