ALMA Matters

By / par Brenda Matthews and Gerald Schieven (NRC)
(Cassiopeia – Summer / été 2024)

WSU News

NRC Herzberg Astronomy & Astrophysics, along with colleagues from NRAO, are designing the new correlator for ALMA (the ATAC, or Advanced Technology ALMA Correlator), as part of a larger ALMA-wide effort to upgrade ALMA capabilities for the 2030s and beyond (the ALMA Wideband Sensitivity Upgrade, WSU). Last week, ATAC became the first of the subsystems to pass PDR (Preliminary Design Review), and so now enters Critical Design, and this excellent result will no doubt mark an important precedent for the whole WSU effort. At HAA, the ATAC team consists of Brent Carlson, Marty Cluff, Thushara Gunaratne, Stephen Harrison, Nitin Mehta, Michael Pleasance, Fan Zhang, with contributions from many others.

The PDR committee recognised the “Herculean effort” put in by the team, and described them as “phenomenally competent”, having created a “very elegant solution” for the design of the Correlator. Wow!

Cycle 10 Update

ALMA is currently in configuration C-5 (max baseline 1.4 km), moving outward to C-6 at the end of June, then moving inward to end the cycle in September in config C-3.

Cycle 11 Proposal Submission News

On April 24th at around 13 UTC, the day prior to the ALMA Cycle 11 CfP deadline, proposals requiring Bands 7 and higher started experiencing inconsistent observing time estimates. This was due to a temporary and intermittent connectivity issue between the online calibrator catalogue and the Observing Tool (OT), required to search for high frequency calibrators. When the calibrator catalogue could not be accessed, band-to-band calibration was assigned, resulting in an increase in the observing time estimates. In some cases, this prevented validation and submission if the observing time increased above the Large Program threshold. As announced on the Science Portal, initially the problem occurred intermittently and appeared resolved after a short time. Unfortunately, the issue recurred during the hours before the scheduled proposal submission deadline (April 25 at 15 UTC). A second issue related to user authentication also occurred close to the deadline, sometimes preventing users from logging in to submit their proposals. Both issues persisted until the deadline despite steps taken by ALMA to restart specific services. The issues were later identified as resulting from a performance degradation of the servers at the JAO, for which mitigating steps are being taken to prevent this occurring in the future.

To assist users who were impacted by these technical issues, ALMA took the following steps.

A second announcement was placed on the ALMA Science Portal instructing users to submit Helpdesk tickets prior to the ALMA deadline if they continued to be impacted by the issues. ALMA assisted all users who submitted Helpdesk tickets by the deadline and were unable to submit or resubmit their proposals due to these issues. Exceptionally, due to the issues occurring so close to the deadline, ALMA also helped users who submitted Helpdesk tickets immediately after the deadline. Observatory staff assisted users by submitting proposals (.aot files) to the ALMA Archive on behalf of these users. Only proposals affected by these specific issues were submitted in this manner.

All cases in which the proposal was submitted by the PI but with incorrect observing time estimates due to the calibrator catalogue issue will be fixed by the Observatory before proposals are sent to review. Reviewers will also be instructed to ignore any discrepancies in observing time estimates for Bands 7 and above.

It was decided to assist users in this way instead of extending the proposal submission deadline since the technical issues were ongoing and there was no estimate for when normal service could be restored.

Despite the problems affecting the final few hours of the Cycle 11 proposal deadline, ALMA has continued to have a strong demand for time on the telescope, with 1712 proposals submitted for Cycle 11, requesting 53533 hours of time on the 12m-, the 7m-, and the TP arrays. The number of proposals has remained steady over the last few cycles, while time requested for the 12m-array at 31,610 hours was the highest yet, with an oversubscription rate of 7.4. Canadian-led proposals are also continuing to be submitted in strong numbers with 51 proposals submitted requesting 2101 hours, an oversubscription rate of just over 10 of the Canada’s nominal share of North American time.

ALMA Primer Video Series

The ALMA Primer Instructional Video series, which can be found on the Science Portal here, is designed to provide a basic introduction to radio interferometry, calibration, imaging, and other topics in short (5-10 minute), easy-to-digest segments. As a work in progress, new videos are released periodically. A new video, an Introduction to Sidebands, Basebands and Spectral Windows, is expected to be released in early July, and several more will be released later this summer.

Other videos in the series include an Introduction to Radio Interferometry, Calibration, CLEAN, and much more. Subscribe to the ALMA Primer Video Series YouTube channel to be alerted to new videos as they are released.

We are always looking for ideas for new videos, and especially looking for people who would like to help with script generation, animation, and narration. If you have an idea or would like to join the Primer Video Working Group (at any level of effort), please contact

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