ALMA Update

1  Recent news

1.1  First Fringes at the OSF

A major effort within the ALMA project is focused on achieving phase closure with three antennas on the high site at 5000 m by the end of the calendar year. This is an important milestone for the ALMA project. In preparation, a series of tests of the individual antennas are being carried out at the Operations Support Facility (OSF). Tests carried out so far include the absolute all sky pointing, offset pointing, and surface accuracy. Tests to measure the details of the shape of the beam and the antenna efficiencies are just beginning.
In addition, tests of the performance of the entire system, including interferometry between two antennas, are being carried out at the OSF. The two antennas that have been tested in single dish mode over the past few months were first pointed at the holography beacon to obtain static fringes in early April. On April 30, both antennas were pointed at Mars and static fringes were observed, thus validating the radiometric pointing models and the focus for the antennas. "Static fringes" means that software was not used to control or follow changes in the fringes as the source follows its diurnal path through the sky.

The next interferometric test used updated ALMA software to control all aspects of the observation, e.g., geometric delay of the signal paths between the two antennas. "Dynamic" fringes were obtained on June 12, for which computations are continually updated to drive the electronics and track the changes in the fringes as the source treks on its daily route across the sky. In this case, the spectral lines from the silicon monoxide (SiO) maser in the heart of the Orion Molecular Cloud were observed at 86 GHz. These observations used the Band 3 receivers built by the Herzberg Institute of Astrophysics as part of Canada's contribution to ALMA construction.

 

  
Figure 1: The first dynamic fringes obtained with two ALMA production antennas observing the Orion Molecular Cloud from the OSF. The single antenna spectra are shown in the upper two panels, with the spectrum and phase between the two antennas shown in the lower two panels. Image from ALMA Science IPT wiki (June 2009).
  

1.2  Other Construction Progress

ALMA accepted its third antenna, the second production antenna designed and built by Vertex, on April 29, 2009. This antenna has been equipped with the Front End recently delivered from the European Front End Integration Center at Rutherford Appleton Labs. This acceptance allowed completed Vertex antenna No 6 to be moved to an outside location for eventual sky testing. Its brethren No 3 and No 5 are also outside the building for testing. Three Melco antennas have completed construction and are awaiting acceptance tests. All parts for the first antenna designed and built by Alcatel under contract with the European side of ALMA are now in Chile and assembly of the antenna is underway. In total, there are 14 antennas in various stages of construction and testing at the OSF as well as portions of various other antennas.

Construction continues at the high site (the Array Operations Site, AOS). Concrete has been laid for 132 foundations so far. The 22 foundations required for the Atacama Compact Array (ACA) have all been finished and provisionally accepted; 66 additional foundations have also been provisionally accepted. Electrical, fiber, and road connections will be put in place over the next few months. The second quadrant of the correlator is being prepared for shipping from NRAO; physical installation in the AOS technical building is expected in August.
Two Water Vapour Radiometers (WVRs) have passed their provisional acceptance on-site. The first WVR achieved first light in the Vertex antenna but has since been moved to the AIV lab for further testing. WVRs are a critical system to allow ALMA to achieve its full potential in angular resolution and sensitivity, particularly at high frequency. The two Laser Synthesizers built by Teraxion where shipped to Charlottesville in April.
Figure 2: The third ALMA production antenna being moved by the ALMA transporter. The antenna in the foreground is the next antenna in the testing queue.
 
The Call for Tender for power supplied by an overhead transmission line from Calama has been declared failed. An island mode liquid gas generator system similar to that used at the VLT is the currently favored design.
If my quarterly ALMA updates are not frequent enough for you, a good source for monthly updates on the ALMA project is the new electronic NRAO newsletter http://www.nrao.edu/news/newsletters/
And don't forget the ALMA observatory web site
http://www.almaobservatory.org which contains wide range of information about the observatory, including details about science and technology, infrastructure, geographical location, etc. From there, you can also check out and subscribe to the new ALMA electronic newsletter (go to Newsroom and click on Newsletter), which comes out every few months and contains longer articles on various aspects of ALMA as well as recent updates.

