Doc 10.2, ver. 1.2 | April 26, 2023

ALMA Cycle 10 Proposer’s Guide

ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC(Canada), MOST and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile.
The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ.

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Revision History
Version Date

Editors

1.0
1.1
1.2

George Privon, David Rebolledo, Gergö Popping, Takuma Izumi
George Privon, David Rebolledo, Gergö Popping, Takuma Izumi
George Privon, David Rebolledo, Gergö Popping, Takuma Izumi

2023-04-06
2023-04-18
2023-04-26

In publications, please refer to this document as
G. Privon, et al. 2023, ALMA Proposer’s Guide, ALMA Doc. 10.2, ver. 1.2, 10.5281/zenodo.4511961

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Contents
1 What’s new in Cycle 10
1.1 Technical and observing capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2 Proposal review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2.1 Joint Proposals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2.2 Distributed peer review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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2 ALMA overview
2.1 The ALMA partnership . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2 The ALMA telescope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3 The Joint ALMA Observatory and the ALMA Regional Centers . . . . . . . . . . . . . . . . . .
2.4 The ALMA Science Portal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.5 ALMA proposal eligibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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3 Proposal types
3.1 Regular proposals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2 Target of Opportunity proposals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3 Large Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4 mm-VLBI and Phased Array proposals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.5 Joint Proposals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.5.1 ALMA proposals requesting JWST time . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.5.2 ALMA proposals requesting VLA time . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.5.3 ALMA proposals requesting VLT time . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.6 Director’s Discretionary Time proposals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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4 Proposal planning
4.1 Time available in Cycle 10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2 Summary of capabilities offered in Cycle 10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3 Scheduling considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3.1 Weather . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3.2 Angular resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3.3 Configuration schedule for the 12-m Array . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3.4 Observing pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.4 Duplicate observations and resubmissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.4.1 Checking for duplications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.4.2 Resubmission of an unfinished proposal . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.5 Estimated observing time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.6 Supporting tools and documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.6.1 The Observing Tool documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.6.2 Additional proposal preparation tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.6.3 The ALMA Regional Center guides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.6.4 Supplemental documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.7 The ALMA Helpdesk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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5 Proposal preparation, submission, and review
5.1 Proposal format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2 Dual-Anonymous proposal review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3 Preparing the Scientific Justification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3.1 Page limits and fonts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3.2 Science case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3.3 Figures, tables, and references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.4 Preparing the Technical Justification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.5 Management Plan for Large Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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5.6

Proposal validation, submission and withdrawal . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.6.1 Proposal updates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Proposal evaluation and selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.7.1 Peer review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.7.2 Evaluation criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.7.3 Proposal selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Proposal confidentiality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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6 Post-proposal activities
6.1 Observation preparation and submission: Phase 2 . . . . . . . . . . . . . . . . . . . . . . . . . .
6.2 Changes to submitted programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.3 Data processing and data delivery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.4 Opportunities for public promotion of ALMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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A ALMA Cycle 10 Capabilities

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B Technical Justification guidelines

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C Acronyms and abbreviations

59

D Science categories and keywords

61

5.7

5.8

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List of Figures
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3
4
5
6

Cycle 9 proposal length and acceptance rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Historical Monthly PWV Percentiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Time available per band based on historical monthly PWV measurements . . . . . . . . . . . . .
Time available per band based on analysis of phase RMS . . . . . . . . . . . . . . . . . . . . . .
Estimated available observing time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cycle 9 estimated execution time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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List of Tables
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2
3
A-1
A-2
A-3
A-4
A-5
A-6
A-7
A-8
A-9

The ALMA Cycle 10 timeline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Joint Proposal Time Caps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Planned 12-m Array Configuration Schedule for Cycle 10 . . . . . . . . . . . . . . . . . . . . . . 21
Angular Resolutions (AR) and Maximum Recoverable Scales (MRS) for the Cycle 10 configurations 36
Allowed Array Combinations and Time Multipliers . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Properties of ALMA Cycle 10 Receiver Bands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Properties of ALMA Cycle 10 Correlator Modes, dual-polarization operation . . . . . . . . . . . 40
Default frequencies for Continuum Polarization Observations . . . . . . . . . . . . . . . . . . . . 42
Maximum separation angle between phase calibrator and science target . . . . . . . . . . . . . . 46
Time cadence of images obtained with FRM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Observing frequencies for Cycle 10 solar observations . . . . . . . . . . . . . . . . . . . . . . . . . 48
Default observing frequencies for Cycle 10 VLBI Observations . . . . . . . . . . . . . . . . . . . . 50

5Cycle 10 Call for Proposals
The ALMA Director, on behalf of the Joint ALMA Observatory (JAO) and the partner organizations in East
Asia, Europe, and North America, is pleased to announce the ALMA Cycle 10 Call for Proposals (CfP) for
scientific observations to be scheduled from October 2023 to September 2024. We encourage interested parties
to follow the ALMA Science Portal for the latest information.
The JAO anticipates allocating 4300 hours on the 12-m Array and 4300 hours on the Atacama Compact Array(ACA), also known as the Morita Array, for successful proposals in Cycle 10. The ACA allocation includes
4300 hours each on the 7-m Array and the Total Power (TP) Array. Proposals must be prepared and submittedusing the ALMA Observing Tool (ALMA OT), which is available for download from the ALMA Science Portal(www.almascience.org).
Proposal reviews will be conducted via a dual-anonymous process. While proposers will still enter their names
and affiliations in the ALMA OT, their identities will be concealed from the science reviewers. It will be theresponsibility of the investigators to write their proposals such that anonymity is preserved. In addition, ALMA
is using distributed peer review for proposals requesting less than 50 hours on the 12-m Array and for ACA
stand-alone proposals requesting less than 150 hours on the 7-m Array. The PI for such proposals or a designee
from the list of investigators will review and rank 10 submitted proposals from this Call, for each proposal
submitted.
ALMA Cycle 10 proposal submission will open at 15:00 UT on Wednesday, 12 April 2023. The Cycle 10
proposal submission deadline is 15:00 UT on Wednesday, 10 May 2023. These and other importantmilestones for Cycle 10 are summarized in Table 1. PIs are responsible for submitting their proposals successfullyby the deadline, and are strongly advised to submit proposals early.
Cycle 10 will not include a Supplemental CfP for stand-alone ACA observations. The community is encouraged
to submit ACA projects, especially in the LST range of 20h to 10h, for the May 2023 deadline.
ALMA provides continuum and spectral-line capabilities for wavelengths from 0.32 mm to 8.5 mm, and angularresolutions from 0.008800 to 8.500 on the 12-m Array. In Cycle 10, the following configuration and observing
band combinations will be offered for the 12-m Array: configurations C-1 through C-8 for Bands 3 through10. These combinations will provide angular resolutions as fine as 0.01100 . Band 1 observations are expected
to start in March 2024 and will be available in configurations C-1 through C-6. Cycle 10 will bring several
new observational capabilities to ALMA, including Band 1 observations with the 12-m Array, spectral scansincluding Total Power observations, 4x4 bit spectral modes, Solar observations with full-polarization in Band 3,
and expanded VLBI and Phased array capabilities. Proposals with observations in the highest-frequency Bands
8, 9, and 10 are strongly encouraged.
This Proposer’s Guide provides an overview of significant changes since Cycle 9 made in both the technical capabilities and observing strategies (Section 1), an overview of the ALMA organization (Section 2), the proposal
types offered in Cycle 10 (Section 3), information on proposal planning (Section 4), proposal submission (Section 5) and post-proposal activities (Section 6), an overview of the offered technical capabilities (Appendix A),
and guidelines for writing a Technical Justification (Appendix B).

1What’s new in Cycle 10

This section summarizes significant changes made since Cycle 9. Any changes, clarifications, or bugs that are
discovered after the publication of this Proposer’s Guide will be documented in the Knowledgebase Article:
What Cycle 10 proposal issues and clarifications should I be aware of before submitting my proposal? Proposers
should check this article regularly, especially just before submitting their proposals.

1.1

Technical and observing capabilities

Observing capabilities are given in Appendix A and fully described in the ALMA Cycle 10 Technical Handbook(hereafter, the Technical Handbook). New capabilities in Cycle 10 include:

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Date

Milestone

12 April 2023 (15:00 UT)

Release of Cycle 10 Call for Proposals, Observing Tool, and supporting documents, and opening of the Archive for proposal submission

10 May 2023 (15:00 UT)

Proposal submission deadline for Cycle 10 Call for Proposals

28 June 2023 (15:00 UT)

Deadline to submit reviews for the distributed peer review system

August 2023

Announcement of the outcome of the proposal review process

1 October 2023

Start of ALMA Cycle 10 Science Observations (anticipated)

30 September 2024

End of ALMA Cycle 10
Table 1: The ALMA Cycle 10 timeline• Band 1 on the 12-m Array. Observations will be available for Stokes I only (no Stokes Q/U/V) andare anticipated to be available from March 2024. Band 1 will not be available in configurations C-7 andC-8.
• Spectral scans that include Total Power observations.
• 4x4-bit spectral mode for improved sensitivity on the 12-m Array (dual polarization). 4x4
mode significantly reduces the time required for specific spectral-line observations. However, 4x4 mode is
not recommended for continuum observations because it reduces the available bandwidth, compared tothe standard 2x2 bit mode (see Section A.6.1).
• Solar observations in full polarization in Band 3 using only the 12-m Array.
• Phased array mode in Bands 1, 3, 6 and 7. The total time available for this mode will be limited
to 50 hours.
• Continuum and spectral line VLBI in Bands 1, 3, 6 and 7, including flexible tuning.

1.2

Proposal review

1.2.1

Joint Proposals

With the aim of exploiting the synergies between ALMA and other major facilities, the JAO has entered into
an agreement with The Space Telescope Science Institute (STScI), The National Radio Astronomy Observatory(NRAO), and The European Southern Observatory (ESO) to provide support for Joint Proposals with theJames Webb Space Telescope (JWST), the Very Large Array (VLA), and the Very Large Telescope (VLT),
respectively. Joint Proposals will be multi-wavelength and/or multi-observatory in nature, and will have tobe scientifically justified and explicitly specified as Joint Proposals in the ALMA OT. Further details on Joint
Proposal opportunities are provided in Section 3.5.
1.2.2

Distributed peer review

In Cycle 10, reviewers participating in distributed peer review can be assigned a maximum of five Proposal Sets
(i.e., 50 proposals). Thus, PIs who are planning to submit multiple proposals are encouraged to designate oneof their Co-Is as reviewer. More information is provided in Section 5.7.1.
Additionally, in Cycle 10, if a reviewer needs to contact the ALMA Proposal Handling Team (PHT) during the
proposal review process, they should do so by opening an ALMA Helpdesk ticket (with the "Proposal Review
Support" department) instead of using the PHT email.

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2

ALMA overview

2.1

The ALMA partnership

ALMA, an international astronomy facility, is a partnership of the European Organisation for Astronomical
Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National
Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA operations
are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO),
managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical
Observatory of Japan (NAOJ) on behalf of East Asia. JAO provides the unified leadership and management of
the commissioning and operation of ALMA.

2.2

The ALMA telescope

ALMA contains 66 high-precision antennas. Fifty of these are 12-meter dishes in the 12-m Array, used forsensitive, high-resolution imaging. The remaining sixteen make up the ACA, used to enhance wide-field imaging: twelve are closely spaced 7-meter antennas (7-m Array), and four are 12-meter antennas for single-dishobservations (Total Power Array or TP Array). The wavelengths covered by ALMA range from 0.32 mm to
8.5 mm (frequency coverage of 35 GHz to 950 GHz).
The Array is located on the Chajnantor plateau of the Chilean Andes at latitude = −23.029◦ , longitude = −67.755◦
and an altitude of 5000 m. The site (referred to as the Array Operations Site, AOS) offers the exceptionallydry and clear sky conditions required to operate at millimeter and submillimeter wavelengths. The AOS isconnected via gigabit fiber links to the Operation Support Facility (OSF), located at an altitude of 2900 m
and 40 km from the town of San Pedro de Atacama. Science operations are conducted from the OSF and the
JAO Santiago Central Office (SCO).
The Technical Handbook contains a detailed description of the ALMA technical characteristics.

