ALMA Update

By Gerald Schieven and Douglas Scott

(Cassiopeia – Spring 2015)

Call for Proposals (Cycle 3)

On March 24, the Joint ALMA Observatory will issue a call for proposals to observe in Cycle 3, to run from 1 October 2015 through September 2016. The deadline for proposal submission will be 15:00 UT on 23 April 2015. Information will be found on the ALMA Science Portal at ALMA Science.

The Millimetre Astronomy Group at NRC Herzberg acts as a node of the North American ALMA Research Center, in support of ALMA operations and for the Canadian community. Please contact Gerald Schieven, Brenda Matthews or James Di Francesco if you need assistance with ALMA proposal preparation and/or data reduction.

Douglas Scott is the Canadian representative on the North American and international ALMA Science Advisory Committees, and should be contacted for information related to these committees, or to ensure that issues of specific interest to Canadians are discussed at future meetings.

Science Verification Data Sets from the Long Baseline Campaign

New data sets have been released, including long baselines for the first time. These are scientifically interesting in their own right, as well as being useful for demonstrating the future capabilities of ALMA. The targets are the HL Tau circumstellar disk, the z=3 lensed galaxy SDP.81 and the asteroid 3 Juno. The basic observations are described in 3 papers (plus a 4th overview paper) that have been accepted for publication in ApJL. These join the approximately 200 papers that have already been published based on ALMA data.

New Call for Development Studies

A new Call for Development Studies is being issued on 2015 March 16. The primary aims of these studies are to:

  • give groups in North America the opportunity to propose ALMA upgrades that may later be implemented as part of the ALMA Development Plan;
  • support the development of conceptual and detailed designs for ALMA upgrades; and
  • encourage relevant long-term research and development in areas important for ALMA.

The completed studies will be used, together with similar studies from the other ALMA partners, to augment and implement the ALMA Development Plan. The period of performance for funded Studies will run from the award date (October 1, 2015) to no later than September 30, 2016 (approximately one year). Award pool – a total of one million U.S. dollars ($1.0M) is available for funding Studies during the FY2016 Development Program cycle (subject to the FY2016 Federal Budget and allocation of funds). As a guideline, the NRAO expects to fund several Studies. No individual Study will be funded in excess of two hundred thousand U.S. dollars ($200K). Proposers are requested to submit a Notice of Intent by May 15, 2015. The closing date is June 12, 2015. (A call for Development Projects, for which the aim is to implement the results of a Study, is expected in 2016.)

Further details are can be found in the “Conditions Governing the Call for Study Proposals” (available at
Call for Proposals Study; refer to the “Proposal Documents” table).

In the previous call for development studies issued in 2013, two of the six funded projects had strong Canadian participation. One of those is described below.

Heterodyne Receiver Array Development Study

NRC Herzberg participated in the first round of NA Development Studies, analyzing the need and conceptual optical design for a heterodyne receiver array for the ALMA 12-m Total Power Array antennas. Such an instrument could greatly improve the efficiency of recovering single-dish data that are combined with mosaics of single pointings obtained with the interferometric ALMA 12-m Array. The study was conducted by Stéphane Claude, Doug Henke, and James Di Francesco. Since typical heterodyne arrays have on-sky beam spacings of ~2 x FWHM, they are somewhat inefficient at gathering single-dish data for mosaics. Instead, an array with a much more closely-packed architecture could sample the relatively small areal sizes of interferometric mosaics more efficiently. Such a close-packed design, incorporating a cold stop within the optical path, was investigated as part of the study. First, a fully sampled hexagonally arranged array was considered and it was found that performance suffered from a very large increase in receiver noise due to the power terminated within the cold baffling of the cryostat. Next, it was shown that promising performance could be obtained if the spacing was increased to “twice-Nyquist” (still very compact for heterodyne arrays, since the packing density is increased by a factor of four). Performance depends on the frequency band chosen and the dominance of sky and background noise within the system. Further investigation of the dense heterodyne array (DHA) concept will continue, and a report detailing the results of the study will be submitted to NRAO mid-March.

ALMA Technical Maintenance

The Millimetre Technology Group (MTG) at NRC Herzberg in Victoria supports maintenance and repair of the ALMA Band 3 cold cartridge assemblies, which provide the 84 to 116 GHz frequency coverage of ALMA. These cartridges have proven to be very robust, with only 3 cartridges per year (of a total complement of 72) returning to NRC for repair. In January-February 2015 NRC Herzberg staff travelled to the OSF in Chile in order to install and commission a second cartridge test set system (CTS-2; CTS-1 is in the laboratory in Victoria), which is an integrated system for testing, troubleshooting, and verifying Band 3 receivers. The presence of CTS-2 in Chile, with ALMA staff trained by NRC, will permit some of the more routine repair and maintenance tasks to be done at ALMA, minimizing transport of cartridges between Canada and Chile. It will also facilitate ongoing Band 3 upgrade activities.

ALMA Band 3 Development Project

In addition to the Development Study described above, the MTG is currently involved in an ALMA Development Project, to enhance the stability of the Band 3 cartridges by upgrading them with permanent magnets and deflux heaters. A few cartridges have been upgraded with magnets and tested in the field on antennas at ALMA, and results look generally promising. The second thread in this effort is the design, implementation, and testing of the deflux heater system. The upgrade of the Front End laboratory at the OSF with CTS-2 will greatly facilitate the upgrading process (the current plan is for NRC to provide a “parts kit” for each cartridge to be upgraded in Chile).

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