ALMA Construction Continues

ALMA Image of Moon

Figure 1. (Left) An optical image of the Moon on Feb 27, 2008. (Right) An image at 147 GHz made with a Melco antenna.


ALMA Transporter

Figure 2. An ALMA transporter lifts a dummy load designed to mimic the mass of an antenna.


Antenna Station Excavation

Figure 3. Antenna station excavation has begun at the center of the array at the 16,400-foot level. The Array Operations Building is in the background; the newly completed transporter shelter is to its left.


ALMA Front End

Figure 4. The first ALMA Front End undergoes provisional acceptance at the OSF in May.  The sensitive detectors are in the large blue dewar, which keeps them temperature stable at near absolute zero.



Figure 5. Spectrum acquired with the prototype ALMA system at the ALMA Test Facility towards the Orion hot core.  Lines are labeled to identify the emitting species.


This quarter marks the tenth anniversary of the approval by the National Science Board of the ALMA Design and Development program, which led to the provisional acceptance of the first prototype antenna from VertexRSI in March 2003.  As of June, there are nine production ALMA antennas in Chile, including five production 12m antennas from VertexRSI and four from Mitsubishi Electric Co. (Melco).  Several of these antennas are undergoing tests that should lead to acceptance of the antennas from the contractors in the coming months.  Using a special receiver operating at 2 mm wavelength, a Melco antenna imaged the Moon in March (Figure 1).

The first accepted antenna will be tested at the 16,400 foot Array Operations Site (AOS) near the Technical Building toward the end of the southern hemisphere summer.  The antenna will be transported there by the massive transporters, which are concluding their tests and should be accepted by the project over the northern hemisphere summer.

The first ALMA production Front End has been delivered to Chile from the North American Front End Integration Center in Charlottesville.  This package contains electronics for collecting the faint signals from the sky. It will undergo provisional acceptance in Chile at the Operations Support Facility (OSF).  The Front End has now been integrated by the Assembly, Integration and Verification team at the OSF with the antenna-based part of the Back End, and the two-antenna correlation and system software, to produce a spectral density plot over a 2 GHz band for the first end-to-end test of these combined units. The members of the Front End IPT from Charlottesville at the site were: Christian Holmstedt, Andrea Vaccari, Denis Urbain, Morgan McLeod, Antonio Perfetto, and Kamaljet Saini.

At the ALMA Test Facility in New Mexico, the prototype system is routinely producing observations.  ALMA scheduling scripts direct observations, which are executed to produce data in typical fashion, including sequential observation of calibrator sources and targets.  Data are then transferred from the archive to the standard ALMA data format.  Data may then be inspected using the 'Quick Look' software, and imported into the CASA software for advanced processing.  An example of a calibrated spectrum of the Orion hot core is shown in Figure 5; the sensitivity approximates that of the Turner (1989) spectral survey of Orion.  For a more sensitive view of this portion of the spectrum, see the M. Guelin et al. article in the newly published volume Science with the Atacama Large Millimeter Array: A New Era for Astrophysics

Dr. A. Beasley has left ALMA to pursue other interests; Dr. Tetsuo Hasegawa assumed the duties of ALMA Project Manager in May.

Al Wootten