2.3

The Joint ALMA Observatory and the ALMA Regional Centers

The JAO is responsible for the overall leadership and management of ALMA operations in Chile. The JAO
solicits proposals to observe with ALMA through Calls for Proposals and organizes the peer review of the
proposals by science experts. In addition, the JAO schedules all science observations and places the data in theelectronically accessible Archive.
The three Executives maintain the ALMA Regional Centers (ARCs) within their respective regions. The ARCs
provide the interface between the ALMA Observatory and its user communities. The ARCs are responsible foruser support, mainly in the areas of proposal preparation, observation preparation, acquisition of data throughthe Archive, data reduction, data analysis, data delivery, face-to-face visitor support and workshops, tutorials,
and schools. Each ARC operates an archive that mirrors the SCO Archive. Browsing and data mining are done
through the ARC mirror archives.
The East Asian ARC (EA ARC) is based at the National Astronomical Observatory of Japan (NAOJ) headquarters in Tokyo. It is operated in collaboration with Academia Sinica Institute of Astronomy and Astrophysics(ASIAA) in Taiwan and Korea Astronomy and Space Science Institute (KASI) in Korea and supports theastronomical communities of Japan, Taiwan1 and the Republic of Korea.
European researchers are supported by the European ARC (EU ARC), which is organized as a coordinatednetwork of scientific support nodes distributed across Europe. The EU ARC is located at ESO Headquarters
in Garching bei München (Germany), where many of the ARC activities take place. Face-to-face support andadditional services are provided by seven regional nodes. The regional nodes are currently: Bonn-Cologne(Germany), Bologna (Italy), Onsala (Sweden), IRAM, Grenoble (France), Allegro, Leiden (The Netherlands),
Manchester (United Kingdom) and Ondřejov (Czech Republic).
The North American ARC (NA ARC) is contained within the North American ALMA Science Center (NAASC),
1 Support of the Taiwanese astronomical community is shared by the EA and NA ARCs.

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based at NRAO headquarters in Charlottesville, VA, USA. It is operated in collaboration with the National
Research Council of Canada (Canada) and Academia Sinica Institute of Astronomy and Astrophysics (Taiwan),and supports the astronomical communities of North America and Taiwan2 .

2.4

The ALMA Science Portal

The ALMA Science Portal (SP), accessible at http: // almascience. org , is the primary access point to
ALMA for science users. It provides a gateway to all ALMA resources, documents and tools relevant to users
for proposal preparation, proposal assessment, project tracking, project data access and data retrieval, as wellas access to the ALMA Helpdesk.
From the Science Portal, anyone can:• Register as an ALMA user.
• Access ALMA user documentation and software tools, including the ALMA Sensitivity Calculator, observing simulators, and the ALMA spectral-line database (Splatalogue).
• Download the ALMA OT.
• Access Helpdesk “Knowledgebase” articles, which provide answers to common questions.
• Access non-proprietary data from the ALMA Archive.
In addition, registered users may:
• Manage their user profile. Here, users can specify their area of expertise and conflicts of interest, set
an option to receive automatic email notifications of the progress of their observations, grant access toproprietary data for other ALMA users, and delegate the right to trigger Target of Opportunity (ToO)
observations to another selected ALMA user.
• Access SnooPI, the tool for PIs, Co-PIs, Co-Is, and any other user designated by the PIs, to monitor the
status of their scheduled observing projects.
• Submit Helpdesk tickets.
• Trigger ToO observations.
• Access their proprietary data through the ALMA Archive.
The Science Portal also includes links to the ARC’s webpages, from which users can access regional informationand specific services of each ARC. This includes visitor and student programs, schools, workshops, and outreachmaterials and activities.
Users must update their ALMA user profile, rather than registering multiple accounts, whenever there is achange in their personal information such as a new email address or a change of affiliation (see the ALMA
Users’ Policies). Users are encouraged to complete the “Demographics” section of their profile to help ALMA
provide adequate user support and also to select keywords corresponding to their scientific expertise to help
with distributed peer review (Section 5.7.1).

2.5

ALMA proposal eligibility

Users of any nationality or affiliation may submit an ALMA proposal. All proposals are evaluated on the basisof scientific merit by a distributed peer review system or by a panel-based proposal review system.
Each proposal must have a PI who is the official contact between ALMA and the proposing team for all
correspondence related to the project. Large Programs proposals may designate Co-PIs, who will share theoverall responsibility of conducting the proposed science. If Co-PIs are identified, the requested observing time
will be split among the regions (North America, Europe, East Asia, and Chile) in proportion to the affiliationsof the PI and Co-PIs (see Section 5.7.3).
Regardless of the inclusion of Co-PIs, the PI has proprietary access to the ALMA data during the proprietary
period, and is in charge of the delivery of the value-added data products in the case of Large Programs, in

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0.5

Cycle 9 proposal success rate

Number of submitted proposals

200

150

100

50

0

0

10

20

30

40

Estimated 12-m Array execution time [h]

50

0.4

0.3

0.2

0.1

0.0

Large
Programs

0

10

20

30

40

50

Estimated 12-m Array execution time [h]LargePrograms

Figure 1: (Left) Number of proposals submitted as a function of the 12-m Array execution time in Cycle 9.
(Right) The fraction of proposals (with 1σ confidence intervals) that were assigned priority Grade A or B as afunction of the estimated 12-m Array time.
accordance with the ALMA Users’ Policies. Any other individuals who are actively involved in any proposal
may be designated as Co-Is. There is no limit to the number of Co-Is or Co-PIs who may appear on a proposal.
Additional rules apply for qualification to use the Chilean share of the time and they are described at:
http://www.das.uchile.cl/~alma_crc/ .
ALMA Users’ Policies prohibit multiple submissions of the same proposal using different regional affiliations. If
such proposals are detected, only the first submitted version will be considered by the reviewers.

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Proposal types

3.1

Regular proposals

Regular proposals relate to observations that can be fully specified by the proposal submission deadline andwhose estimated execution time does not exceed 50 hours on the 12-m Array or 150 hours on the 7-m Array instand-alone mode. Regular proposals may involve time-critical, multiple-epoch observations, and the monitoringof a target over a fixed time interval.
The JAO aims to have a diverse scientific portfolio by executing a balance of programs with various sizes interms of observing time. Figure 1 (left panel) shows that most Cycle 9 proposals requested between 2 and 20
hours of 12-m Array time. The success rate of proposals was independent of proposal length up to at least
30 hours of requested 12-m Array time (Figure 1, right panel).
No restrictions are imposed on the size of the time window specified by PIs for time-critical observations (seeSection A.10). The scheduling feasibility of any proposal will depend on the total number of constraints that are
imposed (see Section 4.3). Importantly, any time constraint, as with any other type of observational constraint,
must be scientifically and technically justified.

3.2

Target of Opportunity proposals

Target of Opportunity (ToO) proposals should be submitted for observations that can be anticipated but whosetargets and/or time of observation are not known in advance. Like Regular proposals, these proposals mustbe submitted by the Cycle 10 proposal deadline. As for all other types of proposals, observing modes andsensitivity requests must be specified at the time of submission. In contrast, the target list may be specified at
the moment of triggering the proposal. For each triggered Scheduling Block (SB) the proposal should specify
the number of triggers needed, what the trigger event will be, and the necessary reaction time for schedulingthe observation after it is triggered. Regular proposals wrongly submitted by the PI as ToO proposals may be10

rejected on technical grounds.
The JAO will give priority to observing ToO proposals during the time period requested by the PI aftera trigger request has been submitted, provided the appropriate scheduling conditions (mainly weather andantenna configuration, see Section 4.3) are met and the observations do not conflict with critical engineeringand development activities or critical observations with a higher grade. For requests of reaction times under
24 hours, PIs are recommended to give notice as early as possible about target coordinates or redshift for
preparation of the Phase 2 SBs. PIs will trigger observations from accepted ToO proposals through the Project
Trigger Submission Page available at the ALMA Helpdesk. Further instructions on how to trigger a project
are available at the ToO Activation page on the Science Portal. Upon receiving a trigger, the Observatory willcommunicate with the PI through the Helpdesk ticket to clarify any remaining issues.

3.3

Large Programs

Large Programs are proposals with an estimated execution time of greater than 50 hours on the 12-m Array (withor without accompanying ACA time) or 150 hours on the 7-m Array in stand-alone mode. Large Programs should
not involve time-critical or ToO observations, and may not include observations in Band 1, full polarization
measurements, solar observations, VLBI, Phased Array mode, Astrometric observations (see Section A.9.5) or
observations requiring band-to-band calibration or bandwidth switching calibration (see Section A.9.6). Large
Programs may fill up to 50% of the available time for a given LST range in the available Cycle 10 configurations(i.e., the ACA and C-1 through C-8). Section 4.3.3 shows the configuration schedule and time available perconfiguration.
A Large Program proposal should address strategic scientific issues that will lead to a major advance or breakthrough in the field, be a coherent science project and not reproducible by a combination of Regular proposals,
lead to value-added data products, and contain a solid management plan ensuring an efficient utilization of
the data. Consequently, the proposal team should not submit one or more Regular proposals for the sameobservations in parallel with a Large Program. In such a case, the Regular proposals would not be considered.
Further details are available in the Knowledgebase article “Are there policies specific to Large Programs?”.
Large Program teams are expected to deliver their proposed value-added data products and documentation
describing the data products to ALMA within one year of the final delivery of calibrated products. The valueadded data products and documents will be made available to the community at large. The Science Portal
contains a document describing the standards for Large Program enhanced products to ensure their proper
ingestion into the ALMA Science Archive.

3.4

mm-VLBI and Phased Array proposals

ALMA VLBI proposals may be made in concert with the Global Millimeter VLBI Array (GMVA) at 7 mm
(Band 1) or 3 mm (Band 3) or with the Event Horizon Telescope (EHT) network at 1.3 mm (Band 6) or
0.87 mm (Band 7). For all Cycle 10 7 mm and 3 mm VLBI observations, PIs must have submitted a proposal
to the GMVA network by 1 February 2023 in addition to their ALMA VLBI proposal.
ALMA-specific VLBI considerations are given in Section A.12 of this document. Further details on submitting
7 mm and 3 mm VLBI proposals to the GMVA are available from the GMVA website. Further details on
submitting 1.3 mm and 0.87 mm VLBI proposals using the EHT are available from the EHT website.
VLBI proposals should include a quantitative justification describing why ALMA is essential for the project.
VLBI observations cannot be included in Large Programs. VLBI observations for Cycle 10 that include ALMA
will likely be carried out in March/April 2024.
Approved VLBI projects that are not executed or that result in failed observations will not be carried overto the next cycle. Given that the outcome of Cycle 9 VLBI proposals may not be known before the ALMA
Cycle 10 proposal deadline, PIs of such proposals may wish to resubmit their proposals in Cycle 10 in case the
Cycle 9 observations are unsuccessful. No resubmission to the GMVA call for proposals is needed in such cases.
Further details on the handling of resubmitted proposals are available in Section 4.4.2.
Pulsar observing capabilities using ALMA’s Phased Array observing mode are described in Section A.13 of this11

document. A maximum of 50 hours of Cycle 10 time will be available for Phased Array mode observations.
These observations will take place during the VLBI time blocks, anticipated to be in March/April 2024. Phased
Array observations cannot be included in Large Programs.

3.5

Joint Proposals

Proposals can be submitted jointly with ALMA and the partner facilities: JWST, VLA, and VLT. Proposers
can submit a Joint Proposal to ALMA that also requests time on any or all of the partner facilities or submit a
proposal to one of JWST, VLA, or VLT that requests ALMA time. The intent of Joint Proposals is to facilitate
programs that require observations from multiple facilities to achieve the stated science aims, and the need forthe requested data must be described in the Scientific Justification. Joint Proposals will follow the users’ policies
and call for proposals guidelines of each of the requested partner observatories, as well as the extra limitations
and rules imposed on Joint Proposals by each observatory. Joint proposals must be explicitly specified as suchin the ALMA OT and in the submission tools of the partner observatories.
PIs must submit their Joint Proposals to the observatory that requires the most observing time. In the caseof ALMA, the relevant time request will be the amount of time requested for the 12-m Array, or the 7-m
Array in case of ACA stand-alone proposals. In Joint Proposals, ALMA is the "Main" observatory if it is
the observatory with the largest time request, otherwise ALMA is the "Partner" observatory. The same Joint
Proposal cannot be submitted to multiple observatories, i.e., a submitted proposal cannot be under review byanother observatory. Both ALMA and the partner observatories reserve the right to identify and reject suchduplicate submissions.
By agreement, each partner observatory will allow ALMA to allocate time on their telescopes for Joint Proposals
submitted to ALMA: STScI will allow ALMA to allocate up to 115 hours of JWST time; NRAO will allow
ALMA to allocate up to 5% of the available time on the VLA; and ESO will allow ALMA to allocate up to 50
hours of VLT time. Similarly, ALMA will allocate 115 hours, 50 hours, and 50 hours for proposals submitted to
JWST, VLA, and VLT, respectively on each of the Arrays (12-m, 7-m, and TP). These allowed time allocations
are summarized in Table 2.
PartnerMaximum time ALMA can allocate
on partner observatory

Maximum time partner observatory
can allocate on each ALMA array

JWST

115 hours

115 hours

VLA

5% of available time

50 hours

VLT

50 hours

50 hours

Table 2: Amount of time that can be allocated by ALMA on partner observatories and the amount of timethat can be allocated by partner observatories on each ALMA array (i.e., 12-m, 7-m, and TP).
When ALMA is the Main observatory in a Joint Proposal there are no restrictions regarding the observing modes.
However, a Joint Proposal in which ALMA is a partner observatory cannot request ALMA time for VLBI or
Phased Array observing modes. Requests for ALMA Large Programs are not allowed for Joint Proposals when
ALMA is a partner observatory, and therefore the amount of ALMA time requested must be less than that of the
ALMA Large Program threshold (see Section 3.3). Limits to the amount of time requested by a single proposal
will be defined by each observatory. Time constrained or Target of Opportunity observations will be allowed
and should take into account the scheduling limitations and offered response time of each of the observatories
involved. The PI will be responsible for triggering observations at each observatory, following the procedures
specified by the individual observatories. Any requirement regarding simultaneous or coordinated observations
will need to be clearly stated in the proposal, and its feasibility will be evaluated by all observatories.
PIs are responsible for providing the technical justification for each of the observatories according to the guidelines provided below. All Joint Proposals will be assessed technically by each of the requested observatories
based on the information provided by the PI and, after acceptance, during the preparation of the observations.