1.3  Canadians involved in ALMA

This section will be an intermittent part of my updates focusing on Canadians who are involved in ALMA construction. I received this interesting email in June from Jean Francis Cliche.
I just want to give you the latest ALMA news from another Canadian. You may remember I worked for TeraXion and developed the Master Laser and Laser Synthesizer for the Central LO. I now work as a consultant for the NRAO Back-End group, and I live in San Pedro de Atacama with my wife Emma and 2-year-old daughter. Emma is a researcher at Concordia University in Montreal and is doing a survey of plants and butterflies on Chajnantor for ALMA.
Last February, Back-end and I have successfully delivered, installed and tested the tCLOTS to the OSF (temporary Central LO test Stand). This system allowed two antennas to receive the first LO, and allowed first fringes to be observed at the OSF. There are plans to build another equivalent of tCLOTS to allow simultaneous total-power tests of more antennas. As you know, antennas are piling up here faster that they can be processed. That's normal at this stage and AIV is working through them systematically.
I'm currently working on documenting the test plan and procedures, and analyzing and documenting the test results of the first CLO, which is in Charlottesville and will be shipped to the AOS by the end of June.
I'll be based in Montreal as of September 2009 (Emma' sabbatical will be over) but I will come to Chile regularly to continue to assist the commissioning of BE hardware. I hope we'll be able to come back live here soon, for it is a beautiful place.

2  ALMA Meetings

2.1  Preparing for ALMA: from Science to Observations

The first Canadian ALMA workshop was held June 1-3, 2009 at McMaster University. This was a hands-on workshop for Canadian faculty, postdocs and students interested in learning about how to use ALMA. Funding for student local expenses was provided by the University of Calgary through the Canadian Foundation for Innovation grant for ALMA construction and software and funding for the speakers was provided by the Herzberg Institute for Astrophysics. We are very grateful for their support of the workshop.
The workshop was attended by 55 people, mostly graduate students but with a good involvement by postdocs and faculty as well. The first day included lectures on the basics of radio astronomy and interferometry, while the second day consisted of lectures and demonstrations of the CASA data reduction software and its simulation capabilities, as well as shorter presentations on the ALMA Observing Tool and the SPLATALOGUE spectral line database. The third day was an unstructured, hands-on day where participants could use the CASA software with advice and guidance from the experienced speakers and participants.
The presentations and scripts used can be downloaded from the conference website, 
http://www.almatelescope.ca/Workshop/Schedule.html
Links to the software discussed can also be found at the website.
We received very positive feedback from the workshop participants. They found the lectures very useful and particularly appreciated the hands-on work with CASA on the third day. Overall I feel that the workshop was very successful and I hope to be able to hold a similar workshop in a few years when ALMA is operational. In the meantime, the next step is to hold a shorter half-day meeting to inform the community about Early Science opportunities with ALMA. This meeting will be held in conjunction with the 2010 CASCA annual meeting at Saint Mary's University in Halifax.

2.2  Upcoming ALMA Science Meetings

The next NRAO workshop on "Assembly, Gas Content, and Star Formation History of Galaxies", will be held 21-24 September 2009 in Charlottesville, Virginia.
In the last two decades, the availability of large ground-based and space-based facilities, and improved theoretical modeling, have led to significant advances in our understanding of star formation, the gas cycle in galaxies, and galaxy assembly and evolution over cosmic time. With the next generation of long-wavelength ground- and space-based facilities set to become fully operational in the first half of the coming decade, the time is ripe to review the theoretical and observational progress that has been made in the areas of extragalactic star formation, interstellar gas properties and galaxy assembly, and to assess where science with facilities such as ALMA, EVLA, Herschel Space Telescope, and the JWST are likely to contribute transformational understanding in these areas.
Keys issues to be addressed are:
A major goal of this meeting is to highlight the capabilities of ALMA, and its synergy with the EVLA, Herschel, JWST, etc., in driving transformational science in these key areas in the next decade. The web site for the meeting is 
http://www.nrao.edu/meetings/galaxies09/
The next ESO-MPE-MPA-USM Joint Workshop, "From circumstellar disks to planetary systems", will be held November 3-6, 2009 in Garching, Germany. The goals of the workshop will be to review the status of the field and to discuss transformational programs that will be made possible with the upcoming facilities, and especially by the combined use of the ESO present and future facilities. To achieve this, the workshop will bring together the communities working with ground based infrared large telescopes and interferometers, with space observatories and millimeter interferometers as well as theorists. The web site for the meeting is 
http://www.eso.org/sci/meetings/disks2009/index.html

