Summary of Recommendations Sep 2006
1. The ASAC supports the proposed extended CSV schedule, and consequent later start to 
Early Science but with a much enhanced array. 
2. The ASAC highlights the need to pursue a diligent and continuous effort to identify and 
recruit the best staff for the CSV team, and identify incentives to attract and retain such
staff. 
3. The ASAC recommends that the best support be provided to the Project Scientist in terms of resources to support communication, administration, documentation and delegation in order to accomplish CSV according to the planned schedule. 
4. The ASAC was very supportive of the idea that there be two commissioning scientists to 
support the project scientist in the day-to-day execution of his/her duties, and to help with 
the retention of knowledge on progress as staff rotate in and out of the OSF. 
5. ASAC recommends that ALMA consider the creation of a sabbatical visitor program to 
assist the project scientist to continue commissioning once ES begins, and the array grows 
beyond 15 antennnas. 
6. The ASAC recommends that the Project Scientist and the Science IPT should develop a 
more detailed list of observing modes, and that the ASAC should revisit this charge when 
this work is more advanced. 
7. The Committee strongly recommends that the CASA release schedule be constantly scru- 
tinised to ensure it meets the requirements of ALMA for early community testing, and Early 
Science observations with ALMA. 
8. The ASAC recommends that external users be included in CASA beta testing in addition to 
NRAO users, with the goal of having the software available to a broad community before 
the start of Early Science. 
9. The ASAC endorses the plans to include the community in workshops and committees 
which will begin the process of identifying and prioritizing new capabilities for ALMA 
in the operations phase. 

Summary of Recommendations Jan 2006 
1. The ASAC recommends that the project urgently consider the final optimization of the two 12m antenna designs, such as setting the shape of the inner parts of the feed legs to reduce ground spillover, tilt of the subreflector, etc. These issues, which could result in real sensitivity gains, need to be settled before the contractors finalize the design, since further changes then become very expensive. 
2. The ASAC recommends that the Antenna or System Engineering IPT perform EM modeling to get an estimate of the primary beam, in particular a good measure of the first sidelobe, which may dominate mosaic image fidelity. These modeling results should then be compared to the predictions from the holography data for the two prototype antennas by the Science IPT.. 
3. The ASAC recommends that the Science IPT continue its effort on wide-field polarization and mosaic simulations. In particular, new algorithms allowing deconvolution with two (or more) primary beams need to be developed for ALMA. 
4. The biggest continuing risk for the science software is that expert users may fail to adopt the new software and that the software may prove difficult for novice users to learn. The ASAC recommends that a solid plan be formulated to minimize these risks as the system becomes available to users. 
5. The ASAC recommends that the commissioning team be fully committed to using the ALMA science software during commissioning. Conversely, the Software IPT must be committed to giving first priority to supporting the commissioning effort once it is underway. 
6. The ASAC recommends that the Computing IPT review the FTE requirements to support science software testing and exercising in 2008-2009 and commissioning support in 2007-2010. It is essential that sufficient resources are available to deliver software that functions well to the user community in time for Early Science. 
7. Since the addition of the ACA to ALMA adds a number of possible observing modes, the ASAC recommends that the project carry out an analysis of what calibration techniques will be most appropriate for the various modes that include the ACA 7m array.
8. The ASAC recommends that the observing technique of chopping during on-the-fly (OTF) scanning of the total power antennas and its effect on the data quality be studied carefully. 
9. The ASAC recommends that the project carry out a detailed study of the scheduling impact of all modes offered by the enhanced ALMA. 
10. The ASAC recommends that the DRSP be updated to include new projects for Bands 4, 8, and 10, as well as more detailed information related to the ACA. 
11. The ASAC recommends that a fully-integrated and properly resourced Outreach and Public Relations IPT be formed. This IPT must ensure that ALMA has a single public face that reflects the scientific excitement and technological excellence of the project.

