ALMA Update

1 Recent news

A major focus of activity in the international ALMA project over the past few months has been the rebaselining of the project to bring it up to date since the definition of its schedule and budget in October 2002. There is the potential that this process will significantly impact project schedule and scope, but the project is determined to make every effort to avoid significant impacts on ALMA's Level 1 Science Requirements. In the United States, President Bush has signed an appropriations act that, among many other things, will fund NSF construction efforts for ALMA this year at the expected level of US$ 50M.

Adrian Russell, formerly head of the UK Astronomy Technology Centre in Edinburgh, has taken up his position as North American ALMA Project Manager at NRAO in Charlottesville.

Procurement of the antennas has been delayed from last year to this year as the bilateral partners (USA and Europe) work extremely carefully and hard to ensure the success of this critically important element of the construction project. Towards this end, testing has resumed at the Socorro Antenna Test Facility on the two prototype antennas. Designed to address remaining technical issues, these tests include 100,000 cycle (10 seconds per cycle, 24 hours per day for two weeks) fast switching tests.

Other parts of the North American ALMA effort continue to progress well. The first pre-production receiver cryostat was delivered from the UK. This one metre wide cryostat is designed to hold as many as ten receiver cartridges per antenna. Preliminary tests indicate the cryostat has considerable spare cooling capacity over its specification. The first Band 3 (at HIA) and Band 6 (at NRAO) cartridges are both performing well in their initial series of tests, and the back end and correlator work continues to make excellent progress (the latter under budget and ahead of schedule). The other two initial receiver bands for ALMA, Bands 7 and 9, are proceeding in Europe, and Japan is ramping up work on the Band 4, 8, and 10 cartridges (and on its Atacama Compact Array).

Work is continuing on the Operations Plan, with the first complete draft planned to be presented to the Board at their April 2005 meeting. Funding for ALMA operations has already begun to ramp up at NRAO and ESO through both new hiring and re-assignment of people to the ALMA project. A major task here in Canada in the next year will be to identify the specific contributions that we can make to ALMA operations.

In Chile, the interim offices of the Joint ALMA Office (JAO) in Santiago were opened in November. Mass excavation works at the Operations Support Facility (OSF) below Llano Chajnantor continue, as do road works.

In the area of outreach, there will be an ALMA lunch session at CASCA in Montréal in May as well as two posters describing the current Canadian work in receivers and software, and also a poster providing an update on the ALMA project as a whole.

2 ALMA Science Advisory Committee

The ALMA Science Advisory Committee met September 27-28, 2004 in Charlottesville, Virginia. The main focus of the meeting was on five charges from the ALMA Board. Unfortunately the report from the meeting is not yet on the public ALMA web page, but I hope it will appear there soon. I will summarize the main points here.

Most of the discussion focused on the first charge, which was to recommend science-based criteria that could be used by the project in preparing tradeoff studies should the budgetary situation require them. This discussion was particularly difficult because the ASAC was not given any financial information as to what the cost savings of a particular change to ALMA might be. The ASAC concluded that the loss or reduction of any element of the baseline project will result in significant loss of ALMA science. One interesting point is that imaging simulations presented at the meeting suggest that the effect on image quality of decreasing the number of antennas in ALMA is incremental, in a similar way that reducing the number of antennas by one would result in a slight increase in the rms noise level achieved in a given integration time.

We also had an extensive discussion on the second charge on how to facilitate joint projects between scientists from the different ALMA partners, large proposals, and legacy projects. Based on those discussions, the ASAC felt that the best way to handle large programs would be to have a single International Program Review Committee (similar to the ITACs for the JCMT and Gemini) that would rank and/or choose between large proposals. Scientific overlap between small proposals was felt to be a less critical issue, as smaller amounts of ALMA resources would be at stake. I recommend that anyone interested in these issues read the report when it becomes available. However, it is important to bear in mind that working out time allocation for ALMA is an on-going process and our thinking on it may well evolve with time.

On the charge related to calibration, the ASAC concluded that relaxing the absolute amplitude calibration specification from 1 to 3% below 300 GHz and from 3 to 5% above would not have a prohibiting impact on ALMA's major science goals. However, we emphasized that repeatability and relative accuracy should be maintained at a higher level. On the charge related to demonstration science and community involvement, the ASAC thought this would be best achieved by teaming astronomers from the wider community with ALMA experts to execute projects end-to-end, from the definition of scheduling blocks through observations and data reduction to publication. On the current draft science verification plan, the ASAC was concerned about whether sufficient scientific staff would be available to carry out the plan, as well as the short time currently allocated for science verification.

The ASAC met again February 24-25, 2005 in Garching, Germany. We had only two charges from the Board for this meeting. The first charge asked us examine the status of ALMA re-baselining and to comment on the scientific impact of any proposed changes. The second charge was a repeat of the charge from our previous meeting regarding facilitating joint projects etc. Since the ASAC report is not yet finalized as I write this, I will summarize our conclusions in my next report and at the ALMA lunch meeting at CASCA.

