Overview

The ALMA proposal review process is organized by the Proposal Handling Team (PHT) at the Joint ALMA Observatory (JAO). ALMA proposals are selected by competitive peer review through either the distributed peer review process or the ALMA Proposal Review Committee (APRC).

Proposals that request less than 50 h on the 12-m Array or less than 150 h on the 7-m Array in standalone mode are reviewed using the distributed peer review system, in which the proposal team designates one member to participate in the review process. The outcomes of the distributed peer review process are:

• A scientifically ranked list of proposals
• Individual comments for each proposal written by the reviewers that are sent to the Principal Investigators (PIs).

Large Programs, i.e., proposals that request more than 50 h on the 12-m Array or more than 150 h on the 7-m Array in standalone mode, are reviewed by the APRC, a panel of experts selected from the international astronomical community. To ensure a thorough evaluation, external Science Assessors also provide reviews for Large Programs, which are considered by the APRC. The outcomes of the APRC review process are:

• A list of recommended Large Programs
• A consensus report for each Large Program that summarizes the strengths and weaknesses of the proposal.

All proposals are reviewed in a dual anonymous fashion in which the proposers do not know the identity of the reviewers and the reviewers do not know the identity of the proposers. All proposals need to be prepared in accordance with the dual-anonymous guidelines.

Distributed Peer Review Plenary Session

The PHT will host a series of Webinars to explain the distributed peer review process and answer questions. Slides and a recording of the presentation will be available on this website. Reviewers and mentors are strongly encouraged to attend one of the sessions or watch the recording at their convenience. The Webinars will take place between 7-11 May 2026, with times scheduled to accommodate participants across all ALMA regions. Reviewers and mentors are welcome to join the session that best suits their schedule. The schedule for the three sessions is as follows:

Session 1: Thursday May 7, 2026, 13:00 UTC

Session 2: Friday May 8, 2026, 2:00 UTC

Session 3: Tuesday May 11, 2026, 17:00 UTC 

Prior to the Webinars, the PHT will send an email to all reviewers and mentors with more detailed information.

Available Documents for the Proposal Review Process

 

Document	Description
Dual-anonymous Guidelines	Guidelines for PIs on preparing dual-anonymous proposals
Overview of Distributed Peer Review	Detailed description of the ALMA distributed peer review process
Guidelines for Reviewers	Instructions for reviewers on evaluating proposals and writing constructive comments for PIs
Reviewer Tool and User’s Manual	Access to the Reviewer Tool and its accompanying User’s Manual
Evaluation of Distributed Peer Review at ALMA	Summary of how distributed peer review compares with panel review at ALMA, based on analyses of proposal rankings, scientific diversity, and review quality.
Frequently Asked Questions	Answers to common questions about the dual-anonymous formatproposals and the distributed peer review process

 

New in Cycle 13

• The Guidelines for Reviewers have been updated to expand and clarify the description of high-, adequate-, and low-quality reviews, with additional characteristics and examples.
• An analysis of the outcomes of the distributed peer review process in Cycles 8-12 is under preparation, comparing results from distributed peer review and panel-based review, examining the scientific diversity of top-ranked proposals, and presenting findings from the Reviewer Comment Survey conducted in Cycle 12. A summary of the main findings will be posted in the Science Portal.

Proposal Review Timeline

This section summarizes the key milestones in the Cycle 13 distributed peer review and Large Programs review process. A brief description of each step is given below.

Table 1: Timeline of the Cycle 13 proposal review process

Date	Milestone
28 April 2026	Deadline for reviewers to provide their scientific expertise and their list of conflicts of interest before proposals are assigned.
06 May 2026	Proposals are released to reviewers. Stage 1 begins for both the distributed peer review and the APRC
13 May 2026	Deadline to provide conflicts of interest for assigned proposals
03 June 2026	Stage 1 deadline for all reviewers
04 June 2026	Distributed peer review Stage 2 begins
18 June 2026	Distributed peer review Stage 2 deadline
22 - 26 June 2026	APRC meeting
August 2026	Results sent to PIs

 

Distributed Peer Review

The distributed review process proceeds in two stages as described below. A complete description of the process can be found here.

Stage 1

The PHT will assign 10 proposals (a “Proposal Set”) to the reviewer on behalf of each proposal in which they are the designated reviewer.

The reviewers will rank the proposals within a Proposal Set from 1 (strongest) to 10 (weakest) and write a review for each proposal that indicates its strengths and weaknesses.

Stage 1 is mandatory. Reviewers must submit their reviews by the Stage 1 deadline (03 June 2026, 15:00 UTC) or the corresponding proposal for which they were identified as the designated reviewer may be disqualified.

Stage 2

Reviewers read the anonymized comments from the other reviewers and revise their own ranks and reviews as needed.

The deadline to complete Stage 2 is 18 June 2026, 15:00 UTC. If a reviewer does not submit the Stage 2 ranks and reviews, then the Stage 1 ranks and reviews will be considered final.

ALMA Proposal Review Committee

Large Programs are reviewed by the APRC. The general steps for the assessment of these proposals are outlined below.

Stage 1

The APRC members review their assigned proposals, provide a numerical score for the proposals, and write comments summarizing the strengths and weaknesses of the proposal. The PHT assigns each Large Program a Primary Assessor, who is responsible for leading the proposal discussion in Stage 2 and writing the consensus report that will be sent to the PI.

External Science Assessors review a small number (1-3) of Large Programs in their area of expertise and provide a written report with their reviews, which are provided to the APRC.

Stage 2

The APRC reads the reports of the external Science Assessors in preparation for the meeting. The APRC discusses the proposals and recommends which Large Programs should be scheduled. The Primary Assessors write consensus reports to reflect the final scientific assessment.

Queue Building

The primary outcome of the proposal review process is a scientifically ranked list of proposals. The list is generated using two main inputs: 1) the proposal rankings from individual reviewers in distributed peer review, and 2) the list of Large Programs recommended by the APRC.

In distributed peer review, each reviewer ranks their assigned proposals from 1 (strongest) to 10 (weakest). For each proposal, the least favorable (numerically highest) rank is discarded, and the remaining reviewer ranks are averaged to produce an average rank. These average ranks are then normalized within each scientific category onto a common scale, ensuring consistent treatment of proposals from different categories in the overall ranked list.

The ranked list of proposals establishes the priority order to build the observing queue. The Large Programs recommended by the APRC have first priority in building the queue, but they are limited to how much time they can fill in a configuration/LST, as described in the Proposer’s Guide. Creating the observing queue also takes into consideration the available time in specific configurations and LST ranges, time allocated to each ALMA Executive, and historical weather conditions for a given receiver band and frequency. It is during the queue-building stage that the priority grades (A, B, C) are assigned or declined depending on the amount of telescope time available. Because numerous factors are considered in building the queue, it is possible for a high ranked proposal to be declined while a lower ranked proposal is accepted.

After the ranked list is generated and the observing queue is created, the ranked list and the priority grades are submitted to the ALMA Director for approval. After the Director’s approval, the results are sent to representatives from East Asia, Europe, North America, and Chile for final approval. Principal Investigators are then notified of the results.