12Each observatory will follow their technical criteria for acceptance. ALMA projects will be evaluated based on
the technical feasibility of the requested observations, the scheduling feasibility considering the requested array
configuration and any time constraints specified in the proposal. Joint Proposals where ALMA is the Mainobservatory will be rejected in their entirety if deemed technically infeasible by any of the partner observatories. When ALMA is the partner observatory, the ALMA observations will be canceled if any of the involved
observatories declares the proposal technically infeasible.
Joint Proposals accepted by ALMA will be assigned Grade A; they will have high observing priority and willremain in the queue for a period of up to two years. Upon acceptance of a Joint Proposal by ALMA, the PIsof the corresponding proposal will be contacted to proceed with project preparation prior to observations at
the requested partner observatories. Project IDs for the individual partner observatories will be generated only
after acceptance of a Joint Proposal.
Major change requests after a project has been accepted will have to be submitted to the Main observatory.
This includes changes in the time constraints of simultaneous/coordinated observations. Minor changes can besubmitted to the observatory where the change is required. The definition of major and minor change request
is provided by each observatory and PIs may be asked to submit a major change request if deemed needed.
3.5.1

ALMA proposals requesting JWST time

Joint proposals requesting JWST time may request standard JWST observing modes. Target of Opportunity(ToO) proposals must state explicitly whether the JWST observations require a disruptive ToO (observations
within 21 days of notification). No more than one (1) disruptive JWST ToO of the joint program will be
performed per JWST Cycle. Furthermore, Ultra-rapid JWST ToO requests (reaction time 2 days or less) will
not be accepted for this program; proposals asking for Ultra-rapid JWST ToO observations must be submitted
in response to the JWST Call for Proposals, with JWST as the primary observatory. It is mandatory that the
PI informs both observatories immediately if the trigger criterion is fulfilled.
Establishing the technical feasibility of the JWST observations is the responsibility of the PI, who should
review the JWST Call for Proposals, JWST Documentation, and/or contact the JWST Helpdesk. The JWST
Helpdesk offers features to search the documentation and to send your question directly to the appropriate
team of experts. Questions may also still be submitted via e-mail to help@stsci.edu. For proposals that areapproved by ALMA, STScI will perform final detailed feasibility checks. STScI reserves the right to reject any
ALMA-approved Joint Proposal observation that proves infeasible, impossible to schedule, and/or dangerous
to the JWST instruments. Any JWST observations that prove infeasible or impossible could jeopardize theoverall science program and may cause revocation of the corresponding ALMA observations. Duplicate JWST
observations may also be rejected by the STScI.
STScI will contact successful PIs of joint programs. US Investigators of ALMA-JWST Programs are eligible forfunding and will be eligible to submit budgets to JWST Grants.
JWST Technical Justification ALMA proposals requesting JWST time must provide a Technical Justification, describing the overall experimental design of the program and justifying the selection of instruments,
modes, exposure times, and any constraints. The Technical Justification must describe how the observations
contribute to the goals described in the scientific justification. Proposals must provide quantitative estimatesof the accuracy required to achieve key science goals. The JWST ETC generally provides sufficient information
to determine the necessary exposure time. For modes that require target acquisition, proposers should verify
that the exposure specifications provided meet the stated criteria for success. Successful target acquisitions are
crucial for the success of the specified observations, and must be verified. The description should also include
the following:• Special Observational Requirements (if any): Justify any special scheduling requirements, including timecritical observations. Target of Opportunity observations should estimate the probability of occurrence
during Cycle 2, specify whether long-term status is requested, identify whether ToOs are disruptive or
ultra-disruptive, and state clearly how soon JWST must begin observing after the formal activation.
• Justification of Coordinated Parallels (if any): Proposals that include coordinated parallel observations
should provide a scientific justification for and description of the parallel observations. It should be clearly13indicated whether the parallel observations are essential to the interpretation of the primary observationsor the science program as a whole, or whether they address partly or completely unrelated issues. The
parallel observations are subject to scientific review, and can be rejected even if the primary observations
are approved.
• Justification of Duplications (if any): as detailed in the JWST Duplicate Observations Policy. Any
duplicate observations must be explicitly justified.
3.5.2

ALMA proposals requesting VLA time

ALMA proposals may request standard VLA observations. Proposers should familiarize themselves with the
Guide to Proposing for the VLA and use the VLA Exposure Calculator when preparing their VLA Technical
Justification.
VLA Technical Justification ALMA proposals requesting VLA time must provide a Technical Justification,
describing the experimental design of the program. This should include:• Justifying the requested array configuration(s) and justifying the required angular resolution and largest
angular scale.
• A description of the frequency selection. If the observations involve spectral lines, the rest frequency or
sky frequency (for lines with significant redshift) should be provided.
• A description of the time request (specifying both the on-source and total time, including overhead).
If multiple array configurations are requested, the time request should be separated by configuration.
The time request should be justified in terms of the required sensitivity and the appropriate observing
bandwidth, describing how the sensitivity is necessary to achieve the science goals and if the resulting
data will be limited by sensitivity or dynamic range.
• A description of the choice of samplers and the correlator set-up(s) requested. For spectral line observations
also provide and justify details such as the channel widths and number of channels per sub-band. For
pulsar binning observations, explain how the number of bins selected is sufficient to achieve the project’s
goals; also verify that the frequency resolution is sufficient to avoid excessive dispersive smearing.
• A description of the observing strategy. If the observations require mosaicking, the Technical Justification
should describe the observing strategy (e.g., pointed, on-the-fly mapping) and the mosaic size. If subarrays are requested, the sub-arrays should be described (e.g., number of sub-arrays, numbers of antennas
in each sub-array, observing setup for each sub-array).
3.5.3

ALMA proposals requesting VLT time

Joint proposals requiring VLT time will comply with the ESO policies and Call for Proposals. Only Service
Mode observations are offered2 for joint proposals.
During the preparation of the proposal, PIs should consult technical information provided on the instrument
webpages and within the user manuals for the instruments3 , consider the Service Mode policies, and use the ESO
Exposure Time Calculators to estimate the requested time and feasibility of their observations. The overheads
webpage provides a summary table of all the overheads that must be included within the total requested time.
A more detailed computation of the required execution time can be obtained by running the demo version of
the web-based Phase 2 tool. PIs must provide a technical justification for the requested VLT observations.
An incomplete Technical Justification may lead to the rejection of the proposal on technical grounds. The
justification will be provided via text box in the ALMA OT and should describe the items listed below and theETC version used for the calculations. VLT projects will be evaluated based on the technical feasibility of therequested observations, the scheduling feasibility, time and observing constraints.
Upon acceptance of a Joint Proposal by ALMA, PIs will be requested to submit the project with the ESO
proposal submission tool. The users will later be contacted to regarding submission of the Phase 2 Observing
2 See https://www.eso.org/sci/observing/phase2/SMPhilosophy.html
3 The most recent news on instrument availability can be found on the ESO period-specific call for proposals. The latest available
ESO call can be accessed via: https://www.eso.org/sci/facilities/lpo/cfp.

14

Blocks in preparation for observations and for a final detailed technical assessment. Projects that, during
preparation of the Observing Blocks, result in a larger observing time than requested in the proposal VLT
Technical Justification are subject to rejection on technical grounds at ESO’s discretion. Once the Observing
Blocks have been prepared, projects will immediately enter the ESO observing queue, unless requesting observing
capabilities only offered in the upcoming Period. In the latter case, the project will enter the queue at thecorresponding Period start date. Approved joint Projects will be allocated time in the A-rank class, and be
subject to the same rules applying to regular programs allocated in this class (see the Section 6.4 of the ESO
Call for Proposals).
VLT Technical Justification The technical justification will be entered into a text box in the ALMA OT
and should include a description of:• The number and type(s) of targets (stars, extended sources, etc.)• The apparent magnitudes of targets in appropriate/relevant filter bands• Instrument(s) and mode(s) requested• Constraints on the observing conditions including, lunar phase, sky transparency, and seeing, with justifications for the constraints (see the ESO Phase 2 Observing conditions: definitions page for additional
information)• Any time critical aspects (e.g., monitoring or requirements for an absolute time window)• Justification for the total observing time request, including all overheads and a description of the parameters used in the ETC.
• Special calibration requests not covered by standard instrument calibration plans

3.6

Director’s Discretionary Time proposals

Director’s Discretionary Time (DDT) proposals may be submitted at any time. To qualify for DDT, proposals
must fulfill the conditions specified on the Science Portal. Capabilities, time tolerance restrictions, and scienceassessment will be based on the same criteria as for Regular and ToO proposals, and DDT proposals mustcomply with the anonymization rules. DDT proposals will be considered for approval by the ALMA Director
based on the advice of a Standing Review Committee, with members from the JAO and the four regions,
appointed by the Executive Directors and the ALMA Director. In exceptional cases, the ALMA Director may
approve DDT proposals that would benefit from a very rapid response, and inform the Standing Committee
and science operations team of this decision within 24 hours. Further DDT policies are described in the ALMA
Users’ Policies.

4

Proposal planning

4.1

Time available in Cycle 10

Cycle 10 will span 12 months, starting in 2023 October and finishing in 2024 September.
The JAO anticipates allocating 4300 hours on each of the 12-m, 7-m, and TP Arrays for successful PI programs,
including DDT proposals as well as Cycle 9 grade A proposals that are carried over. VLBI and DDT projects arelimited to a maximum of 5% each of the available time (Sections 3.4 and 3.6). There is no overall cap on Large
Programs, but they may not fill more than 50% of the time at a given LST (for the ACA and configurations
C-1 through C-8; see Section 3.3).

4.2

Summary of capabilities offered in Cycle 10

The Cycle 10 capabilities are described in Appendix A. In summary, they are:Number of antennas:• At least forty-three antennas in the 12-m Array.

15

• At least ten 7-m antennas (for short baselines) and three 12-m antennas (for single-dish maps) in the
ACA.
Receiver bands:• Receiver Bands 1, 3, 4, 5, 6, 7, 8, 9, and 10 (wavelengths of about 7.0, 3.0, 2.0, 1.6, 1.3, 0.85, 0.65, 0.45,
and 0.35 mm, respectively).
• Band 1 observations will not be offered at the beginning of Cycle 10. It is anticipated that Band 1 scienceobservations will begin in March 2024.
12-m Array Configurations:• Cycle 10 includes configurations C-1 through C-8. Band 1 will only be available for configurations C-1
through C-6.
• Maximum baselines between 0.16 km and 8.5 km depending on array configuration.
Some ALMA subsystems may report configurations of the form “C43-X”; these are equivalent to the “C-X”
configurations described here and in the Technical Handbook. Configurations with maximum baselines
equal to or longer than 3.6 km (i.e., C-7 and C-8, as offered in Cycle 10) are considered “long-baseline
configurations”. Observations in these configurations include more frequent calibration compared to morecompact configurations to ensure the quality of the observations. Files containing notional antenna configurations for the 12-m and 7-m Arrays suitable for Common Astronomy Software Applications (CASA)
simulations are available from the ALMA Science Portal.
Spectral-line, continuum, and mosaic observations:• Spectral-line and continuum observations with the 12-m Array and the 7-m Array in Bands 3 through 10.
Spectral-line and continuum observations in Band 1 will be available only with the 12-m Array.
• Single-field interferometry (Bands 3 to 10) and mosaics (Bands 3 to 9) with the 12-m Array and the 7-m
Array. In Band 1, single-field interferometry and mosaics are only available with the 12-m Array.
• Single-dish spectral-line observations in Bands 3 to 8.
Polarization• Single-pointing, on-axis, full linear and circular polarization for both continuum and full spectral resolution
observations in Bands 3 to 7 on the 12-m Array. The field of view of linear and circular polarization
observations is limited to the inner one third and the inner one tenth of the primary beam, respectively.
The minimum detectable degree of circular polarization is 1.8% of the peak flux for both continuum andfull spectral resolution observations. Polarization observations are not available in Band 1.
• Mosaics for continuum linear polarization observations for the 12-m Array in Bands 3 to 7.
• Single-pointing, on-axis linear polarization on the stand-alone 7-m Array in Bands 3 to 7. The field ofview is limited to the inner one third of the primary beam. A maximum of 75 hours will be offered forthis mode.
Band-to-band calibration• Observations in Bands 7–10 for the ACA or any 12-m array configuration may require band-to-band(B2B) calibration in order to find a suitably nearby and sufficiently bright phase calibrator to ensure
phase calibration quality. The ALMA OT will automatically check the availability of suitable phasecalibrators during proposal validation and will automatically trigger the B2B mode where required.
• B2B observations are subject to the availability of suitable calibrators as checked by the ALMA OT.
Some science targets, particularly at the highest frequencies (Band 10) and longest baselines (C-8 inCycle 10), may not be observable even with B2B where the constraints are most strict. The ALMA OT
will emit an error if a source does not have a suitable calibrator. PIs are advised to begin preparing
their High Frequency proposals early to ensure that a suitable calibrator is available for their targets. See
Section A.9.6; for technical details, see Section 10.5.5 of the Technical Handbook.