ALMA SC I E NT I FI C ADVI S ORY COMMI T T E E RE P ORT, OC TOB E R 2 0 0 5 12 
8 Summary of recommendations 
1. With the possible exception of BCP No. 1, we strongly suggest not to implement any of the BCPs marked as “MA” and BCPs 5 and 10 (WVRs and Software). 
2. Although these have lower priority with respect to the other items considered above, we suggest to carefully consider the cost-to-impact ratio before accepting any of BCPs 6a, 6b and 7b (Solar Filters, 1/4 Wave Plate for Band 7, and Subarrays). 
3. We endorse the 50-antenna array proposed by the project, and recommend no further reduction in antenna number is made. We also strongly endorse the goal of building 64 antennas if further funds become available. 
4. We suggest adopting BCPs 3, 4a-g, 11, and 12 (OSF Residence, Miscellaneous Site, Travel and Site Characterization. 
5. We suggest to adopt the Science Requirements Document following minor revisions, but note that this document will have to be updated when the rebaselining process will be completed. 
6. We propose a Programme Review Committee structure with an International Programme Review Committee empowered to merge ranked lists from Regional PRCs and solve possible duplications. 
7. We believe that, at this time, no provision needs to be made for special projects like Large or Legacy Proposals. 
8. The structure and policies of the ALMA PRC should be periodically reviewed to monitor and ensure the maximum scientific output of ALMA. 
9. We suggest to split the demonstration science concept into Science Verification activities and ALMA Public Images. 
10. We propose to adopt the inner (within 4km) ALMA configuration design document. 
11. We note the difficulties within each region and the JAO in the ramping up of the ARC and operations planning activities. We recommend to hire key personnell in these areas as soon as 
possible.

1 Executive Summary and Recommendations Feb 2005
The ASAC considered two charges from the ALMA Board at its February meeting in Garching. 
As part of Charge 1, the Committee discussed rescope options for ALMA, identified during the rebaselining process, which would mitigate the impact on the science while achieving cost savings to the Project. The Committee identified a number of acceptable options, including postponement of the implementation of two of four planned subarrays, reduction in the number of pads through a reoptimized configuration design, and delay in the implemention of the largest, Y+ array. Options presented by the Project that were deemed unacceptable by the Committee in terms of the serious impact on science were delays in the implementation of one of the two polarizations, one of the two IFs, or three of the four sub-arrays. 
The issue of the scientific impacts of a number of antennas smaller than the original 64, corresponding to 601 operating antennas, is more complex. This portion of Charge 1 was discussed extensively by the Committee in Garching. The ASAC has previously stated, in its report of September 2004, that a 10% decrease in the number of antennas from the baseline project would have tolerable impact on the science, and would not rule out any of the Primary Scientific Requirements. The Committee believes that a submillimeter array with 50 or more operating antennas would be a superb instrument that would surpass all existing arrays by a wide margin. The scientific capabilities of such a powerful continuum and line instrument at the high and dry Atacama site will be remarkable and unique.  ALMA will be a spectacular complement to concurrent facilities such as SPITZER, SOFIA, Herschel,  James Webb Space Telescope, and large ground-based optical telecopes. 
On the other hand, the original specification of 60 operating antennas was driven by the need to do groundbreaking submillimeter science at the highest resolutions. Studying galaxies in the early universe requires the highest sensitivity and resolution, and is a Primary Scientific Requirement of ALMA. Equally strong requirements are placed on resolution and sensitivity by the imaging of structure and kinematics in the gas and dust of nearby protoplanetary disks on scales comparable to the gaps created by planets, which is the second Primary Scientific Requirement. Imaging of line emission from protoplanetary disks at such high resolution requires the full sensitivity of the 60 12-meter antennas; with them, ALMA’s ability to study the internal kinematics of disks would be unequalled by any other instrument. The third Primary Scientific Requirement is to achieve the highest quality imaging in the millimeter and submillimeter bands, to match the quality of images from HST and ground-based adaptive optics. This too is highly sensitive to the number of antennas. It is already a challenge to achieve the Primary (“Level 1”) Scientific Requirements with 60 operating 12-meter antennas. While a smaller number of antennas, such as 50, would not necessarily preclude the primary goals, these groundbreaking programs would require significantly longer integration times and some science objectives could be put at risk due to systematic errors. Dropping to significantly fewer than 50 operating antennas, for example, 40 antennas, is more serious. At 40 operating antennas, the observing time to reach a given sensitivity increases by a factor of 2.3 over the 60-element array. Such an array would also require a different operational model involving multiconfiguration observations to complete key programs, longer projects with increased costs per project, and would hinder the study of large samples of objects in the Level 1 category. ALMA will be the premier instrument in its wavelength regime for two or more generations to come, the millimeter and submillimeter counterpart to the Very Large Array. While mindful of the fixed resources of the current project, the ASAC strongly urges the ALMA Project to consider any methods possible to eventually attain the original goal of 60 operating antennas. 

