ALMA Matters

From/de Gerald Schieven
(Cassiopeia – Autumn/l’automne 2016)

Cycle 4 Observing Begins October 1

Since the last issue of this newsletter, the results for the Cycle 4 call for proposals were released. Of the 1571 submitted proposals, 31 had PIs from Canadian institutions, and 153 had some Canadian participation. Of these, 9 proposals with Canadian PIs were awarded time (grade A, B or C) requesting 92 hours, or 5.2% of the time allocated to the North American queue. Cycle 4 observations will begin October 1.

Two Canadian ALMA Development Studies Funded

To maintain ALMA on the forefront of science in the long term, the ALMA Observatory through its Regional Centers provides funding to explore and develop new ideas, techniques, and technology that may have substantial impact on the science capabilities of the facility. Recently six North American projects were granted Development Study funding, among them two projects led by Canadians. The full list of projects can be viewed in the August NRAO e-News. NRAO expects to issue a new Call for Proposals for Development Projects on 10 October 2016. Please see the September NRAO e-News for further information. The deadline for proposals will be at the end of January 2017.

“Cleaning Up Interactive Cleaning” (Rosolowsky (UAlberta), & Kern (NRAO))

The ALMA Development Program is supporting a Study in “Cleaning up Interactive Cleaning” for the CASA software package, led by Erik Rosolowsky (U. Alberta). In many cases, the results from ALMA imaging can be significantly improved by defining regions which contain emission in the deconvolution process. This project will develop a new GUI tool to manage supervised deconvolution, which will enable it to be used in large ALMA data sets. The tool will be built in the new CARTA image viewer, allowing the new viewer to have the same set of functionality as the current CASA viewer.

“Prototype of a Complete Dual-Linear 2SB Block and a Single-Polarization Balanced 2SB Block” (Henke, Naranjanan, & Knee (NRC-HAA))

As part of the Cycle 4 ALMA Development study, we will explore the feasibility of integrating the OMT into the sideband-separating (2SB) waveguide block. We propose to machine and test two prototypes: (1) a dual-linear polarization 2SB block assembly, and, (2) a single polarization balanced 2SB block assembly. Prototype #1 will be used to explore possible improvements in image rejection, narrowband noise temperature, and integration. Prototype #2 will extend the results further to evaluate the added advantages of a balanced receiver, namely reduced signal reflections and LO sideband noise. Measurements will be completed using a spare ALMA Band 3 receiver cartridge and test set currently available at NRC Herzberg. Each prototype piece uses a turnstile as the first element which integrates the OMT into the block and provides the initial power division required for sideband separation. We intend to explore hole couplers as an alternative to branch-guide couplers which are used in most ALMA receiver cartridges. Broad-wall hole couplers are very high quality couplers that are broadband and exhibit high directivity.

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