16• A maximum of 65 hours for the 12-m Array and 85 hours on the 7-m Array will be available for Band-toband calibration in Cycle 10.

4.3

Scheduling considerations

Apart from time-constrained observations, various aspects of a proposed observation such as weather conditions
or requested angular resolution and Largest Angular Structure (LAS) may affect when an observation is scheduled. This section describes the most important scheduling considerations that investigators should be awareof when preparing their ALMA proposal.
4.3.1

Weather

Chajnantor is one of the best sites in the world for ground-based observations at submillimeter wavelengths(Evans et al. 2003, ALMA Memo No. 471 and Maud et al. 2023, ALMA Memo No. 624; available from the
ALMA Memo Series). The opacity (primarily determined by the Precipitable Water Vapor – PWV) and thephase stability of the atmosphere are the two primary factors that dictate when ALMA can observe at certain
frequencies, in particular in the higher-frequency bands and at frequencies near atmospheric water absorption
lines. Both transmission and phase stability follow a yearly cycle (late southern winter is best – see Figures
2 and 4 of Memo 471) and a diurnal cycle (late night and early morning are best – see Figures 3 and 5 ofMemo 471); also see the “Preciptiable Water Vapour” and “Phase RMS” sections of Memo 624. In addition to
the transmission and phase stability criteria, the low wind speeds that typically occur during night and earlymorning provide optimum observing conditions.
Figure 2 shows the PWV measurements per month, illustrating the yearly cycle. The best months for highfrequency observations are from May to November. Figure 3 shows the percentage of time when the PWV isbelow the observing thresholds adopted for the various ALMA bands. The time percentage is shown per monthand separately for afternoon and night to highlight the daily and monthly variations. For a given time of the
day and a given month, the PWV measurements still show a large scatter due to the differences in weather
from year to year. During parts of the year, such as the Altiplanic winter4 season (December-March), it may bedifficult to carry out submillimeter observations. For this reason, an extended maintenance and upgrade period
is scheduled each February, during which no science observations are scheduled.
Figure 4 shows the percentage of time available when the Phase RMS variations are below 30 degrees as afunction of observing band and month of the year, for a fiducial 1000 meter baseline length, as measured over a
120 second timescale. The data come from the ESO-Allegro phase RMS study using over 15000 ALMA scienceobservations taken since Cycle 3 from which various phase RMS parameters and metadata were extracted(ALMA Memo No. 624). The measure of phase RMS over a given timescale can be used as a proxy for the
expected phase RMS that would remain in a target source after phase referencing calibration with a cycle time
similar to the timescale. A phase RMS of < 30 degrees can be considered as very-good to ideal conditions. For
baselines < 1000 meters there is a few percent reduction in time available with increasing timescales (up to∼ 240 seconds), while moving to longer baselines (∼ 10000 meters) reduces time by ∼ 10−15%, mostly at higher
bands, as compared to Figure 4. Note that ALMA uses cycle times of < 100 seconds for the longest baselines tocompensate for the intrinsically larger phase variability (see ALMA Memo No. 624 for further discussion). The
time available can be limited by either the PWV or by the Phase RMS, and which of these dominates depends
on the ALMA Configuration. For example, in longer-baseline observations (e.g., C-8) the phase RMS criteria
is a more severe restriction on the available time than the PWV criteria.
The JAO will schedule the observations during appropriate weather conditions to ensure good data quality. In
particular, high-frequency projects will be prioritized when weather conditions are appropriate for them.
4.3.2

Angular resolution

PIs can enter a single value or a range when specifying acceptable angular resolutions for a given SG in the
ALMA OT (see Section 4.5 for more on Science Goals). Whenever feasible, PIs are encouraged to enter a range
4 During southern summer, the high-pressure system over the Pacific Ocean weakens and moves southwards, allowing warm
humid air from the Amazons to flow over the Andes into northern Chile, causing rain and occasionally snow to fall on the usually
dry Altiplano: this phenomenon is known as Altiplanic winter.

176Band 1, Band 3

Precipitable Water Vapor [mm]

5

75%
50%
25%
10%

4

3

Band 4

2Band 5a, 61

Band 7, 8b
Band 8c
Band 5d, 9, 10

b400 GHz

er

De

ce

mb

er
mb

er
tob

ve
No

c492 GHz

Oc

pte

mb

er

st
Au

gu

ly

ne
Ju

y
Ma

ril
Ap

rch
Ma

ary
bru

Ju

Se

a203 GHz

Fe

Ja

nu

ary

0

d183 GHz

Figure 2: Fraction of time that the PWV falls below a given value along the year. The percentages shown
indicate the fraction of time that the PWV is under the PWV value indicated on the y-axis. For example, inMarch 75% of the PWV measurements are under 3.8 mm, and in June 75% of the PWV measurements fall
below 2.3 mm. The data were obtained with the APEX weather station, ALMA measurements, and weather
forecast data between January 2010 and January 2022. The horizontal dashed lines show the PWV observing
limits adopted for the ALMA bands for an elevation of 60 degrees.
spanning more than one configuration. Such a choice may improve chances of having the SB observed, especiallyfor SBs with an intrinsically low probability of execution (e.g., due to weather or time constraints).
In practice, the ALMA OT will assign to a given SB any number of configurations that fulfill the angularresolution range requested by the PI. For scheduling feasibility and Quality Assurance (QA) purposes, thefollowing will also be considered:• If the PI selects a single value for the angular resolution or a range narrower than 20% around its center
value, a range of ±20% around the single or center value specified will be enforced.
• If the requested range (after applying the previous rule) does not include the resolution of at least oneof the notional configurations, the range will be extended to include the resolution of the closest notional
configuration.
• If the requested range includes both long-baseline and more compact configurations, only the latter will beconsidered. An exception is constituted by ToO observations that can be triggered in any configuration if
the angular resolution requested by the PI is “any” (see Section 3.2).
The expected configurations and their associated beam sizes can be viewed via the “Planning and Time Estimate"" button in the ALMA OT “Control and Performance” panel. The final range of angular resolutions(i.e., after all the above factors have been considered) and the associated configurations will be displayed in the
Phase 2 SBs in the ALMA OT so that they can be reviewed by PIs. Users should note that the synthesized

18

60
40
20
0

night
afternoon
1 2 3 4 5 6 7 8 9 10 11 12

80
60
40
20
0

80

Band 7night
afternoon

60
40
20
0

1 2 3 4 5 6 7 8 9 10 11 12

Month

night
afternoon
1 2 3 4 5 6 7 8 9 10 11 12

100

100

Band 8 (492 GHz)night
afternoon

80
60
40
20
0

1 2 3 4 5 6 7 8 9 10 11 12

MonthBand 5 (203 GHz), Band 6

80
60
40
20
0

Month

Percentage of time when PWV < 0.66 mm

Percentage of time when PWV < 0.91 mm

Month

100

Band 4

Percentage of time when PWV < 1.80 mm

80

100

night
afternoon
1 2 3 4 5 6 7 8 9 10 11 12Month

Percentage of time when PWV < 0.47 mm

Band 1, Band 3

Percentage of time when PWV < 2.75 mm

Percentage of time when PWV < 5.19 mm

100

100

Band 5 (183 GHz), Band 9, Band 10
night
afternoon

80
60
40
20
0

1 2 3 4 5 6 7 8 9 10 11 12MonthFigure 3: The percentage of time when the PWV is below the observing thresholds adopted for the various
ALMA bands for afternoon (yellow; based on 17:00–21:00 UT) and night (green; based on 01:00–05:00 UT)
and for an elevation of 60 degrees. The horizontal line within the box indicates the median. Boundaries ofthe box indicate the 25th - and 75th -percentile, and the whiskers indicate the highest and lowest values of theresults. The data were obtained with the APEX weather station, ALMA measurements, and weather forecast
data between January 2010 and January 2022.
beam shape can be elongated, in particular for sources at high or very low declinations (see Section 7.4 of theTechnical Handbook for details). For reference, the ALMA OT will show the expected 2-D beam dimensions
and maximum axial ratio based on observations near transit for a given source. Observations away from transit
will result in a higher axial ratio than that shown.
PIs aiming to obtain a specific surface brightness sensitivity may enter their request in temperature units. In
this case, if a range of acceptable resolutions is specified by the PI, the time estimate will be determined by
the time needed to achieve the surface brightness sensitivity requested at the resolution of the most extended
configuration fitting the provided range (i.e., highest resolution). ALMA QA processes are defined in termsof resolution and flux density sensitivity, so the actual surface brightness sensitivity delivered will depend on
the resolution achieved by the observations (see Chapter 11 of the Technical Handbook). Thus, a temperaturesensitivity worse than requested could be obtained if the resolution achieved in the delivered images is still
within the requested range but higher than that of the most extended configuration assigned to that SB.
4.3.3

Configuration schedule for the 12-m Array

The ALMA 12-m Array will be configured in 8 different configurations during Cycle 10. While each configuration
contains fifty 12-m antennas, only a subset of the 50 antennas will be available for most observations due
to maintenance activities, calibration observations, and testing new capabilities. These operational factors

19Figure 4: The percentage of time when the phase RMS variability is . 30 degrees at the various bands for afiducial 1000 meter baseline, as measured over a 120 second timescale and with WVR correction applied. Notethe plot y-axis label indicates the phase RMS as a path length variation in microns. The range in atmospherictransmission across Band 5 does not affect the Phase RMS, so the frequency range is not separated as in
Figure 3. The available time for Band 8 is based on the Phase RMS measurements at high frequency end of theband (492 GHz) as a “worst case” scenario. “Day” denotes times between 07:00 and 19:00 local Chilean timeand “Night” is between 19:00 and 07:00 local Chilean time. The horizontal line within the box indicates themedian, while the boundaries of the box are the 25th and 75th percentiles. The data are from the ESO-Allegro
phase RMS study using over 15000 ALMA science observations taken since Cycle 3, from which phase RMS
parameters were extracted (see Maud et al. 2023, ALMA Memo No. 624).
impact the actual configuration achieved for a given observation, so the configurations used for simulations andplanning are referred to here as “notional configurations.” The ALMA OT assumes 43 antennas are available
when calculating the time estimates and image characteristics based on these configurations. Configurations
are now denoted as C-X, with X=1 for the most compact configuration and X=10 for the most extended (seeSection A.2 and Chapter 7 of the Technical Handbook for details)5 . The notional configurations C43-1 throughC43-10 used in Cycles 6 and 7 may be used to simulate observations using C-1 through C-10. Files describing
the notional configurations are available on the SP. The planned 12-m Array configuration schedule for Cycle 10
is given in Table 3. This schedule may be modified depending on the results of the proposal review process andthe proposal pressure in the different configurations. Changes to the configuration schedule will be announced
on the SP. On average, configurations change once every three weeks. Observations will not be scheduled in
February 2023 because of poor weather during the Altiplanic winter.
The first column of Table 3 gives the planned start date for each configuration. These dates are subject
5 These configurations are equivalent to the “C43-X” configurations that may be reported by other ALMA subsystems.

