• Proposal 518: Full-Mueller Mosaic Imaging with ALMA

  • Reviewer 2

Grade: Very Good/Excellent (1.3)

Title Full-Mueller Mosaic Imaging with ALMA (PI: Bhatnagar)

1. Alignment with NA ALMA Partnership strategic goals;

The proposed Study is well aligned with at least two of the ALMA strategic goals, namely improving the technical capability of ALMA (through improved software) and strengthening the North American radio astronomy community, primarily by attracting a Ph.D. level candidate and potentially by interacting with South Africa (Co-I: Jagannathan).

2. Strength of the scientific case for the proposed ALMA upgrade concept; Comment on the relevance to the "ALMA 2030" development documents.

The proposed Study focuses on increasing the fidelity of mosaic (wide-field) imaging. The specific science case identified is tracing the magnetic fields shape molecular cloud infall and protostellar jets. However, as the proposing team notes, there is a wide variety of other scientific cases that would benefit from improved wide-field imaging. More generally, the relatively small fields of view for ALMA antennas are a commonly noted restriction within the community on ALMA's performance. Enabling higher fidelity, wide-field imaging is likely to benefit a substantial fraction of the community. Finally, while not strictly a scientific benefit, ALMA public outreach is likely to benefit from being able to present images that are larger (and higher fidelity) than previously available.

The focus of this Study is higher fidelity, wide-field imaging. While not identified specifically in the "ALMA 2030" roadmap, higher efficiency wide-field mapping is identified. The recommended approach for that goal is multi-beam receivers, but the proposed Study appears consistent with the spirit of that goal.

3. Quality of the upgrade conceptual design;

The proposed Study has a clear and straightforward path toward obtaining the proposed technical improvements. The antenna polarization performance will be simulated, the modeled antenna polarization patterns will be compared with existing data and modified to match existing data, and the models will then be incorporated into the analysis software. There are already some models for the ALMA antennas (though with likely faults in them) and there are existing data (with potentially more to become available during the course of the Study). Thus, not only is the approach reasonable, the risk of being able to execute at least the first two items is judged to be low.

There may be a higher risk than the PI assesses for the ease of incorporating the improved models into the analysis software (CASA) and whether the improved software produces images in a reasonable duration. In part, the proposed Study is dependent upon a software engineer and CASA has long-standing issues of not executing rapidly.

4. Readiness for production in the context of the ALMA Development Plan (the aim is to support a range of upgrades including both those which can be implemented rapidly and those requiring longer-term research and development);

The proposed Study is work that could be implemented relatively rapidly. As noted above, there are existing, albeit imperfect, models, data, and software. The risks noted above could slow the Study, but not substantially enough that significant improvements would not occur over the next 12 mon.--18 mon.

5. Strength of the consortium organization (if applicable);

N/A, or only slightly. Most of the individuals are from NRAO, save two individuals (affiliated with Univ. Cape Town and NAOJ), though their levels of effort are low.

6. Qualifications of the key personnel of the Study;

The team is a strong team. The PI is well known as an expert in radio interferometric imaging, and the Co-Is have a range of science interests that enable them to provide feedback on the performance of the improved imaging.

7. Technical expertise, past experience (also in series production, if relevant) and technical facilities in the Institutes taking part in the Study;

Largely covered in item #6. The team has strong technical expertise in this area.

8. Assessment of the level of risk inherent in the design;

The team's assessment of risk (Low) is reasonable, though CASA has a well-known reputation for being slower than advertised. The computations associated with the improved algorithm within CASA could result in a capability that is sufficiently slow in execution that it is only rarely used.

9. Strength of the Scientific Team supporting the Study;

Largely covered in item #6, but it is a strong team, albeit one in which no one individual is making a substantial contribution. The proposal could have been stronger had a smaller number of science Co-Is with a larger involvement been planned.

10. Level of support guaranteed by the Institutes;

The only level of (in-kind) support is provided by individual researchers contributing their research time, in addition to standard items such as an office and computer.

However, the contribution of individual research time by the researchers partially mitigates the concern expressed in item #9 and is comparable in value to the overall Study budget.

11. Budgeted cost of the Study;

The cost is judged to be reasonable. One potential budgetary weakness is that no cost is allotted for publishing or presenting results. If the Study is successful, the results may be less used than they otherwise would be because of lack of awareness.

  • Reviewer 5
Grade: 2

FULL-MUELLER MOSAIC IMAGING WITH ALMA

1. Alignment with NA ALMA Partnership strategic goals;

The proposed development study aims to rectify one of the outstanding issue with ALMA in terms of full polarization across the primary beam. This study is crucial for ALMA to yield is maximal scientific return.

2. Strength of the scientific case for the proposed ALMA upgrade concept; Comment on the relevance to the ‘ALMA 2030’ development documents.

While not specifically related to the ALMA 2030 upgrade concepts, polarization is the only way to characterize the strength and morphology of magnetic fields at the wavelengths ALMA is sensitive to.

3. Quality of the upgrade conceptual design;

The conceptual design appears sound. Numerous background studies have been conducted with regard to the polarization calibration by the investigators and the proposed development study is the next logical step toward fully unlocking ALMA's polarization potential.

4. Readiness for production in the context of the ALMA Development Plan (the aim is to support a range of upgrades including both those which can be implemented rapidly and those requiring longer-term research and development);

With the background studies that have already been conducted, the authors have proposed a clear path forward to characterize the direction dependent polarizaiton leakage.

5. Strength of the consortium organization (if applicable);

NRAO/JAO is the best organization to perform this study with all the key personnel.

6. Qualifications of the key personnel of the Study;

The study includes some of the most proficient personnel to undertake this study. Most of the team has been contributing to the various polarization commissioning efforts and are intimately familiar with the challenges presented and the proper paths forward.

