Science Highlight




ALMA Cycle 4 Information for Large Programs

As indicated in the Pre-announcement for the Cycle 4 Call for Proposals, the Joint ALMA Observatory (JAO) will accept proposals for Large Programs for the first time in Cycle 4. This announcement provides guidelines to prepare a Large Program proposal.

Definition of a Large Program

Large Programs are defined as projects that request more than 50 hours of observations with either the 12-m Array or the Morita Array (a.k.a. the ALMA Compact Array, or ACA) in stand-alone mode. Large Programs for the 12-m Array may include ACA for short-spacing observations as needed.

A Large Program can only request standard observing modes. The standard observing modes offered in Cycle 4 are listed in the Pre-announcement for the Call for Proposals. Requests for Target of Opportunity and time-critical observations are not permitted in Large Programs in Cycle 4.


Proposal format

The proposal format for Large Programs differs from regular ALMA proposals in two aspects:

1)    The Scientific Justification for Large Programs will be allotted two additional pages for a total of six pages. Within this page limit, the proposal must present a scientific justification, figures, tables, a description of data products, and a management plan.

2)    In addition to the Principal Investigator (PI) and co-Investigators, Large Programs may designate any number of co-Principal Investigators (co-PIs). The requested observing time will be split among the regions (North America, Europe, East Asia, and Chile) based on the proportionality of the Executive affiliation of the PI and co-PIs.

Time Available for Large Programs

It is anticipated that 3000 hours will be offered for the 12m Array and 1800 hours for the ACA in Cycle 4. Up to 15% of this time may be allocated to Large Programs; i.e., 450 hours for the 12m Array and 270 hours for ACA stand-alone.

Review procedure

The ALMA Proposal Review Committee (APRC) will recommend which Large Programs should be scheduled with guidance from the ALMA Review Panels. A Large Program must receive a Grade A from the APRC in order to be scheduled. Since the APRC consists of the Chairs of each review panel, with expertise ranging from the solar system to cosmology, the scientific goals of a Large Program should be recognized as important by the broad scientific community.

Review criteria

Large Programs will be evaluated based on:

1)    Scientific merit

A Large Program should address strategic scientific issues that will lead to a breakthrough in the field, and be a coherent science project not reproducible by a combination of smaller regular proposals.

2)    Technical feasibility

A Large Program should fully justify the requested sensitivity, the correlator setup, and the imaging requirements. The observations should be consistent with observatory best practices unless justified in the proposal.

3)    Scheduling feasibility

A Large Program should be designed such that the observations can likely be completed within Cycle 4 given the antenna configuration schedule and weather constraints. Further guidance on scheduling feasibility is provided below.

4)    Data products

A Large Program should describe the data products that will be produced to achieve their science goals. The project teams will be expected to deliver these data products to ALMA so that they can be made available to the community at large.

5)    Management plan

A Large Program should present a management plan that describes a schedule of work, a description of the roles of the proposal team, a timeline to deliver data products to ALMA, and a plan to disseminate the results.

Scheduling Feasibility

To optimize the success in completing the observations, the following scheduling constraints will be imposed when selecting Large Programs:

  1. The time allocated to Large Programs shall not exceed 33% of the available time for a given LST range on antenna configurations with baselines longer than 5 km (configurations C40-8 and C40-9)
  2. The time allocated to Large Programs shall not exceed 50% of the available time for a given LST range on configurations with baselines shorter than 5 km.

The best time of day for ALMA observations in terms of sky opacity and atmospheric phase stability is approximately two hours after sunset until about 4 hours after sunrise. A large time request for Band 7 daytime observations on the 12m Array is discouraged.

Table 1 summarizes the planned configuration schedule, the approximate LST range that provides the best observing conditions, and the approximate number of days available for observations after array calibrations, weather, and development activities. Approximately half of the daytime hours will be devoted to software and hardware maintenance. The number of days available for observations in a configuration is only an estimate, as the configuration schedule may be modified depending on the proposal pressure in Cycle 4.

Table 2 lists the estimated percentage of time suitable in the 12 m Array for the four bands available to Large Programs.

Table 1: Planned Array Configuration Schedule and estimated days available for science observations

Table 2: Estimated percentage of observing time suitable for Science Observations on the 12m Array for the four Bands available to Large Programs