20

Start date

Configuration

Longest baseline

LST for best observing conditions

2023 October 1

C-8

8.5 km

∼ 22—10 h

2023 October 20

C-7

3.6 km∼ 23—11 h

2023 November 10

C-6

2.5 km

∼ 1—13 h2023 December 1

C-5

1.4 km

∼ 2—14 h2023 December 20

C-4

0.78 km∼ 4—15 h2024 January 10

C-3

0.50 km

∼ 5—17 h2024 February 1

No observations due to maintenance2024 March 1

C-1

0.16 km

∼ 8—21 h

2024 March 26

C-2

0.31 km

∼ 9—23 h2024 April 20

C-3

0.50 km∼ 11—0 h

2024 May 10

C-4

0.78 km∼ 12—2 h2024 May 31

C-5

1.4 km

∼ 13—4 h2024 June 23

C-6

2.5 km

∼ 15—6 h2024 July 28

C-5

1.4 km

∼ 17—7 h2024 August 18

C-4

0.78 km∼ 19—8 h2024 September 10

C-3

0.50 km∼ 20—9 h

Table 3: Planned 12-m Array Configuration Schedule for Cycle 10. Configuration properties are given in
Section A.2.
to change because of weather conditions. The second column gives the 12-m Array configuration, and thethird column lists the longest baseline for the configuration (see Table A-1 for corresponding resolutions andmaximum recoverable scales). The fourth column lists the LST ranges when the observing conditions are moststable, approximately two hours after sunset to four hours after sunrise (Section 4.3.1). The effective observing
time available per configuration for executing PI projects (excluding time spent on observatory calibration,
maintenance, reconfigurations, and other activities – see Section 4.3) is shown in Figure 5.
Given the anticipated configuration schedule and weather constraints, the following considerations apply:• Band 9 and 10 observations will be scheduled during the LST ranges given in the fourth column ofTable 3, corresponding to more stable weather conditions (Section 4.3.1). The amount of time with stable
atmospheric conditions suitable for Bands 7 and 8 observations outside of those LST ranges is limited (seeFigures 2 and 3). To maximize the completion of high-frequency observations, such projects are given
priority in the observing queue when the weather conditions are suitable (Section 4.3.1).
• High-frequency projects (Bands 7 to 10) and Band 5 observations near the atmospheric absorption feature
at 183 GHz are not recommended during the Altiplanic winter (December to March) at any LST.
• The probability of an observation being scheduled depends on the over-subscription for the given LST andconfiguration in addition to the required weather conditions.
• Projects that have imaging requirements (constraining the necessary configuration) and other time constraints (e.g., due to coordination with other observatories) that do not coincide cannot be scheduled.

21

Time available (hours)

40

Time available (hours)

40

Time available (hours)

40

Total
Large Programs
Band 8Band 9/10

30

C-1

C-2

40
30

30

20

20

10

10

10

0

0

0

20

C-4

C-5

40
30

30

20

20

20

10

10

10

0

0

0

30

30

20

20

10

10

0

0

4

8

12

16

LST (hours)

20

C-8

40

24

0

C-6

40

30

C-7

C-3

40

ACA

120
80
40

0

4

8

12

16

LST (hours)

20

24

0

0

4

8

12

16

LST (hours)

20

24

Figure 5: Estimated observing time available per configuration for executing PI projects, based on precipitablewater vapor (PWV) only. For example, approximately 30 hours are expected to be available in C-4 at LST
05 h for all observations and up to 15 hours of those may be allocated to Large Programs. The time available
for Large Programs is shown in pink and time for high-frequency observations in green and dark blue. The
configuration schedule and, consequently, the total number of hours available per configuration may change in
response to proposal pressure (Section 4.3.3). The data files containing these histograms are available here.
4.3.4

Observing pressure

Figure 6 shows the LST distribution of Cycle 9 submitted proposals and of those awarded grades A, B, or C
by configuration and array type. While some LST ranges such as 02–06 h or 12–19 h show over-subscription inseveral configurations, the degree of over-subscription differs significantly for different configurations. In general,
proposals will have a higher probability of acceptance if they request time in less subscribed LST ranges.
The range of angular resolutions provided by PIs (Section 4.3.2) will have a direct impact on the observingpressure per configuration. Proposals that specify a broad range of acceptable angular resolutions (i.e., several
acceptable configurations) increase their likelihood of being scheduled and executed. However, PIs should only
request the range of angular resolutions that is acceptable for their science goals, as this choice will be evaluatedduring the proposal review process.

4.4

Duplicate observations and resubmissions

4.4.1

Checking for duplications

Duplicate observations of the same location on the sky with similar observing parameters (frequency, angularresolution, coverage, and sensitivity) are not permitted unless scientifically justified. Detailed criteria of what

22

C-1

Time [hours]

400

C-2

C-3

C-4

C-5

C-6

C-7

C-8

C-9

C-10

Grades A/B/C
Requested

300
200
100
0

Time [hours]

400
300
200
100
0

Time [hours]

400

7-m

1000

Total Power

1000

300
200

500

500

100
0
0

5

10

15

LST [hours]

20

0

5

10

15

20

0
0

LST [hours]

5

10

15

LST [hours]

20

0
0

5

10

15

20

LST [hours]

Figure 6: Distribution of estimated execution time in Cycle 9 for all submitted proposals (gray) and proposals
assigned Grade A, B, or C (blue). The figure does not include the unfinished Cycle 8 2021 Grade A proposals
carried over to Cycle 9. Configurations C-9 and C-10 will not be visited in Cycle 10.
constitutes a duplicated observation are specified in Appendix A of the ALMA Users’ Policies.
PIs are responsible for checking their proposed observations against the Archive and the list of Grade A projects
in the observing queue provided on the Science Portal to avoid duplicate observations. PIs proposing duplicationsof previous cycle observations will not have their proposals marked as duplications if they had no way to know
about the previous cycle observations, using the resources listed above, by the release of the Call for Proposals.
Information on checking for duplications is available on the Duplicate Observations page on the Science Portal.
The proposal cover sheet contains a section where PIs can justify observations known to be duplicate. PIs may
wish to justify their proposed observations in cases where they are similar to previously executed or accepted
programs but are not formal duplicates. This will help the reviewers understand why new observations arerequested.
Examples of duplicate observations that may be approved include:• Observations of time-variable phenomena.
• A large-area survey where cutting out a smaller area to avoid overlap with a previous observation will
make the observation inefficient and increase the overall execution time.
• Spectral scan surveys where excluding a frequency range covered by a previous observation will make theobservation inefficient and increase the overall execution time.
4.4.2

Resubmission of an unfinished proposal

Proposal teams that submit a Cycle 10 proposal to observe some or all the SGs of an unfinished project will havethe relevant SGs identified as a “resubmission”. An SG is deemed a resubmission if it constitutes a duplicationof an existing SG following the rules specified in Appendix A of the ALMA Users’ Policies and the PI of therelevant project from any previous cycle is listed as a PI, Co-I or Co-PI of the corresponding Cycle 10 proposal

23

or the Cycle 10 PI is listed as an investigator on the relevant proposal from any previous cycle. For suchresubmissions, the relevant portion of the Cycle 10 proposal will be canceled if the observations are successfullycompleted in Cycle 9. Observations started in a previous cycle and accepted as a resubmission in Cycle 10 willcontinue to be observed with the setup of the previous cycle.
A Scientific Justification must be provided if the proposers request one or more additional epochs of observations
in Cycle 10 even if the Cycle 9 observations are completed.

4.5

Estimated observing time

Proposal requests are cast in terms of SGs, each containing a complete observational setup (desired sensitivity,
range of angular resolutions and LAS, frequency band, spectral windows, and spectral resolutions) to be applied
for one or more targets. The OT Quickstart Guide and the OT User Manual provide extensive details andguidance for preparing the SGs. Experienced users who wish to understand how ALMA observations are set up
may refer to Chapter 8 of the Technical Handbook.
The observational setup of a given SG is used to estimate a total observing time for that SG (except for solar
or VLBI observations or when overridden by the PI - see Appendix B). This observing time is the sum of therequired time on source for all science targets, time for all calibrations including overheads, and the time for any
additional array configurations needed to meet the specified LAS. The estimated observing time for the proposal
is the sum of the times for all SGs. The actual observing time to reach a given sensitivity, resolution, and LAS
will depend on the prevailing conditions when the project is observed, the number of antennas available, andthe actual array configuration.
The estimated time on source is calculated with the ALMA Sensitivity Calculator (ASC), available within the
ALMA OT or as a stand-alone web application on the Science Portal. The parameters that affect these time
estimates include requested sensitivity, source declination, observing frequency, spectral bandwidth, number ofantennas, angular resolution (if the sensitivity is specified in temperature units6 ), and default weather conditions.
A description of the ALMA Sensitivity Calculator is given in Chapter 9 of the Technical Handbook.
The estimated time for calibrations and overheads is calculated by the ALMA OT and will depend on thefrequency, configuration, and type of observation (e.g., full polarization observations require additional calibrations). Proposals requesting the suppression of some or all calibrations in one or more SGs may be deemed
technically infeasible if the request is not properly justified in the proposal (see Section B.4 for details).
For each SG, one or more SBs are generated during Phase 2 depending on the distribution of sources in thesky and the number of configurations needed (Sections A.8.1 and A.4, respectively). Each SB contains all thecommands needed to perform the observations and a complete set of calibrations. The minimum duration of
the SB is constrained by a minimum time on source of 5 minutes for the sum of all the sources in the SB or 50%of the total calibration time (see Section 5.3.5.3 of the OT User Manual). For SGs that require a combinationof arrays but have short time on source that is increased to the 5-minute minimum by the ALMA OT, thetime multipliers given in Table A-2 may not be preserved (see Section A.4). The maximum duration of a SB isaround 2 hours (determined by a maximum time on source of 50 minutes) and each SB will be re-run as manytimes as needed to achieve the requested signal-to-noise (S/N) ratio. Consecutive executions of a given SB (ifneeded) are favored during scheduling to maximize uv -coverage. However, if uv -coverage is fundamental for thescientific goals of a proposal, PIs should specify this request as a time constraint and, if necessary, override the
ALMA OT time estimate with the time needed to achieve such uv -coverage (see Section B.2 for details). Data
from each SB will be processed, assessed, and delivered independently.
The final factor in the time estimate is the possible addition of configurations needed to reach the LAS specified
by the user. The LAS is compared to the “Maximum Recoverable Scale” (MRS) of the configurations that best
match the requested range of angular resolutions. The MRS for each configuration is listed in Table A-1. If the
LAS exceeds the MRS of all matching configurations, then additional configurations, if allowed (Section A.4),
are added with a time estimated using the multipliers given in Table A-2. If the array combinations are notallowed (Section A.4), the ALMA OT will give a validation error. If the LAS can be achieved with one or more
6 Since Cycle 5, the time estimate adopts the configuration that fulfills the highest angular resolution requested if the sensitivity
is specified in temperature units (Section 4.3.3).

24

of the best-matching configurations, the remaining configurations meeting the angular resolution but not the
LAS request will not be considered.
The PI may include additional SGs for array combinations not allowed in a single SG, but each SG must be
separately justified and have its own performance specifications (sensitivity, range of angular resolutions, and
LAS).
Beginning this cycle, two types of correlator modes for the 12-m Array are offered in Dual Polarization: thetraditional 2x2 bit and a new 4x4 bit. The latter provides a significant increase in correlator efficiency, thattranslates to an increase of 12% in sensitivity (at fixed spectral resolution and integration time), or a corresponding reduction of the needed time to achieve a desired RMS by 25% (at a fixed spectral resolution). The
ALMA OT Time Estimates take into consideration whether the "Representative" spectral window is set to
2x2 or 4x4 bit mode. Data taken in these 4x4 modes can be combined with data taken with the ACA at thecorresponding spectral resolution mode. Because the ACA correlator does not have a 4x4 mode, the ACA SBs
will be generated with the equivalent 2x2 mode and corresponding time estimate.
Observations that require only the ACA are selected by checking a specific box in the ALMA OT interface.
When calculating the time required for the ACA, for each Science Goal the ALMA OT uses the TP Array time
if this array is required (based on LAS) or otherwise the 7-m Array time; i.e., it is not the sum of the 7-m and
TP Array time. In case of simultaneous observations in the 12-m and 7-m Arrays, the estimated time for the
7-m Array will be set equal to that of the 12-m Array.
Note that snapshots with the 7-m Array are strongly discouraged for imaging. For single pointings, integrationsof at least one hour are necessary for sufficient uv -coverage to achieve good image quality. Ensuring sufficient
uv -coverage for mosaics with the 7-m Array can be problematic because the integration time is spread out
over many pointings. For this case, simulations that assume the minimum number of guaranteed antennas arestrongly encouraged to help set the per-pointing integration time. See Chapter 7 of the Technical Handbook
for more information on imaging with ALMA.
Time estimates for each SG are available in the ALMA OT by clicking “Planning and Time Estimate” in the“Control and Performance” panel. A summary of the time estimate of each SG can be viewed by clicking the“Time Summary” button on the ALMA OT toolbar. The times for the 12-m Array, 7-m Array, and TP Array
are tabulated separately on the proposal cover sheet.