Charge 2 to the ASAC concerned the issue of how to encourage collaboration through the individual partners of the ALMA project, and the scheduling of large programs in a way that would maximize the scientific productivity of the ALMA instrument given the requirement that the individual partners will have separate Program Review Committees (PRCs). There is a consensus within the Committee that there is some requirement for an International Program Review Committee to consider joint proposals, particularly very large proposals. However the scope of such an IPRC is not immediately clear. The Committee feels that further consideration of this issue is warranted.

Sep2004
8 Summary Points 
• We conclude that the loss or reduction of any element of the baseline pro ject will result in a significant loss of ALMA science (Charge 1). In particular, 
– both observing time for reaching a given sensitivity, and image fidelity scale with the 
square of the number of antennas, so any significant reduction of the number (by more 
than 10%) would result in a significant erosion of ALMA’s discovery space. 
– all receiver bands of the baseline pro ject are vital to important science that would be 
lost if a band was cut entirely. 
– the long baselines are essential for reaching the ma jor science goals of ALMA, among 
them imaging planetary formation in protostellar disks. 
• We recommend that all saving options such as delaying early science operations, or delaying  or reducing other less critical science capabilities should be considered in the context of the enhanced pro ject (Charge 1). 
• We conclude that a time allocation policy which wants to facilitate joint pro jects between partners, and to allow for large or legacy pro jects while avoiding scientific duplication, has to involve a time allocation committee common to all partners (Charge 2). 
• Relaxing the amplitude calibration requirements to 3% below and 5% above 300 GHz does not incur loss of ma jor science goals of ALMA (Charge 3). 
• Demonstration science, with a goal of involving a large part of the astronomical community, would best be performed by joint teams of representatives from this community, and experts from the ALMA science team. These teams would execute a pro ject from defining the observing procedures all the way through publication of the results (Charge 4). 
• We recommend that demonstration science, and early science after that, should not be started too soon, and that a careful management of the expectations is needed, since the early ALMA will have a performance very far from the final observatory (Charge 4). 
• We perceived the science verification plan as being moving into the right direction, but were concerned about sufficient scientific manpower to work out the necessary details in a timely manner, and about the short time allocated to it (Charge 5). 
• We highly recommend that the science verification activities are ramped up a soon as possible(Charge 5).

Summary of Main Recommendations May 2004
The ASAC recommends that the currently proposed technical requirements for delay errors of 22 fsec max rms change in 300 sec (drift) and 65 fsec rms deviation from 10 sec average (noise), proposed by the Systems IPT be adopted for ALMA. This strict technical requirement is important to maximizing ALMA sensitivity at the highest frequencies, which enables major ALMA science goals  (Charge 1).
The ASAC recommends that the project investigate whether there are useful tradeoffs between gain stability and sensitivity that could be made for the four total power antennas. The ASAC also recommends that this issue of gain stability be revisited when the systems group has been able to perform well-controlled and consistent measurements on the ALMA prototype cartridges in the ALMA cryostat  (Charge 1).
The understanding of flow down from calibration accuracy to science loss requires continued study.  The ASAC recommends that theScience IPT identify and study the impact of calibration on a handful of the most challenging major science goals (Charge 2).
