* Referee5

Grade: 2

485 - A Significant Upgrade to the ALMA 64-Antennna Correlator

1. Alignment with NA ALMA Partnership strategic goals;

This development doubles the bandwidth of the correlator, which is well aligned with the NA goals.

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

Increasing the bandwidth is one of the recommendations of ALMA 2030. The scientific return of increasing the bandwidth is large, the sensitivity gain achieved thereby is much more cost effective than buying more antennas. There is already a need for higher spectral resolution at the lower-frequency bands and this need will become significantly more acute with band 1. This development would address that need as well.

3. Quality of the upgrade conceptual design;

The strength of this design is the relatively low risk. This is the straightforward extension of the current system and would plausibly be non-disruptive to the array. If done soon and at affordable cost, it improves ALMA in very useful ways. It does several other things, including increasing spectral resolution, channel count, providing fast readout, and memory depth needed for long baselines. To make full use of this correlator requires front-end upgrades in many bands, which makes it a conservative approach to expansion.

Under this conservative approach the number of available channels does not go up dramatically (8x, but the total bandwidth at the highest resolution is still small). This sacrifices some of the richness of the acquired data. Another downside is that the digitization and filtering paradigm remains unchanged (“4GHz” still means 3.75 GHz of usable bandwidth, a difference that is problematic for spectral surveying when the IF starts at 4GHz). A less conservative approach would reconsider the digitization to resolve this problem. This issue is mostly in the inextricably linked EU development, not this development.

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);

This development ready for production.

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

This project relies on a parallel development in EU to fully realize the improvements it can provide, but if ALMA deems this effort worthwhile then the sharing of cost between two regions will be a strength.

6. Qualifications of the key personnel of the Study;

The team is qualified to deliver this updated version of the current correlator. A weakness of the organization, one acknowledged in the proposal, is that it relies on retired and near-retired personnel to complete it, which presents some risk.

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

The team is intimately connected to the ALMA correlator and is therefore fully qualified.

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

This is a low-risk development. They note a 10% chance of making an error in the ASIC design that would compromise the production run, I hope that there is enough review and simulation that the probability is lower than this.

9. Strength of the Scientific Team supporting the Study;

The scientific lead is an experienced ALMA hand with a wide view of the science program.

10. Level of support guaranteed by the Institutes;

N/A

11. Budgeted cost of the Study;

The project cost is dominated by materials. This is not an inexpensive development project, but it is not burdened by a large salary component (<11 FTE-yr).

* Referee6

Grade: 2 (science grade alone) 4 (science and cost - see 8 and 11 below)

A Significant Upgrade to the ALMA 64-Antenna Correlator

1. Alignment with NA ALMA Partnership strategic goals;

This proposal aligns with the strategic goals in many ways. It improves and extends the technical capabilities. It also increases operating efficiency. The proposal also aligns with ALMA 2030.

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 for the proposed upgrade is excellent - access to wider bandwidth, narrower spectral features, and better sampling, along with flexibility.

3. Quality of the upgrade conceptual design;

Looks excellent but should be reviewed very carefully by an expert in correlators. I note that the conceptual design study is only recently completed but that the output from that study should be very carefully externally reviewed by technologists to determine feasibility and provide confidence in the cost.

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 proposers believe that they are ready and that 4 years is needed to complete the project. Given that the conceptual study has only just completed and many documents were produced for the study, this should be externally verified by technological experts.

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

Excellent.

6. Qualifications of the key personnel of the Study;

Excellent.

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

Excellent record.

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

While the individual risks are low, the possibility of ASIC production issues does raise a large monetary risk of $2M (even if there is only a 10% likelihood). Given the funding envelope for this call, this is actually an extreme risk.

9. Strength of the Scientific Team supporting the Study;

N/A - Al Wooten is named as the Scientific Lead but is only expected to provide 1% of his time to the project.

10. Level of support guaranteed by the Institutes;

Small but includes one retired individual which seems strange (perhaps I am misreading the tables).

11. Budgeted cost of the Study;

$10,915,986 - which if I understand correctly is way over the amounts available even if only the first two years is funded (since that is where the large outlays take place).

* Referee8

Grade: 4.0
because this gives a significant improvement in science throughput

Title: A significant upgrade to the ALMA 64-antenna correlator
PI: Lacasse

1. Alignment with NA ALMA Partnership strategic goals;

The proposal is well aligned with the strategic goal of increasing the performance of ALMA, in this case by increasing the correlator bandwidth. Increased continuum sensitivity and larger bandwidth at each spectral resolution will improve the overall efficiency of ALMA.

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

The science case in the proposal is based on improving speed. What will be done with the upgraded correlator is not qualitatively different from what is being done now, but there will be more of it.
The proposal directly addresses the ALMA 2030 recommended development path of improving speed by increasing bandwidth. In this case, the improvement is a factor 2 in bandwidth, which represents a modest step towards the ALMA 2030 goal of processing an entire receiver band in one go.

3. Quality of the upgrade conceptual design;

The upgrade is well thought out and the plans are well developed. I see no technical reasons why the approach will not succeed.

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 upgrade is ready for implementation.

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

Most of the work will be done by NRAO, so the project organization is simple. That is an advantage.

6. Qualifications of the key personnel of the Study;

The key personnel are well qualified to do the work.

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

The proposal includes key staff from the original ALMA correlator project, and facilities that were developed for that original project, so the experience and expertise are appropriate.

