You are here: Home / News / Clarification of Large Program Policy

Clarification of Large Program Policy

Apr 11, 2016

Section 4.3 of the ALMA Proposers Guide states:

"The proposal team for a Large Program should not in parallel submit a Cycle 4 Regular Proposal that requests to do part of the science requested in the Large Program. Therefore, PIs, co-PIs and Co-Is of a Large Program cannot be a PI or a Co-I on a Cycle 4 Regular Proposal that duplicates observations (see Section 5.4) of their Large Program."

Clarification:  The observations for a Large Program should not in parallel submit one or more Regular Proposals that duplicates the observations of their Large Program; see Section 5.4 of the Proposers Guide and Appendix A in the Users Policies for the definition of a duplicate observation. Proposal teams may submit Regular Proposals that observe the same sources as their Large Program if the requested observations 1) are not formal duplicates (see example b below) or 2) are a subset of the required dataset (see example c below).

Examples: Submitting Large and Regular Proposals

A proposal team submits a Large Program to observe 100 galaxies in CO J=1-0.

The proposal team is also consider submitting in parallel the following regular proposals:

a) They want to submit three Regular Proposals, each of which will observe a subset of 20 galaxies in the Large Program, also in CO J=1-0 and to the same sensitivity and angular resolution as the Large Program.  The three Regular Proposals will be disallowed by the JAO since according to the ALMA Duplication Policy, the Regular Proposals duplicate observations in their Large Program.

b) The proposal team wants to observe one of the galaxies in the Large Program in CO J=1-0, but with three times better sensitivity than requested in the Large Program. These observations do not duplicate observations in the Large Program according to the ALMA Duplication Policy and are therefore a Regular Proposal is allowed. 

c) The proposal teams wants to observe one of the galaxies in the Large Program in CO J=1-0 and J=3-2. The CO J=1-0 observations will be observed to the same sensitivity and angular resolution as in the Large Program. Even though the CO J=1-0 observations are a formal duplicate of the Large Program, a Regular Proposal can be submitted if the proposal justifies why observations in both CO observations are required for the analysis.

 

Section 4.3 of the ALMA Proposers Guide states:

"A maximum of 15% of the time available for science observations will be dedicated to the execution of Large projects, corresponding to 450 hours of 12-m Array time and 270 hours of ACA stand-alone time (Sect. 5.1). To optimize the success in completing the observations within Cycle 4, 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 (see Sect. 5.3.3); and (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."

Clarification: The goal is to complete all A-ranked programs accepted in Cycle 4, including Large Programs, by the end of the observing cycle. The number of hours allocated to Large Programs has constraints as indicated above. The JAO will report on the scheduling feasibility of Large Programs to the APRC. It is strongly recommended that the time request for a Large Program not exceed the amount of time allocated for Large Programs in a given LST range.

Examples: Estimating scheduling feasibility for Large Program.

a) A proposal team wants to survey a sample of 50 galaxies at 1.5” resolution in Band 6. The galaxies are uniformly distributed between right ascension of 11h and 19h. According to the ALMA Observing Tool (see also Table A-1 in the Proposer’s Guide), the observations can be completed with 70 hours of time in the C40-1 configuration, including all calibrations.

Assuming the galaxies transit at reasonably high elevation, ALMA can observe the galaxies at approximately +/- 3 hours around transit. Therefore, the galaxies can be observed between ~ 8 LST and 22 LST, or for ~ 14 hours.  Therefore, ~ 70/14 = 5 days of Band 6 observing between 7 and 22 LST are required to complete the Large Program.

According to Table 3 in the ALMA Proposer’s Guide, approximately 17 PI observing days will be available in configuration C40-1. As indicated in Section 4.3 of the Proposer’s Guide, up to 50% of the time in C40-1 at a given LST range may be allocated to Large Programs, or ~ 8-9 days. Further, since the proposed observations occur predominantly during night times (see Column 4 in Table 3 of the Proposer’s Guide), all ~8-9 days are available for science observations.  (If the required LST range were during daytime hours, then only 4-5 days would have been available; maintenance, calibration, and development would take up the remaining time.) Finally, according to Table 2 in the Proposer’s Guide, approximately 70% of the time in C40-1 (~ 12 days) will have weather suitable for Band 6 observations.  Therefore, it is reasonable for a Large Program to request up to ~ 8-9 days of Band 6 observations at 1.5” resolution.

Since 5 days of observations between 7 and 22 LST are required for the observations, and 8-9 days are available to be scheduled for Band 6 Large Programs, the proposed Large Program would be judged to be feasible and low risk in terms of completing the requested observations within Cycle 4.

b) A proposal team wants to survey a sample of 200 protostars at 1” resolution in Band 7. The protostars are located at a right ascension of 18 hours. According to the ALMA Observing Tool (see also Table A-1 in the Proposer’s Guide), the observations can be completed with 60 hours of time in the C40-1 configuration, including all calibrations.

Assuming the galaxies transit at reasonably high elevation, ALMA can observe the protostars at approximately +/- 3 hours around transit. The protostars can then be observed between ~ 15 LST and 21 LST, or for ~ 6 hours.  Therefore, ~ 60/6 = 10 days of Band 7 observations between 15 and 21 LST are required to complete the Large Program.

According to the Table 3 in the ALMA Proposer’s Guide, approximately 17 observing days will be available in configuration C40-1. As indicated in Section 4.3 of the Proposer’s Guide, up to 50% of the time in C40-1 at a given LST range may be allocated to Large Programs, or ~ 8-9 days. Further, since the proposed observations occur predominantly during night times (see Column 4 in Table 3 of the Proposer’s Guide), all ~8-9 days are available for science observations. However, according to Table 2 in the Proposer’s Guide, approximately 40% of the time in C40-1 (~ 7 days) will have weather suitable for Band 7 observations.  Therefore, it is reasonable for a Large Program to request up to ~ 7 days of Band 7 observations in this configuration.

Since 10 days of observations between 15 and 21 LST are required for the observations, and 7 days of observations are available to be scheduled for Band 7 Large Programs, the proposed Large Program would be judged to be at risk to be completed during Cycle 4. 

In this case, the proposal team could reduce the risk by requesting 1” angular resolution for half of the sources, and 0.5” angular resolution for the other half, which will allow the observations to spread across more than one configuration.