7. Technical expertise, past experience (also in series production, if relevant) and technical facilities in the Institutes taking part in the Study;

The team has all the requisite expertise needed to undertake this project.

8. Assessment of the level of risk inherent in the design;

The risk assessment is reasonable, through all the ALMA commissioning work the necessary paths forward have been identified. The Software engineer hire could pose more risk if the interested person is not available by the time funding is awarded.

9. Strength of the Scientific Team supporting the Study;

Science team is also excellent, having produced somes of the ground-breaking work on magnetic field observations. The PI is also dedication personal research time to this effort.

10. Level of support guaranteed by the Institutes;

The support offered by NRAO in terms of co-investigator functional time is excellent.

11. Budgeted cost of the Study;

The proposed study comes in high in terms of cost, but also has some of the most detailed background work performed in order to identify the path to enable full polarization calibration on ALMA.

  • Reviewer 6

Grade: 3.5

Title Full-Mueller Mosaic Imaging with ALMA by Sanjay Bhatnagar

Alignment with NA ALMA Partnership strategic goals.

Proposed study would improve and extend capabilities for scientific research. It also nurtures relationships with young individuals with the potential to become the next generation of technicians, engineers, and scientists.

Strength of the scientific case for the proposed ALMA upgrade concept. Comment on the relevance to the ‘ALMA 2030’ development documents.

It is relevant to the recommended development path of enabling efficient mapping. The full polarization doesn’t necessarily increase the efficiency, but ensures scientific robustness of results. The proposal described in detail one science case, but listed many that could be affected. Quality of the upgrade conceptual design The path described seemed appropriate way to tackle the problem. I was a little taken aback by the comment in the proposal about using the data from the full polarization holographic measurement made with the artificial beacon, if it becomes available. I can’t judge which is better; I got the sense that these measurements would be superior, so surprised that there is no discussion of this.

Readiness for production in the context of the ALMA Development Plan (the aim is to support a range of upgrades including both those which can be implemented rapidly and those requiring longer-term research and development).

The project would result in a deliverable: primary beam model, and simulator. Strength of the consortium organization (if applicable)

N/A Qualifications of the key personnel of the Study

The PI wrote the A projection code in use for the EVLA.

Technical expertise, past experience (also in series production, if relevant) and technical facilities in the Institutes taking part in the Study.

See above. Assessment of the level of risk inherent in the design

Low level of risk. Strength of the Scientific Team supporting the Study

Has a mix of NRAO staff familiar with CASA and ALMA. Level of support guaranteed by the Institutes

There is significant in-kind contribution from Co-Is who will lend their time to the study. Budgeted cost of the Study

Seems high; not clear what the $63k contributed time from PI is.

  • Reviewer 7

Grade: 0.1

Title FULL-MUELLER MOSAIC IMAGING WITH ALMA

1. Alignment with NA ALMA Partnership strategic goals; This project aligns with the strategic goals: ● 1. Improve and extend technical capability by improving and extending capabilities for scientific research (1.2) And has the potential to align with ● 2. Create more observing time by continuously improving processes, practices and procedures by improving the efficiency with which polarization observations can be obtained (2.2) ● 5. Strengthen the North American Radio Astronomy community by engaging a PhD student to work on the project (5.2)

2. Strength of the scientific case for the proposed ALMA upgrade concept; Comment on the relevance to the “ALMA 2030” development documents. The scientific case is very strong. The characterization of the ALMA antennas primary beams (PBs) and direction dependent and independent polarization leakages can dramatically expand the types of polarization science that ALMA can address. The current inability to map polarization over areas larger than ~⅓ the PB is a significant deficit in ALMAs promised capabilities. This proposal has some relevance to the ALMA 2030 goal of 4. Increasing wide field mapping speed: enabling efficient mapping, in that wide field polarization mapping is currently impossible, so any improvement increases the wide field (polarization) mapping speed.

3. Quality of the upgrade conceptual design; The design and plan of attack is well thought out. The more straightforward task of developing the PB models can effect immediate improvement in existing imaging algorithms, even for Stokes-I data. These models are expected to be produced early in the study period. The second goal of characterizing the leakages

4. Readiness for production in the context of the ALMA Development Plan (the aim is to support a range of upgrades including both those which can be implemented rapidly and those requiring longer-term research and development); Some of the results of this study, such as the PB models and the expected EFP (via geometric optic simulation), are applicable in the short term for imaging and observational planning. The larger effort involving adapting the existing imaging software and deploying the software on High Performance Computing would be used as the basis of a future Development Proposal.

5. Strength of the consortium organization (if applicable); N/A

6. Qualifications of the key personnel of the Study; As one of the leading experts on this kind of characterization of radio antennas, the PI is extraordinarily qualified to supervise and contribute intellectually to this study. The rest of the team carry expertise in magnetic field observations, calibration techniques, antennas and receivers, interferometric data reduction, ALMA operations, etc.

7. Technical expertise, past experience (also in series production, if relevant) and technical facilities in the Institutes taking part in the Study; High technical expertise and past experience within NRAO.

8. Assessment of the level of risk inherent in the design; The risk is low in that the problem is well understood and well formulated. There is significant risk mitigation possible through the use of the PIs research time. The use of existing ALMA data and geometric optics simulation rather than relying on new data is wise (though the proposal’s plea for a full-polarization holographic measurement using the signal beacon is well reasoned and ought to be granted).

9. Strength of the Scientific Team supporting the Study; See #6.

10. Level of support guaranteed by the Institutes; Support of PIs research time by NRAO (0.5 FTE) is significant.

11. Budgeted cost of the Study; Cost is reasonable, in-kind contributions reasonable. -- AlWootten - 2017-07-19
Topic revision: r2 - 2017-07-19, AlWootten
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