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

This is a conservative, low-risk upgrade that retains much of the existing correlator infrastructure.
I have some concerns:
(1) Success depends on a sampler upgrade that is not part of the proposal. ALMA needs to ensure that the sampler work is done, or the correlator upgrade will not make sense.
(2) The proposal risk assessment includes retirement of a key resource and a key contribution that is in-kind. These are significant risks, and I do not believe the $ impact assigned to them.
(3) Reusing cables, power supplies, etc. from the original correlator reduces costs, but may result in end of life issues.

9. Strength of the Scientific Team supporting the Study;

The science case for the correlator upgrade is part of the broad science case for ALMA 2030.

10. Level of support guaranteed by the Institutes;

Appropriate.

11. Budgeted cost of the Study;

$11M seems a reasonable total cost for a factor 2 increase in bandwidth of the ALMA correlator.

* Referee9

Score 7

A Significant Upgrade to the ALMA 64-Antennna Correlator PRINCIPAL INVESTIGATOR: RICHARD LACASSE

Double the bandwidth and increase the resolu2on of the correlator by developing a new custom correlator ASIC 32 2mes more complex than the current ASIC. This requires replacing most of the 2000 cards in the signal path.

Parallel project at Universite de Bordeaux to upgrade the digi2zers, the Data Transmission System (DTS) and the digital filters. Upgrades to other systems are required to take advantage of this upgrade.

System tests will be conducted in CharloNesville using “the fiPh quadrant" Fast, and inexpensive path to enhanced performance .

Performance: 8GHz dual pol x 64 antennas x 1 kHz resolution. Support for phased array and 1 ms sample. Cost $10.9M Risks include retiring key personnel, and multiple ASIC fabrications.

* Referee10

Grade: 6

Executive Summary: This project proposes to replace the ALMA correlator to increase bandwidth and spectral resolution, using incremental improvements to the technologies employed in the existing correlator. I am concerned that the upgrade seems premature (compared to other components in ALMA), does not leverage new technologies or techniques, gives no path to further upgrades short of another complete replacement, and is dependent on a very small number of key personnel. It strikes me as a low-risk, low-reward proposal.

Lacasse, Richard - A Significant Upgrade to the ALMA 64-Antennna Correlator ALMA Development Review

1. Alignment with NA ALMA Partnership strategic goals;

The proposal is well aligned with Strategic Goals (1.1) and (1.3), as it does provide a significant upgrade to the existing correlator, and by doubling the instantaneous bandwidth processed the observing efficiency for some science cases is doubled (related to 2.1). Unfortunately, it does little to address other areas: operating cost (3.x) and practices (2.2) appear unchanged, no advantage is made of new software or hardware beyond the growth under Moore’s law (1.2), nothing is done to include young researchers (5.x), while the expertise of those who build the original correlator is exploited, it is not leveraged into the broader community in an significant way (4.x).

2. Strength of the scientific case for the proposed ALMA upgrade concept; Comment on the relevance to the †̃ALMA 2030â€TM development documents. By broadening the band of the correlator, this proposal provides a requisite subset of the technology needed to address point 2 of the ALMA2030 document, “Larger Bandwidths and better receiver sensitivity”. Significant additional front-end hardware is still required to fully address the point, but the correlator itself is a significant contribution.

3. Quality of the upgrade conceptual design;

The conceptual upgrade proposed here is a straightforward extension of the existing correlator design. No significant innovation is proposed, and it appears there is no attempt at leveraging of significant developments in the field over the past decade. The design seems a “safe” upgrade path, in that it uses the same technologies as the existing system, but it provides little room for further growth or later observing modes, short of another complete replacement. This has the feel of an incremental upgrade, not a significant advance for the instrument.

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 upgrade appears to be at a suitable stage of development for full production to begin. Given that it requires significant frontend upgrades to fully leverage the expanded bandwidth, however, the timing seems somewhat premature: an upgrade correlator arriving years before an upgraded frontend doesn’t do anyone much good, and it seems odd to first deploy upgraded digital electronics, where one is generally best off buying at the last minute to fully leverage industry developments.

5. Strength of the consortium organization (if applicable); The proposing organization is NRAO, so I have no concerns about the abilities of the institution. Barring larger funding questions, they are in a strong position to make this contribution.


6. Qualifications of the key personnel of the Study; The proposers who have a track record in this area, having worked on and delivered the original correlator. They have all the necessary experience & expertise.

7. Technical expertise, past experience (also in series production, if relevant) and technical facilities in the Institutes taking part in the Study; No concerns here, the team has executed a correlator in the past and I believe they have the needed facilities and experience.

8. Assessment of the level of risk inherent in the design; As a nearly part-for-part replacement of the existing correlator, by the people who know the system best, there is very little risk involved in this proposal. The requirement for broader-band digitizers (and broader-band frontends) could limit the immediate usefulness of the proposed system. The project seems largely dependent on a handful of key personnel: only 4 devoting the majority of their time to it, of which only 2 are currently know, one of which (the PI) is anticipated to retire during the project. I have serious reservations about the long-term viability of this staffing. 
 9. Strength of the Scientific Team supporting the Study; Only one member of the Key personnel is listed as part of the scientific team (Scientific Lead), and it does not appear that a significant scientific team is supporting this proposal. Nonetheless, the scientific case for a broader band and higher spectral resolution is clearly laid out, and I think well justified. 
 10. Level of support guaranteed by the Institutes; The NRAO is providing significant in-kind in the form of key personnel, but this constitutes a small fraction of the overall project cost.


11. Budgeted cost of the Study; At >$10M, the cost of this upgrade is significant, but largely in-line with what would be expected for a next-generation correlator. Since it follows a well-trod technology path, this forecast is likely reliable.

-- AlWootten - 2017-05-04
Topic revision: r3 - 2017-06-27, AlWootten
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