• Title: ALMA Phasing System “Phase 2”

• Referee1

Grade: 3.0

Enabling Science with the ALMA Phasing System (Matthews)

1. Alignment with NA ALMA Partnership strategic goals;

Addresses strategic goal #1, "Improve and extende technical capability."

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

VLBI does not seem to be part of ALMA 2030.

The scientific case for mm VLBI in general is quite specialized but unique, and a few of those special cases are uniquely important -- most obviously, imaging the local surroundings of a black hole (the EHT). It is probably worth another $1M simply to do the best possible job for the EHT. ALMA's role in providing sensitivity is critical, and the nice north/south baselines also help.

The Haystack group has also done an amazing job so far, in getting VLBI working on ALMA. The proposed additions (especially fixing up the delays and allowing delay transfer from in-beam calibrators) are essential follow-ups to the basic capability, enabling much deeper observations of much fainter sources. Extensions to spectral line observations and other observing bands also seem obviously good ideas, where small investments will yield substantial new science. Single-dish VLBI is less exciting but also pretty simple to add.

3. Quality of the upgrade conceptual design;

Excellent. The upgrade described is pretty much what anyone would want, and the plan is informed by experience and ALMA realities.

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);

Could begin implementation immediately.

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

N/A -- all based at one institution

6. Qualifications of the key personnel of the Study;

The group is superbly qualified, as indicated by the success of the first phase of this project, and mm VLBI has been and remains their primary focus. Matthews in particular is deadly competent at whatever she turns her mind to.

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

See above. Very experienced group in both VLBI and radio interferometry in general; good history of working with ALMA.

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

Fairly low risk given the experience of the team and the success of the first phase of the project. As noted in the risk register, the project goals are ambitious, and may require a de-scope if the telescope is not available for necessary commissioning work, but this is alas the way things are at ALMA.

9. Strength of the Scientific Team supporting the Study;

Matthews again is superb, with an excellent grasp of the scientific needs and priorities. Fish & Crew have worked extensively on the primary scientific goal of the EHT.

10. Level of support guaranteed by the Institutes;

This is the primary research interest of the head of Haystack these days, so although no direct support is guaranteed, those involved will certainly have the full backing of the institute.

11. Budgeted cost of the Study;

Cost is primarily labor, and seems reasonable.

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• Referee3

Grade: 4.0

Title: ALMA Phasing System “Phase 2”

Alignment with NA ALMA Partnership strategic goals

ALMA is the linchpin of the Event Horizon Telescope. Clearly any further improvement of the sensitivity of the EHT is tied to technological developments in the ALMA phasing system. It definitely aligns with NA ALMA strategic goals

Strength of the scientific case for the proposed ALMA upgrade concept

The proposed enhancements would extend the work to weaker source, to frequency bands other than Band 6, and to lay the foundation for spectral line VLBI. All of these are timely developments, which are worthwhile.

Quality of the upgrade conceptual design

The concepts are sound and approach is methodological

Readiness for production in the context of the ALMA Development Plan The proposal demonstrates readiness. Strength of the consortium organization

The project is mainly done in MIT Haystack, with named participation from a staff member from each of the 4 institutes: SAO, Max-Planck, Onsala and ALMA. It seems that it is not much of a cooperative work.

Qualifications of the key personnel of the Study They are leaders of the EHT consortium. Technical expertise, past experience

The staff are already engaged in EHT work. They have the expertise.

Assessment of the level of risk inherent in the design Risk level should be low. Strength of the Scientific Team supporting the Study No dispute of the strength. Level of support guaranteed by the Institutes

This is where the question comes in. It is not clear from the proposal how much MIT Haystack is supporting the project.

Budgeted cost of the Study

It is noted that the proposal does not involve any hardware delivery, and about 90% of the cost is human resources related. If ALMA continues to commit a few nights per year to EHT operation, the funding of this proposal may not be as cost-effective for ALMA. A stronger statement from MIT Haystack on cost-sharing can strengthen the budget case of the project.

• Referee4

Grade: 1.5

Enabling New Science with the ALMA Phasing System “Phase 2” (Matthews)

1. Alignment with NA ALMA Partnership strategic goals;

This project is aligned with a number of the strategic goals, including introducing new software that extends the scientific capabilities of ALMA, and cultivating a relationship with the global VLBI community with member countries both within and outside of the ALMA consortium.

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

Exceptionally clearly written proposal, with clearly enumerated science goals, many of which, they authors note, are supported by previous and current funding; but several of which require funding from this proposal. The science sub-cases addressed in this proposal will be of interest to a far broader group of scientists than just continuum VLBI of point sources at 2 bands.

Needless to say, this plan furthers the goal of achieving the highest sensitivity possible on the longest possible baselines on earth, consistent with recommended development path #4 in the ALMA 2030 document.