4.6

Supporting tools and documentation

4.6.1

The Observing Tool documentation

The ALMA OT, a Java-based application that resides and runs on the user’s computer, is used to prepare
and submit observing proposals (Phase 1) as well as to prepare the observations for execution on the telescope(Phase 2) if the proposal is accepted. The ALMA OT includes a number of tools and checks to ensure submitted
proposals conform to the Cycle 10 capabilities.
The ALMA OT is most conveniently installed using the new installer option, which is available for Linux, MacOS, and Windows. The installer contains its own version of Java and thus it is not necessary for users to installJava themselves.
The ALMA OT documentation suite, which provides all the basic information required to complete the proposal
preparation and submission, includes:• The OT Phase 1 Quickstart Guide: A guide to proposal preparation for the novice ALMA OT user. It
provides an overview of the necessary steps to create an ALMA observing proposal.
• The OT Video Tutorials: A visual demonstration of proposal preparation and submission with the ALMAOT. Users should note that these videos were produced in Cycle 6 and therefore do not include the changes
implemented since then.
• The OT User Manual: A manual intended for all ALMA users, from novices to experienced users. It provides comprehensive information on creating valid Phase 1 proposals and Phase 2 programs for observing
astronomical objects. It is also included as part of the “Help” documentation within the ALMA OT itself.

25• The OT Reference Manual: A manual providing a concise explanation for all the fields and menu itemsin the ALMA OT. It is also included as part of the “Help” documentation within the ALMA OT itself.
• The OT trouble-shooting page: A list of the ALMA OT installation requirements and workarounds forcommon installation problems.
• The known ALMA OT issues page: A list of known bugs, their status, and possible workarounds. This
page may be updated during the proposal submission period and should be checked first if problems areexperienced with the ALMA OT.
4.6.2

Additional proposal preparation tools

Two tools are available to help users produce simulated images of ALMA observations of simple or user-provided
science targets. The first simulation tool is integrated into CASA, the offline data reduction and analysis tool for
ALMA data. CASA includes the tasks “simobserve” and “simanalyze”, which generate simulated visibility data
and make images from these simulated data sets. An additional CASA task, “simalma”, simplifies the process
for ALMA data by combining data from multiple arrays, including the TP Array, if needed. These CASA tasks
require configuration files that specify the layout of ALMA antennas. To simulate observations for Cycle 10,
investigators can use the Cycle 10 configuration files available on the Science Portal. The CASA simulation
tasks are described in the CASA documentation and detailed examples can be found in the CASA guides.
Additional information on CASA, including hardware requirements and download instructions, is available at
the CASA website.
The second simulation tool is the ALMA Observation Support Tool (OST). The OST uses a simplified webinterface to help users generate ALMA simulations. Users submit jobs to the OST and are notified by email
when the simulations are completed. The OST documentation is available at the OST website.
A guide for simulating ALMA observations with either tool is available at the CASA guides website.
Splatalogue is a database containing frequencies of atomic and molecular transitions emitting in the radio
through submillimeter wavelength range. This database is used by the ALMA OT for spectral-line selection.
More information is available in the Splatalogue QuickStart Guide.
4.6.3

The ALMA Regional Center guides

The ARC Guides contain user support details specific to each ALMA regional partner. They are:
• The East-Asian ARC Guide• The European ARC Guide• The North American ARC Guide
4.6.4

Supplemental documentation

The documents described below supplement this Proposer’s Guide for the preparation of Cycle 10 proposals,
for either the novice or advanced users. All documents can be accessed via the ALMA Science Portal.
The Proposing Guidance page from the Science Portal summarizes the steps involved in the preparationand submission of an ALMA observing proposal. It is designed to help users find the relevant documents andsources of additional information in each step of creating a proposal.
Observing with ALMA: A Primer is a brief introduction to ALMA observing, submillimeter terminology,
and interferometric techniques that should prove useful for those new to radio astronomy. Several example
science projects are described.
The NAASC video series, the EU ARC network’s Interactive Training in Reduction and Analysis
of INterferometric data and the ALMA Explained series have video tutorials on a wide range of topics
related to interferometry and ALMA data analysis and archival queries.
The ALMA Users’ Policies document contains a complete description of the applicable users’ policies. The
long-term core policies for usage of ALMA and of ALMA data by the user community are presented.

26

The ALMA Cycle 10 Technical Handbook describes the technical details of ALMA during Cycle 10, including but not limited to receiver characteristics, array configurations, available observing modes, and correlator
setups, and the basis of the ALMA OT time estimates.
The ALMA Memo Series and ALMA Technical Notes Series include technical reports on various aspectsof ALMA project development and construction and from the extension and optimization of capabilities.

4.7

The ALMA Helpdesk

The ALMA Helpdesk can be accessed from the ALMA Science Portal or directly at http://help.almascience.org.
Submitted tickets are directed to the user’s ARC, where support staff are available to answer any question related
to ALMA, including but not limited to ALMA policies, capabilities, documentation, proposal preparation, the
ALMA OT, Splatalogue, and CASA. Users may also request information on workshops, tutorials, or about
visiting an ARC or ARC node for assistance with data reduction and analysis. Users must be registered at the
ALMA Science Portal to submit a Helpdesk ticket. Replies to an already existing ticket can be sent by the user
by logging into the SP or via email (see "Can I respond to my helpdesk ticket through my email?" for moredetails). ALMA staff aim to answer Helpdesk tickets within two working days.
The ALMA Helpdesk opens an Emergency Proposal Submission department 72 hours before the ALMA deadline.
It will appear in the department selection dropdown of the “Submit Helpdesk Ticket” page. The three ARCs
share responsibility for the tickets submitted to this department, to provide answers as quickly as possible. This
department is only to be used to address problems that block the submission of proposals; if the ticket does notmatch this condition, it will be moved out of the emergency department and answered by the staff from thecorresponding ARC.
ALMA staff will create a project ticket in the Helpdesk for each accepted proposal. Investigators can use thisticket for questions and communication on their project throughout its lifetime. Finally, investigators can also
trigger ToO observations using the Helpdesk (see Section 3.2).
The “Knowledgebase” of the Helpdesk is a database of answered questions and articles on all aspects of ALMA.
Users can search the Knowledgebase to find answers to common queries. Knowledgebase articles that match
their query are automatically suggested to users as they type. The Knowledgebase query interface also searches
all the documentation available on the ALMA Science Portal and provides a direct link to the documentationthat may answer a user’s question.

5

Proposal preparation, submission, and review

The following sections contain guidelines regarding proposal format and preparing the Scientific and Technical
Justification. The setup of Science Goals is only briefly explained here. Users are referred to the extensive suiteof ALMA OT documentation for details (Section 4.6.1). ALMA novices are encouraged to start with the OT
Quickstart Guide and the ALMA OT video tutorials.

5.1

Proposal format

An ALMA proposal consists of basic proposal information that is entered directly into the ALMA OT (Section 4.6.1). Proposal information includes a Science Justification uploaded to the ALMA OT as a PDF file,and one or more Science Goals (SGs). SGs contain the technical details of the proposed observations and must
include a Technical Justification.
After entering the basic proposal information and completing the SGs in the ALMA OT, the PI can generate
the PDF of the complete proposal, including the Scientific Justification, SGs, and Technical Justification thatwill be distributed to the reviewers for evaluation. The first page of the PDF (the “cover sheet”) includes thetitle and abstract together with a summary of the SGs. ALMA implements a dual-anonymous proposal review
so the names of investigators are not listed on the cover sheet or elsewhere in the PDF seen by the reviewers.

27

5.2

Dual-Anonymous proposal review

To ensure that the proposal review process is as fair and unbiased as possible, proposals at ALMA are reviewed
under a dual-anonymous system. In a dual-anonymous review, the proposal team does not know the identity of
the reviewers and the reviewers do not know the identity of the proposal team. While proposers will still enter
their names and affiliations in the ALMA OT, this information will not appear on the proposal cover sheet, or in
the tools used by the reviewers. It is the responsibility of the proposers to ensure anonymity is preserved whenwriting their proposals. Proposers are recommended to review the PDF file of their complete proposal (generatedusing the ALMA OT) to ensure that anonymity is preserved throughout the whole document. Proposals that do
not follow the dual-anonymous guidelines may be subject to disqualification. Details and specific guidelines on
how to write your proposal following the dual-anonymous requirements are provided in the Guidelines for DualAnonymous Proposals on the Science Portal. Proposers with resubmissions are encouraged to be particularly
cognizant of changes needed in their text. All proposers are encouraged to use the Helpdesk for any questions
relating to dual-anonymous review.

5.3

Preparing the Scientific Justification

ALMA Cycle 10 proposals must include a single PDF document that includes a science case written in English.
The document may include figures, tables, and references. The maximum permitted file size is 20 MB.
5.3.1

Page limits and fonts

The total length of the PDF document is limited to four pages for Regular, ToO, VLBI, Phased
Array, and DDT proposals and six pages for Large Programs (A4 or US Letter format), with a fontsize no smaller than 12 points. The ALMA OT will check the font size of the PDF and issue an error
during proposal validation if more than 15% of the text is smaller than 12 points. To submit the proposal,
any problems with small fonts must first be fixed. Note that the ALMA OT may issue errors by detecting“hidden text” when figures are cropped from other PDFs. See the Knowledgebase article on font size problems
for further details.
The recommended breakdown is two pages for the science case and two pages for figures, tables, and references,
but proposers are free to adjust these numbers within the overall page limit. The document for Large Programs,
which are allotted two additional pages, must include additional information as described below. Large Programs
are also required to submit a separate one-page PDF document with their management plan through the ALMAOT at the time of proposal submission (see Section 5.5 for more details).
Figures and tables may be embedded within the science case so that they appear close to the location where
they are referenced in the text. Although the Technical Justification for each Science Goal is entered in the
ALMA OT, any figure required for it needs to be placed in the Scientific Justification PDF document. Users areencouraged to prepare their Scientific Justifications using the LaTeX template available on the Science Portal.
Proposals must be self-contained. Reference can be made to published papers (including arXiv.org preprints)
as per standard practice in the scientific literature and they must be listed at the end of the science case.
Consultation of those references should not, however, be required for understanding the proposal.
5.3.2

Science case

Each proposal must describe the scientific importance of the proposed project and include a clear statement of
its immediate observing goals, including the suitability of the observations to achieve the scientific goals (seeSection 5.7.2 and guidelines for reviewers). It is also recommended to provide a brief justification of the requested
sensitivity and angular resolution, with full details provided in the Technical Justification (Section 5.4).
Proposers can simulate ALMA observations using different array components and configurations (see Section 4.6.2). Simulations are not required. However, if they are discussed in a proposal to justify any technicalaspects of an observation, their results (i.e., images and simulation details) should be included in the Scientific
Justification and referenced in the relevant Technical Justification.
Proposal reviewers are selected with expertise that covers the various topics within a proposal category. There-

28

fore, the Scientific Justification should be written for a knowledgeable but broad-based audience.
Large Programs In addition to the information described above, the Scientific Justification for Large Programs should include the following information:• An assessment of the scheduling feasibility. Large Programs should be designed to be completed
within one Cycle given the configuration schedule and weather constraints, and the program must satisfy
the configuration/LST restrictions applicable to Large Programs as described in Section 3.3.
• A description of the data products (including any non-ALMA products) that will be delivered by the team for ingestion into the ALMA archive. This should include the timeline fordelivery and a discussion of how the delivered products will benefit the community.
• A publication plan. This should indicate the major publications anticipated for this project and thetimeline for publication.
5.3.3

Figures, tables, and references

Figures, tables, and references that support the science case and the Technical Justification may be included.
Figure captions, tables and references must use a font size no smaller than 12-points and, together
with the science case, must fit within the overall page length and 20 MB size limit of the PDF proposal.

5.4

Preparing the Technical Justification

Each SG within a proposal must contain a Technical Justification (TJ), which is entered directly into the ALMAOT in the TJ node of each SG. Any figures associated with the TJ must be included in the Scientific Justification
PDF file and clearly referenced in the TJ. The TJ must include a quantitative description and justification of the
expected source brightness, the requested sensitivity and S/N ratio, angular resolution, maximum recoverable
scale, and spectral setup. An incomplete TJ may lead to the rejection of the proposal on technical grounds.
The TJ must abide by the guidelines of dual-anonymous review.
Each SG has its own TJ because the technical setup of the observations will often vary substantially from one
SG to the next. If a TJ is applicable to more than one SG, the TJ node can be easily copied and pasted (ordragged and dropped) between SGs. The TJ node contains three sections – sensitivity, imaging, and correlator
configuration – corresponding to the main aspects that need to be assessed for the technical feasibility of any
proposal. Each section includes at least one free-format text box that must be filled in (50 characters minimum),as well as a number of parameters computed from the user input captured in that Science Goal. This information
is designed to help with the writing of the TJ, and will also highlight potentially problematic setups (in bluetext) if applicable. Please see the relevant sections in the OT Reference Manual (accessible by clicking the “?”symbols within the ALMA OT) for details. If the ALMA OT detects any technical choices that require an extra
justification (e.g., time-constraints), appropriately labeled text boxes will appear in an additional "Choices tobe justified" section.
Given that the information and the text boxes displayed in the TJ node are dependent on information provided
elsewhere in the SG (including the Expected Source Properties entered in the Field Setup node), the Science Goal
should be completed before filling in the TJ. Specific guidelines on filling out the TJ are given in Appendix B.
If a proposal does not conform to the advertised capabilities, it can be declared technically infeasible either
during the proposal review process or during Phase 2 (Section 6.1). The final decision will be made by the Headof Science Operations at the JAO.