3  ALMA Developments in Canada

3.1  Band 3 Receivers and Development

The Band 3 production is progressing very well. Currently we have completed 19 Band 3 cartridges. With the excellent yield of the recent T3-268 SIS wafer, we are able to build up a healthy inventory of 2SB mixer subassemblies for up to Cartridge #34. RAL has been able to catch up with the production backlog of the Band 3 cartridge bodies; a new batch of 10 cartridge bodies was delivered to HIA at the beginning of June. We have thus been able to use them to build up an inventory of 4 fully assembled cartridges awaiting RF testing. All in all, we are currently running about a month ahead of the delivery schedule given to the ALMA project.
HIA has started development work on the Band 1 receiver. A collaboration has started between HIA, ASIAA in Taiwan and The University of Chile. At HIA, systems and component design has started and some results were presented at the Millimetre and Submillimetre Astronomy at High Angular Resolution conference in Taipei, June 8-12. The optics and the Low Noise Amplifier (LNA) are currently the main contributors to the systems noise and lots of effort is being devoted to these sub-systems. HIA and U of Chile are collaborating on finding an optimum optics design. At HIA, we are testing cryogenic LNAs with a goal of meeting the gain and noise specification. Recently a prototype Orthomode Transducer specifically designed to fit within the Band 1 volume envelope was test at HIA and showed exceptional performances. Systems analysis, such as noise, gain, local oscillator design and optics alignment, is currently underway at HIA.

3.2  Software

The soon to be released version of CASA, beta 2.4.0, was used at the Canadian ALMA workshop and performed well. Keep your eyes open for the new release at NRAO's website coming sometime in the next week or so.
At the University of Calgary, the lone Canadian CASA developer, Shannon Jaeger, has continued to contributing to the image analysis portion of CASA. This includes maintaining/enhancing the CASAcore code to the Python tasks and providing test suites. The latest addition is a task for performing smoothing; currently two types of kernels (gaussian and boxcar) are supported, and there are plans to add more. Other tasks included looking into issues with the lack of precision in regridding, creating and using regions in an image, and general support of the image analysis portion of CASA. The scope of Shannon's responsibilities for CASA is shrinking in preparation for her departure from the project as the funds for the construction phase of ALMA are nearing their end.
In work on ALMA Common Software, Arne Grimstrup continues to develop the Python package for converting the ALMA Project Data Model for use with Python components. His package has successfully processed data for Observing Proposals, Observation Projects and Scheduling Blocks generated by the ALMA Observing Tool. A preview demonstration of the conversion package was also made to members of the ALMA CONTROL software team was made in late May. Reaction to the new tool was positive and many ideas for additional features were discussed. Jorge Avarias joined the ACS team at the beginning of May, so Arne is mentoring our newest colleague.
At McMaster University, Chris Wilson completed the second round of regression tests for the ALMA Pipeline subsystem focusing on reducing single field interferometric data. She also completed a regression test on the capabilities for reducing single dish data, which will be needed for ALMA observations of extended sources. The Pipeline team is currently preparing for the next User Test which will focus on improvements to the calibration algorithms for single field interferometry and also the first implementation of mosaics with interferometric data. This User Test is currently anticipated to start in July.
Chris Wilson wilson@physics.mcmaster.ca
Canadian ALMA Project Scientist
(with input from Jean Francis Cliche, Shannon Jaeger, and Gerald Schieven, as well as material from Al Wootten and the NRAO and ALMA newsletters)


File translated from TEX by TTH, version 3.40.
On 23 Jun 2009, 11:10.