3. Quality of the upgrade conceptual design;

Outstanding: this is a highly ambitious set of goals, but the completion of most or all of them will massively extend the user base of ALMA's VLBI capabilities. The goals are very clearly described and laid out; the years of experience the team has had working with ALMA are clearly evident in the scope of the "Phase 2" goals.

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);

Excellent: this is a follow-up on previous successful ADS projects, as well as work funded by other grants such as the NSF MRI. The team has been deeply integrated with the ALMA staff for years now, and will continue to take advantage of those connections and continue to foster what has hopefully been a healthy relationship between MIT and ALMA.

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

Excellent: the authors are a subset of the larger Event Horizon Telescope consortium, which has made breakthrough discoveries and technical advances year after year for the better part of a decade. Furthermore, if "consortium" can be construed to mean MIT + ALMA, the tight connection between the two groups as the APS has proceeded appears to have been highly fruitful.

6. Qualifications of the key personnel of the Study;

Excellent: the world's leading experts in (sub)mm-wave VLBI phasing.

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

Excellent: this team has been involved in the predecessor programs leading up to this project for many years, and has the skills and expertise necessary to execute this next phase.

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

Low: simply risk related to weather and normal (generally unforeseen) ALMA operations issues.

9. Strength of the Scientific Team supporting the Study;

Strong: the behind-the-scenes scientific direction of Shep Doeleman and others in the EHT collaboration presumably comprises the fundamental motivation behind this and all other EHT-related proposals.

10. Level of support guaranteed by the Institutes;

N/A, although the institutes have had funding from an NSF MRI grant and previous ALMA Development Fund studies; this proposal is an extension of already successful development efforts. There has also clearly been significant ALMA buy-in to this project, with lots of support from ALMA staff in all aspects of the "Phase 1" implementation.

11. Budgeted cost of the Study;

Reasonable, with no contingency.

• Referee7

Grade: 4.5

Title: Enabling New Science with the ALMA Phasing System "Phase 2"

1. Alignment with NA ALMA Partnership strategic goals;

This is a proposal for follow-on work to improve and extend the ALMA phasing system, which has now been deployed and used successfully for VLBI observations in coordination with other millimeter-wave observatories. The prior work and proposed work fit within the NA ALMA strategic goal to implement infrastructure upgrades that increase scientific capibility.

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

The VLBI science case is very strong, given the geographic location of ALMA as well as its collecting area. As the proposal notes, in millimeter VLBI networks, baselines containing ALMA bring order-of-magnitude sensitivity gains over others.

The proposed upgrades will significantly increase the range of VLBI projects that will be able to take advantage of ALMA. In particular, subarray VLBI modes, when they offer sufficient sensitivity, would enable ALMA to participate in VLBI runs simultaneously with other ALMA observing. This would improve VLBI scheduling flexibility and reduce disruption to mainline observing associated with coordinated VLBI runs.

The ALMA 2030 roadmap is silent on VLBI, but recognizes the scientific value of extending ALMA itself to longer baselines. Some of the astrometry-related science case for extending ALMA certainly applies as well to enhancing ALMA's VLBI capabilities and efficiency. Ideally, ALMA would be able to fund continued VLBI development along with the upgrades envisaged in the roadmap. However, among the ALMA 2030 priorities, improvements in receiver bandwidth and sensitivity, and improvements to data processing and archive management should come ahead of VLBI.The other roadmap priorities, multi-beam receivers and extending ALMA baselines, are arguably less important in the near term than building a flexible, robust VLBI capability.

3. Quality of the upgrade conceptual design; 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 conceptual design and readiness for production of the proposed work is strong. This is natural given that the proposed work is part of a staged program, and the first stage has been successfully implemented.

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

This work is proposed by a single organization (MIT Haystack), with individual collaborators at other institutions.

6. Qualifications of the key personnel of the Study;

The key personnel are highly qualified VLBI experts with a proven track record, including with stage 1 of the APP.

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

The hardware component of the APP was essentially completed in phase 1. The work in this proposal is mostly software. The proposers are very well qualified to continue this work.

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

Risk is minimal, and mainly associated with availability of test time on ALMA. The proposed work consists of a number of largely independent projects. Failure to complete any one of them would have little impact on the others.

9. Strength of the Scientific Team supporting the Study;

The scientific team (Matthews, Fish) is very strong, with deep related experience.

10. Level of support guaranteed by the Institutes;

Institutional support is appropriately certified.

11. Budgeted cost of the Study;

Cost is reasonable at $208K / FTE, with no additional cost for external collaborators.

Comment

• Supplemental Reviews
• Referee5

Grade: 3.3

APP Very qualified team, very detailed and clear presentation of work. Science case affects fewer projects than others. Doesn’t directly connect to ALMA2030, but extends capabilities and therefore matches NA ALMA goals. Clearly ready for implementation, and though labor cost is not insignificant, the team’s experience and real success in delivering the APS thus far suggests that their estimates are very credible.

-- AlWootten - 2017-05-09