5.5

Management Plan for Large Programs

In addition to their Scientific and Technical Justifications, all Large Programs must include a one-page management plan. The management plan should demonstrate that the proposal team has the personnel and computing
resources available to complete the project successfully in a timely fashion. This document does not need to beanonymized, and it should include:• A description of the overall organization of the proposing team.

29• The name and affiliations of, at minimum, the major participants of the proposing team and their responsibilities within the proposed project.
• An estimate of the data size for the data products and a demonstration that the proposing team has accessto sufficient computing resources and storage to process the data. The ALMA OT reports estimated data
rates and overall data volumes that can be used as a guide to estimate the volume of raw data thatwould be delivered. It is not uncommon for the final data volume to double after full calibration and thegeneration of imaging products.
The ARCs can provide assistance to Large Program teams in optimizing the observing strategy for their proposals and preparing the management plans. PIs are encouraged to contact their ARCs early in the proposal
process to receive assistance on any of these needs and to ensure the availability of the necessary computing
and storage resources.

5.6

Proposal validation, submission and withdrawal

After the proposal is validated within the ALMA OT, it can be submitted to the ALMA Archive. Validation
could take up to 5 minutes (or longer!) if the program contains complicated setups or a large number (hundreds)of sources. PIs of such programs should submit their proposals well before the deadline. A proposal can be
updated and submitted again to the ALMA Archive as many times as needed by the PI before the proposal
deadline. Each time a proposal is submitted, the previous version of the proposal is overwritten (Section 5.6.1).
Submitted proposals cannot be modified after the deadline. DDT proposals are not overwritten when submitted
again, so they should only be submitted once.
Proposals will be accepted starting at 15:00 UT on 12 April 2023 and until the proposal deadline at 15:00
UT on 10 May 2023. No proposal submissions or updates will be accepted after the deadline. It is the
PI’s responsibility to submit the proposal successfully before the deadline. PIs are encouraged to submit their
proposals early.
In addition, the following considerations apply:• PIs, Co-Is and Co-PIs can retrieve proposals from the Archive both before and after the deadline.
• PIs who successfully submit their proposal will receive a confirmation e-mail from ALMA that includes
the assigned project code.
• DDT proposals may be submitted at any time. Like all other proposals, they must include a detailed
science case and Technical Justification.
• A Helpdesk ticket should be submitted if the PI needs to withdraw a proposal that has already been
assigned a project code.
5.6.1

Proposal updates

PIs who need to update and then resubmit a proposal should ensure that this is done using the last submitted
version either by (i) modifying the proposal saved after submitting it (i.e., saved from the ALMA OT as a .aotfile), or (ii) downloading and then modifying the submitted proposal from the Archive using the ALMA OT.
If a PI tries to submit a version of the proposal that had been saved on disk before it was first submitted, it
will be rejected by the Archive. An earlier version that was never submitted (and which therefore contains no
proposal code) will produce a new (duplicate) submission with a new code.
Users wishing to generate a new proposal starting from a proposal from the current submission period shouldsave the original one to disk before it has been submitted. Otherwise, the second proposal will contain theoriginal proposal’s code and will overwrite it when submitted. Alternatively, the ALMA OT’s "Open Projectas New Proposal" (available from the File menu) could be used. Users wishing to generate a new proposal
from a project file corresponding to a proposal submitted in a previous cycle should use “Open Project as New
Proposal” to open the project as an unsubmitted proposal for the current cycle.

30

5.7

Proposal evaluation and selection

5.7.1

Peer review

ALMA will continue the use of a distributed peer review process for scientific review of most proposals submitted
to Cycle 10. Proposals requesting less than 50 hours on the 12-m Array and all ACA stand-alone proposals
requesting less than 150 hours on the 7-m Array will be evaluated in this way. The review process is summarized
below; for additional details, including guidelines for the reviewers and the expected timeline, see the Proposal
Review section of the Science Portal.
Except for Large Programs, the PI of each proposal must designate themselves or a Co-I as a reviewer at thetime of submission. In most cases the PI will be the designated reviewer. Nonetheless, to keep the workload
to a manageable level, it is recommended that reviewers review at most three Proposal Sets. The maximum
allowed number of Proposals Sets to be reviewed by a single reviewer is five. This maximum number is not yet
enforced by the ALMA OT, but will be checked by the Proposal Handling Team (PHT) at the JAO after the
proposal deadline. If a reviewer has been selected to receive more than five Proposal Sets, the reviewer will becontacted by the PHT to designate another reviewer among the proposal Co-Is. If the reviewer does not identify
alternative reviewers by 15 May 2023, the PHT will reject the reviewer’s proposal(s) with the highest proposalcode(s) until the maximum allowed number of Proposal Sets to review is reached. Thus, PIs are encouraged todesignate one of their Co-Is as reviewer on one or more proposals when submitting multiple proposals. Moreinformation is provided in the Distributed Peer Review page on the Science Portal.
After the proposal deadline, the PHT will assign ten proposals to the designated reviewer of each proposal.
The proposal assignment will be done based on the expertise of the designated reviewer as specified in theiruser profile7 . The assignment process will also consider possible conflicts of interest. If the designated reviewer
provides a list of their conflicts of interest in their user profile, the assignment process will take this information
into account and the reviewer will not be assigned proposals for review in which the PI, a Co-PI, or a Co-I
are in their list. If no list of conflicts is provided, the assignment process will identify conflicts based on thedesignated reviewer’s past ALMA collaborations. During the review process, if the reviewer identifies a conflictof interest in their assigned proposals, they can request a replacement proposal through the Reviewer Tool.
Then during Stage 1, the reviewer will rank the ten proposals (1-10, strongest to weakest) in order of scientificpriority and write a review for each proposal. If ranks and reviews are not submitted by the Stage 1
review deadline at 15:00 UT on 28 June 2023, the proposal on which the reviewer is acting as
the designated reviewer will be declined.
After the Stage 1 review deadline, each reviewer will have the option to participate in Stage 2 of the review
process, where the anonymized comments from the other reviewers of the same proposals will be made available.
During Stage 2, reviewers can modify their own ranks and comments if desired. After this second stage iscompleted, the ranks from all reviewers of each submitted proposal will be combined to produce a global ranked
list of proposals.
Any PI and most Co-Is can be designated as a reviewer. If the PI does not have a Ph.D. at the time of proposal
submission (e.g., a student), the PI can still be the reviewer, but a mentor (who must have a Ph.D.) must be
identified at the time of the proposal submission. A PI may designate a Co-I as the reviewer as long as the
Co-I has a Ph.D. in astronomy or a closely related field. When planning to submit multiple proposals, PIs areencouraged to designate a Co-I as reviewer. The reviewer and (if needed) mentor must be designated in the
ALMA OT at the time of proposal submission.
Large Programs will be reviewed by a single panel, the ALMA Proposal Review Committee (APRC). The APRC
will be composed of 16-18 members of the scientific community drawn from the five ALMA science categories.
Barring conflicts of interest, all members of the APRC will review all submitted Large Programs. Proposers
should take special care to write their proposals for a broad audience considering the different expertise of
the members of the APRC. For each Large Program, the PHT will select one member of the APRC to act as
7 We encourage all ALMA users to go to the ALMA Science Portal to update their user profile and select keywords pertaining
to their expertise. The distributed review proposal assignment algorithm will use the selected keywords of the reviewer’s expertisefor matching assignments; if reviewers do not submit them, the algorithm will use the keywords of the submitted proposal. Review
assignment matching is therefore optimized for individual reviewers’ expertise when the information provided in the users’ profile
is up to date and accurate.

31

the Primary Assessor; they will be in charge of leading the discussion and write the consensus report. This
assignment is done based on the expertise of the APRC members and the science category selected by the PI
when submitting their proposal (see Appendix D for the list of scientific categories). To gain further expertise,
Large Programs will also be reviewed by external Science Assessors, who will provide written reports for the
APRC to consider during the meeting. The APRC will take all reviews into consideration and will recommend
which Large Program to schedule.
After the outcome of the proposal review process is approved by the ALMA Director’s Council and a Chilean
representative, the results will be communicated to the PIs. The notifications will include the assigned grade
and a consensus report from the APRC that summarizes the strengths and weaknesses of the proposal.
5.7.2

Evaluation criteria

The primary criteria to rank all proposals are the overall scientific merit of the proposed investigations andtheir potential contribution to the advancement of scientific knowledge. The guidelines for the reviewers containdetailed review criteria. The proposals will also be evaluated for technical feasibility to ensure they are consistent
with Observatory best practices.
Given the significant investment of ALMA resources for Large Programs, the APRC will also consider thefollowing factors for these programs:• Scheduling feasibility
A Large Program should be designed such that the observations are likely to be completed within
Cycle 10 given the antenna configuration schedule and weather constraints (see Sections 3.3 and
4.3). The scheduling feasibility of each Large Program will be evaluated and communicated to
the APRC.
• Value-added data products and publication plan
A Large Program should describe the value-added data products that will be produced to achieve
its science goals and their value to the community, as well as present a plan to publish the resultsof the project. The program teams will be expected to deliver these data products to ALMA sothat they can be made available to the community at large.
• Management plan
The APRC will evaluate the management plans to assess if the proposal team is prepared tocomplete the project in a timely fashion, both in terms of personnel and computing resources.
The management plans will be evaluated only after the APRC has completed the scientificrankings of the Large Programs. The evaluation of the management plan will not be used tomodify the scientific rankings. Any concerns that the APRC has about the management of a
Large Program will be communicated to the ALMA Director, who will make the final decisionon whether to accept the proposal.
5.7.3

Proposal selection

The results from the APRC and the distributed peer review will be used to form an observing queue based
primarily on the scientific rankings from the review process.8 The formation of the observing queue will also
take into account the scheduling constraints dictated by the configuration schedule and weather, the share ofobserving time for each region, and the time constraints on Large Programs and VLBI.
Up to 33% of the nominal time specified in Section 4.1 will be assigned to Grade A proposals and 67% to Grade
B proposals. Grade C will be assigned to proposals for filler time to ensure that an adequate number of projects
are available for all configurations and LST ranges in case the actual observing efficiency or weather conditions
differ from expectations.
The shares of the observing time among the regions are:
8 For VLBI proposals, both ALMA and the appropriate VLBI network must accept a given proposal for the observations to bescheduled.

32

• 33.75% for the European Organisation for Astronomical Research in the Southern Hemisphere (ESO).
• 33.75% for the National Science Foundation of the United States (NSF).
• 22.5% for the National Institutes of Natural Sciences of Japan (NINS).
• 10% for the Chilean community, which is administered jointly by the Agencia Nacional de Investigacióny Desarrollo (ANID) and the Universidad de Chile.
All regions contribute toward “Open Skies” to enable all eligible Principal Investigators (Section 2.5) to apply
for ALMA time.

5.8

Proposal confidentiality

For proposals assigned Grade A or B, the project code, the proposal title and abstract, the name and regionof the PI, and the names of Co-Is (and Co-PIs, in the case of Large Programs) will be made public soon afterPIs are informed of the outcome of the proposal review process. This information is provided on the “Highest
Priority Projects” page of the Science Portal. For proposals assigned Grade C, the corresponding information
will be made public as soon as its first data are archived.
Proposal metadata (for example the source positions, observation frequencies, and integration times) for Grade
A will become public soon after the proposal review process is completed. For Grade B and C proposals,
metadata will be made public as soon as the first data are archived. The metadata for proposals with Grade U
or unobserved Grade B or C proposals will remain confidential.
The Scientific and Technical Justifications of all submitted proposals remain confidential, except for proposals
for 0.87 mm and 1.3 mm VLBI proposals, which will be sent for technical review by the Event Horizon Telescope Consortium (EHTC) VLBI network, and joint proposals, which will be sent to the appropriate partner
observatories for technical evaluation.