3 ALMA Developments in Canada

3.1 Band 3 Receiver Development

As noted above, the Band 3 Receiver Project at HIA continues apace. Cartridge #1 is scheduled to be delivered to the NA Integration Centre this spring. The Cartridge Test Set has been equipped to perform all the tests required for checking the specifications. Each of these experiments needed to be completely established before full characterization could begin. To accomplish these tests for each LO frequency (every 1 GHz), a tuning table needed to be generated that would be valid over the mixer operating range of 3.75 to 4.25K. Also, since the cartridge must be tested within the appropriate environment, extremely careful setup is required. The HIA Test cryostat thermal stability and temperature must be identical to the Front End one. The Cartridge Test Set is now running in semi-automated mode and will be upgraded to be fully automated by the end of this year.

Initial measurements of Cartridge #1 reveal that it should have no problem meeting the specifications. The Band 3 receiver has unprecedented performance characteristics. The single sideband noise is an impressive 40 K. Image rejection is better than -10 dB. Gain saturation is better than 5%. Gain stability, on timescales 0.1 to 1 sec, is less than 4×10^-7 (Allan variance). Cross-polarization is better than 20 dB. The IF output power and signal flatness also meet specifications, i.e. 4 dB peak to peak in any 2 GHz and 6 dB peak to peak across the whole IF band (4-8GHz). The excellent test results for Cartridge #1 are a testament to the entire Band 3 instrumentation team.

Keith Yeung has returned to the Band 3 Project (welcome back!) and is playing an instrumental role in the commercialization of the Band 3 IF amplifiers. A 4-8 GHz cryogenic high electron mobility transistor (HEMT) amplifier has been developed at HIA specifically for the ALMA Band 3 receivers. This low noise amplifier (LNA) is designed to amplify the IF signal at a cryogenic temperature of 4 Kelvin by more than 30 dB and has an ultra low noise figure of less than 5 Kelvin. A contract was let to Nanowave Technologies Inc. of Toronto last October to manufacture forty-three copies of these HIA amplifiers for the eight Band 3 preproduction cartridges. HIA is currently negotiating a technology license agreement for Nanowave Technologies to supply all the remaining LNAs for the Band 3 production cartridges and, possibly, for the Band 4 and 8 cartridges being developed by the ALMA-Japan Teams.

For more information on the ALMA Band 3 Receiver Project contact Doug Johnstone (Project Scientist - doug.johnstone@nrc-cnrc.gc.ca), Stephane Claude (Project Engineer - stephane.claude@nrc-cnrc.gc.ca), or Keith Yeung (Project Manager - keith.yeung@nrc-cnrc.gc.ca).

3.2 Software

The January 2003 audit of the AIPS++ package for ALMA offline data processing concluded that support for the recording of the data processing history was inadequate. This was marked as a high-priority defect within the package and as a result, Raymond Rusk and Gary Li have been heavily involved in the effort to improve this.

After Raymond and Gary completed integrating Juan R. Pardo's atmospheric model into AIPS++, they moved on to logging important AIPS++ data processing steps to the history section of AIPS++ data tables including:

flagging measurements suitable for scientific use
calibrating data against known astronomical sources
imaging observations

While Gary worked primarily on recording the flagged data, Raymond did all other work related to this task and also added code to make this information retrievable in an easy-to-use format.

Shortly after completing his flagging work, Gary was assigned the important task of fixing the slow filling problem of almatifiller, a tool used convert to and from ALMA and AIPS++ data formats for Plateau de Bure Interferometer (PBI) observations. He then proceeded to work on adding tolerance to the frequency and pointing models so that frequencies within the given tolerance will be indicated by identical spectral window IDs. This enhancement is especially useful to the vlafiller tool.

David Fugate has been heavily involved in an effort to clean up existing ALMA Common Software (ACS) to conform to ALMA Software Engineering coding standards. While most ACS code predates the standards, it is vital to adhere to the standards for maintenance reasons. As always, a substantial portion of his time has been used to support ALMA software engineers throughout the world which includes investigating ALMA software problem reports. Recently David has contributed much to the ACS 4.1 design discussions and has just been assigned his tasks for ACS 4.1. This consists mainly of improving and adding to ACS documentation in addition to a complete refactoring of the ACS logging mechanism to permit its reuse within the ALMA Offline software subsystem (i.e., AIPS++).

Chris Wilson is currently carrying out the third test of the ALMA Pipeline software, which is a regression test to see if needed changes identified in the November 2004 test have been implemented adequately. The next pipeline software test will likely take place in early summer 2005 and will again involve outside testers. Anyone interested in participating in this test (and getting an early peak at ALMA Pipeline processing) should contact Chris.

3.3 Other related news

The 10 micron water vapour monitor (IRMA) concluded testing on the Submillimeter Array in early January, 2005, with two of the three units having demonstrated a continuous run without failure of over 4 months. The third unit was brought back to Lethbridge in late November in order to be upgraded for deployment at Gemini South. This was done in February where Gemini are evaluating its use as an observing scheduling aid. In order to make more progress with data analysis, the IRMA project will have a PhD student added to it within the next couple of months.

Chris Wilson wilson@physics.mcmaster.ca

Canadian ALMA Project Scientist

(with input from Jim Hesser, Doug Johnstone, Lewis Knee, Robin Phillips, and Russ Taylor)

File translated from T_EX by T_TH, version 3.40.
On 18 Jun 2005, 12:39.