The ASAC strongly encourages continued testing of calibration mechanisms to determine if any can provide the project's required level of accuracy. The overall area of absolution calibration needs dedicated effort within the project (Charge 2).
The project should plan for phase calibrator surveys with the ATF and ALMA; the project should also make maximal use of parallel efforts at the IRAM 30-m, CARMA, JCMT, APEX, and PdB. The ATF and ALMA efforts must focussed in the essential needs and not interfere with commissioning and testing (Charge 2).
ALMA must have high angular resolution and high frequencies during Early Science to make significant and unique science impact. This is where the early instrument can make ground-breaking contributions (Charge 3).
The ASAC highly recommends that ALMA plan for science demonstration projects which are released to be the public immediately. These projects should have significant and broad value to the community and the general public; the data would be released with no proprietary period to foster community knowledge of ALMA's capabilities (Charge 3).
 The Operations Plan is off to a good start and will be of high value in directing the project. We agree with the underlying assumptions for the Early Science Operations but much detailed work remains to be done in this area. We hope that the ASAC will be asked for additional input into the time allocation policy (Charge 4).
The ASAC shares the project's concern that the funding ramp up for science operations is not sufficient to be ready for commissioning, science verification and early operations (Charge 4).
It is critical that the core data reduction software be ready for early science. Work toward this goal needs to be monitored and sufficient time should be allowed  for software commissioning.  Failure to have science quality user-friendly software will jeopardize the early credibility of the project in the community at large (Charge 5).
We recommend that the ASAC be asked to re-examine the prioritization of Software Requirement after the operations plan for early science and the software requirement considerations have gone through their next step (Charge 5).
ALMA needs to carefully manage community expectations and science production during the first couple years of early science. The current schedule appears very aggressive and the capabilities of the early array will not be outstandingly superior to concurrent arrays and large telescopes. Time allocations and array scheduling need to be designed to maximize science while minimize negative impact on construction. If the Board has the goal of creating dramatic scientific results during initial early operations, it will be essential utilize the full set of early array configurations and submillimeter frequencies.

5 Summary of Recommendations October 2003
In summary, the ASAC recommends that: 
1. the Project resource, as quickly as possible, the design, construction and testing of the dual-load calibration scheme; 
2. the Project complete the tests of the semi-transparent vane calibration scheme; 
3. the Project continue to aim for the highest possible specification on amplitude repeatability, retaining the current goals of 1% and 3%;  
4. the Project define its strategy to solve the problem of total power imaging, or significant areas of science will be severely compromised or possibly ruled out altogether; 
5. the Front End IPT carry out receiver detuning tests immediately, to see how much improvement in front-end stability can be obtained; 
6. the Front End IPT re-introduce the specification on the allowable differential gain between polarisations to allow ALMA to measure polarisation accurately; 
7. the Front End IPT make the measurements of differential gain stability between the two polarisation channels on a representative receiver prototype 
8. the Science IPT conduct detailed simulations which allow the effect of receiver stability on polarisation measurements to be quantified; 
9. ALMA should keep open the option of allowing P.I. instruments on a small number of antennas at a time, allowing, for example, interferometry at frequencies not covered by ALMA (e.g. > 1 THz) 
10. a procedure is established to allow groups to submit proposals for P.I. experiments, which would have to be reviewed scientifically and technically for their impact on array operations; 
11. a document similar to the DRSP, but much smaller, be prepared which covers typical proposals expected during interim science from 2007-2102.

Apr2003 Recs need to be extracted.
ASAC reaffirms the goals for absolute calibration of ALMA data of 1% and 3% for frequencies below or above 300 GHz respectively.  The ASAC recommends that the Sci IPT include a more detailed drafting of amplitude calibration gols as a function of frequency (including within a band) in the Calibration Plan.
ASAC recommends that development of both the semitransparent vand and the subreflector dual load calibration schemes be abandoned in favor of a scheme using ambient and hot loads.  The ASAC recommends that the calibration group develop the necessary prototype hardware for the loads and a proof-of-principle mechanical design for the calibration widget space.  Amplitude calibration is the highest priority issue in calibration and the ASAC notes that the proposed two-load design has an impact on the Front End IPT.
The ASAC recommends that the detailed simulation of the fast switching and WVR experiments being pursued by the Sci IPT be continued and expanded.  These simulations are required to validate the assumption that the combination of fast switching and 183 GHz water vapor radiometry will provide enough information to phase calibrate the array.
The ASAC recommends that the Project provide additional resources to the Science IPT in the very near term to ensure that a feasible and adequate calibration plan is created.
The ASAC recommends that the project evaluate the role of the ALMA Test Facility (ATF) in validating ALMA's calibration strategy and consider its impact on the resources allocated to the Sci IPT and Antenna Evaluation Group.  In particular, the ASAC recommends that every effort be made to enable interferometric tests of the radiometers on the ATF in winter of 2004/2005.
The ASAC is pleased to find that a trade-off in performance between maximum resolution and intermediate configurations is not required to design the Y_ array.  The ASAC recommends that the configuration team consider whether additional antennas could be placed near the eastern edge of Pampa La Bola and whether the design of the Y+ array can be optimized further by assuming that most projects will combine data from the 4.5 km and Y+ arrays.
The ASAC reiterates its recent recommendation to implement the proposed enhancement to the baseline correlator within the baseline ALMA project.  The ASAC further recommends that the design keep open the possibility of reconfiguring the number of subbands used for a given observation.  The ASAC also recommends that the Correlator IPT simulate the effects of aliasing at band edges and that the Science and Software Requirements (SSR) working group review the possibility of increasing the specification for the average ALMA data rate.
The ASAC reconfirms that the specification for the total power stability for continuum single dish observations is 10-4 in 1 sec.  The specification for gain stability for differential polarization should be 5 10-4 over timescales of minutes for millimeter wavelengths at which a posteriori calibration can be used.  The specification for the gain staiblity for interferometer observations should be 2 10-3 over timescales of minutes for millimeter wavelengths.
The ASAC is very concerned by the preliminary reports that the total power stability may be exceeded by a large factor.  In addition, further work is needed to determine the required gain stability for submillimeter wavelengths, where there are no strong sources to use to measure the gains with 3% accuracy in a short time.  The ASAC recommends that the Science IPT carry out simulations to quantify the science losses (particularly in the areas of wide field continuum imaging, polarization and submillimeter calibration) and to quantify the stability requirements for submillimeter calibration.
The ASAC recommends that the Front End specifications document include a requirement on the phase stability when switching between different receivers.  Such a requirement is essntial for fast-switching observations, which require that phase can be translated accurately from 90 GHz (Band 3) to the target frequency.  The Systems Engineering IPT should investigate whether this phse stability requirement impacts specifications for other astpects of the ALMA system.
The ASAC recommends that Phase III of the IRAM AIPS++ tests(benchmarking) be finished rapidly, with careful attention paid to where time is spent in the different processing steps in the two packages.  The Phase III test should also include testing with full-sized ALMA datasets.
AIPS++ audit last year).  In this context, the ASAC notes that the Pipeline is a particularly critical and highly visible part of the ALMA software which depends on AIPS++.
The ASAC recommends close monitoring of the progress of the planned AIPS++ review as well as AIPS++ progress in completing missing ALMA Software requirements (identified in the 
THE ASAC strongly recommends that a single antenna design be adopted for ALMA.  The ASAC recommends that the project review the antenna specifications to see whether additional specifications would be required to enforce consistency between two different antenna designs.  If two different designs are adopted the ASAC recommends that the identical quadrupod design be used for both antennas, which should help to minimize the impact of the different designs on science.  If two substantially different antenna designs are adopted, the biggest potential impact on the science capabilities of ALMA will be in the areas of polarization observations and wide field mosaics.  In a worst case scenario, imaging of any surces larger than the roughly 1/4 of the ALMA primary beam could be adversely affected.