6

Post-proposal activities

6.1

Observation preparation and submission: Phase 2

Once a project has been approved for scheduling, the project passes into Phase 2. PIs will not be required
to submit Phase 2 Science Goals in Cycle 10 (see ALMA Users’ Policies for further details). Each approved
project will be assigned an ALMA Contact Scientist (CS) at the associated ARC or ARC node and a project
Helpdesk ticket will be opened on behalf of the PI for communication with the CS and others. Necessary minorchanges may be requested through this Helpdesk ticket and can usually be implemented as long as they do not
impact the science scope or increase the total execution time. Any significant change may only be made after
the approval of a PI-initiated change request through the Helpdesk (Section 6.2). The CS can assist the PI withany questions during Phase 2.
ALMA staff will generate the Scheduling Blocks (SBs) and, in case of problems, will contact the CS and thePI. An SB is defined as the minimum set of instructions describing an ALMA observation that can be fully
calibrated (see Chapter 8 of the Technical Handbook for more details regarding hierarchical level of an ALMA
observing project). If no problems are found, the project will be submitted to the ALMA observing queue toawait execution at the telescope. PIs may track the status of their SBs through the Snooping Project Interface(SnooPI), accessible from the ALMA Science Portal.
For approved solar observations, the ALMA staff will coordinate with the PI to get an updated target ephemerisat least 24 hours in advance of the proposed observation. PIs of observations with ephemeris targets other thanthe Sun are responsible for providing a valid target ephemeris file during the Phase 2 process and any updates
during the Cycle if necessary.

33

6.2

Changes to submitted programs

Changes to a submitted proposal will not be permitted prior to the completion of the review process. Therefore,
PIs should carefully check source coordinates, frequency and angular resolution settings, and calibration needs
before submitting their proposal. PIs are encouraged to use the Helpdesk if they need support.
PIs of proposals assigned a grade of A, B, or C may request changes to their projects subject to the ALMA
Change Request policies described in the ALMA Users’ Policies. Minor changes can usually be made, but PIs arestrongly encouraged to make any necessary requests well in advance of the potential scheduling of observations.
Major changes are allowed only if additional information that may seriously affect the scientific case of the
project has become available since the time of submission, when there is a demonstrable mistake, or when thereis the potential for interesting scientific optimization.
All change requests are made through the ALMA Helpdesk. The request must include a clear description of the
proposed change along with a clear, substantive justification for the change. Major change requests are treatedcase-by-case and evaluated taking into account the increase in science scope, change of observing time, changes
in the observing setups, and other factors. Change requests leading to duplications against ALMA proposals in
the observing queue or archival observations will not be approved.

6.3

Data processing and data delivery

ALMA staff, assisted by the ALMA Data Reduction Pipeline, will conduct quality assurance on ALMA data
and will provide processed data products through the respective ARC archives. Quality Assurance Level 2(QA2) is performed on the data that result from all executions of an SB. In particular, the data are checked
for calibration accuracy and to assure there are no imaging artifacts (see ALMA QA2 Data Products for moredetails). Data that meet the PI-specified goals within cycle-specific tolerances (see Chapter 11 of the TechnicalHandbook) are made available to the PI. Once the products have been identified as suitable for delivery, the PI
is notified that the data are available for download through the ALMA Archive. PIs are requested to check thedelivered data as soon as practical. If the PI discovers a problem in the delivered data other than any caused
by a PI mistake, they must submit a Quality Assurance Level 3 (QA3) request to the Helpdesk as soon as
possible, since such problems will have implications for re-observations and the proprietary period. For a moredetailed description of the Quality Assurance process, see the ALMA ALMA Users’ Policies and Chapter 11 of
the Technical Handbook.
By default, data obtained as part of an ALMA science program are subject to a proprietary period of 12 months(except DDT programs, which have a proprietary period of 6 months), starting for each data package when the
PI is notified that the data are available (see the ALMA Users’ Policies).
At any time, a PI can use the science portal to request access to raw data for any execution that has passed
Quality Assurance Level 0 (QA0). This request modifies the start of the proprietary period: once the raw data
are staged for PI access, the proprietary time starts for that SB. See the ALMA Users’ Policies for more details
on requesting raw data or contact the ARC for support.

6.4

Opportunities for public promotion of ALMA

If a PI believes their results are newsworthy or of interest to a broader community, the PI should contact the
ALMA Education and Public Outreach (EPO) team to develop materials for presentation to the media andthe public (e.g., press releases), including support in the preparation of visuals, if relevant. EPO may ask forcooperation on the scientific content and for the PI to be available for possible interviews. The e-mail address
for the ALMA EPO team is alma-iepot@alma.cl.

34

A

ALMA Cycle 10 Capabilities

This appendix describes the characteristics and capabilities of ALMA offered for Cycle 10. All submitted
proposals must be compliant with these capabilities or they will be judged as infeasible. Where possible, the
ALMA OT has validation checks to warn the user or to prevent the user from entering unallowed values.

A.1

Number of antennas

At least forty-three 12-m antennas in the main array (hereafter the 12-m Array) will be offered. The ACA will
have available at least ten 7-m antennas (hereafter the 7-m Array) for short baselines and three 12-m antennas(hereafter the Total Power Array or TP Array) for making single-dish maps. The ACA will be offered bothto complement observations with the 12-m Array and as a stand-alone capability. The stand-alone ACA isoffered either with the 7-m Array alone or with the 7-m Array and TP Array combined. The ALMA OT
currently does not permit users to request only the TP Array (see Section A.3 if TP Array observations areneeded to supplement archival 7-m Array data). Proposals requesting stand-alone ACA time are subject tocertain restrictions, including no bandwidth switching, no solar observations, no user-specified calibration, andno Astrometric observations. The use of the TP Array is limited to spectral-line observations (not continuum)in Bands 3 to 8.
The number of antennas available may sometimes be fewer than the numbers given above due to unforeseen
problems with the equipment, or during array reconfigurations. During these times, ALMA staff aim to scheduleobservations that will not be seriously affected by having a slightly smaller number of antennas and may increase
the integration times to compensate for the reduced sensitivity or reduced instantaneous uv -coverage, wheneverpractical.

A.2

Array configurations

As detailed in Section 4.5, a Science Goal is defined in terms of a desired range of angular resolutions (ARs) andthe Largest Angular Structure (LAS) to be imaged. ALMA will meet these requirements by taking observations
in one or more array configurations, which are characterized in terms of their AR and Maximum Recoverable
Scale (MRS, the largest smooth angular structure to which a given array is sensitive – see Chapter 7 of theTechnical Handbook for details). The properties of these configurations, and the allowed combinations, therefore
define the imaging capabilities of ALMA.
The antennas in the 12-m Array will be staged into configurations that transition from the most compact(with maximum baselines of ∼160 m) up to the most extended configuration (maximum baselines of 8.5 km in
Cycle 10). Eight 12-m Array configurations have been defined to represent the possible distribution of antennas
over this range of maximum baselines. These are denoted as C-X, with X=1 for the most compact configuration
and X=10 for the most extended. These configurations are equivalent to the “C43-X” configurations that may bereported by other ALMA subsystems. One 7-m Array configuration has been defined to represent the possible
distribution of the ten 7-m antennas. The imaging capabilities of these configurations are given in Table A-1.

A.3

Total Power Array

The TP Array is used to recover extended emission when mapping angular scales up to the size of the requested
map areas. TP Array observations are included only if the LAS cannot be achieved with the 7-m Array, andthe TP Array can only be used for spectral-line observations (not continuum) in Bands 3 to 8. No Band 9 orBand 10 TP Array observations are offered for this cycle. Thus, angular scales greater than the 7-m Array MRS
listed in Table A-1 cannot be recovered for any observations in Bands 9 and 10, or for continuum observationsin any band.
The TP Array cannot be requested in a stand-alone mode using the ALMA OT. However, if a user has existing
7-m Array data through their own program or through archival data, but now realizes that TP Array data areneeded to obtain short spacings, they can submit a proposal requesting both the 7-m Array and TP Array. The
proposal should indicate that only the TP Array is needed and that the 7-m Array should be descoped if the
proposal is accepted. This option is available only if the 7-m Array data have already been obtained.

35

Config.

Band

1

3

4

5

6

7

8

9

10

Freq. (GHz)

40

100

150

185

230

345

460

650

870

45 m

θres (arcsec)

31.5

12.5

8.35

6.77

5.45

3.63

2.72

1.93

1.44

9m

θM RS (arcsec)

167

66.7

44.5

36.1

29.0

19.3

14.5

10.3

7.67

161 m

θres (arcsec)

8.45

3.38

2.25

1.83

1.47

0.98

0.74

0.52

0.39

15 m

θM RS (arcsec)

71.2

28.5

19.0

15.4

12.4

8.25

6.19

4.38

3.27

314 m

θres (arcsec)

5.75

2.30

1.53

1.24

1.00

0.67

0.50

0.35

0.26

15 m

θM RS (arcsec)

56.5

22.6

15.0

12.2

9.81

6.54

4.90

3.47

2.59

500 m

θres (arcsec)

3.55

1.42

0.94

0.77

0.62

0.41

0.31

0.22

0.16

15 m

θM RS (arcsec)

40.5

16.2

10.8

8.73

7.02

4.68

3.51

2.48

1.86

784 m

θres (arcsec)

2.30

0.92

0.61

0.50

0.40

0.27

0.20

0.14

0.11

15 m

θM RS (arcsec)

28.0

11.2

7.50

6.08

4.89

3.26

2.44

1.73

1.29

1.4 kmθres (arcsec)

1.38

0.55

0.36

0.30

0.24

0.16

0.12

0.084

0.063

15 m

θM RS (arcsec)

16.8

6.70

4.47

3.62

2.91

1.94

1.46

1.03

0.77

2.5 kmθres (arcsec)

0.78

0.31

0.20

0.17

0.13

0.089

0.067

0.047

0.035

15 m

θM RS (arcsec)

10.3

4.11

2.74

2.22

1.78

1.19

0.89

0.63

0.47

3.6 kmθres (arcsec)

0.21

0.14

0.11

0.092

0.061

0.046

0.033

0.024

64 m

θM RS (arcsec)

2.58

1.72

1.40

1.12

0.75

0.56

0.40

0.30

8.5 kmθres (arcsec)

0.096

0.064

0.052

0.042

0.028

0.021

0.015

0.011

110 m

θM RS (arcsec)

1.42

0.95

0.77

0.62

0.41

0.31

0.22

0.16

Lmax
Lmin

7-m

C-1

C-2

C-3

C-4

C-5

C-6

C-7

C-8

Table A-1: Angular Resolution (θres ) and maximum recoverable scale (θM RS ) values for different 7-m Arrayand 12-m Array configurations are shown for one representative frequency in each ALMA receiver band. The
value of θM RS is computed using the 5th percentile baseline (L05) from Table 7.2 and Equation 7.6 of theTechnical Handbook. The value of θres is the mean size of the interferometric beam obtained through simulations
with CASA. Computations were done for a source at zenith; for sources transiting at lower elevations, the NorthSouth angular measures will increase proportional to 1/sin(elevation). Lmax and Lmin are the maximum andminimum baseline lengths in the array, respectively. All angular measures scale inversely with observed sky
frequency. Calculations are based on the notional C43-X and 7-m configurations. Band 1 will not be available inconfigurations C-7 and C-8. C-9 and C-10 are not offered in Cycle 10; θres and θM RS for these two configurations
are provided in the Technical Handbook.

A.4

Allowed array combinations and time multipliers

Only certain array combinations are allowed to meet the specifications of a given Science Goal (SG). A SG canuse no more than two 12-m Array configurations, and 7-m Array observations are only allowed in conjunction
with 12-m Array observations if one of the three most compact 12-m Array configurations is required. TP Arrayobservations are allowed only if 7-m Array observations are also obtained (and subject to the restrictions in thepreceding section). The allowed combinations are given in Table A-2 (with empty cells indicating combinations
that are not allowed), and are built into the ALMA OT validation.

36

For the resulting data to be combined based on the sensitivity and weighting between the allowed 12-m, 7-m
and TP Array configurations, the different arrays must be observed in the correct proportion, depending on thenumber of overlapping baselines (see Chapter 7 of the Technical Handbook for details). These are expressed interms of multiplicative factors with respect to the time required in the most extended configuration (which inturn is set by the user-requested sensitivity and angular resolution). The adopted time multipliers are given in
Table A-2, and are reported in the ALMA OT.
Most Extended
configuration

Allowed Compact
configuration
pairings

7-m Array

TP

C-1

7-m Array & TP

C-2

Extended
12-m Array
MultiplierMultiplier
if compact
12-m ArrayneededMultiplier if
7-m ArrayneededMultiplierif TP Arrayneeded andallowed

1

1.7

1

7.0

11.9

7-m Array & TP

1

4.7

7.9

C-3

7-m Array & TP

1

2.4

4.1

C-4

C-1 & 7-m Array
& TP

1

0.34

2.4

4.0

C-5

C-2 & 7-m Array
& TP

1

0.26

1.2

2.1

C-6

C-3 & 7-m Array
& TP

1

0.25

0.6

1.0

C-7

C-4

1

0.23

C-8

C-5

1

0.22

Table A-2: Allowed Array Combinations and Time Multipliers. See Chapter 7 of the Technical Handbook forrelevant equations and detailed considerations. If the array configuration that meets the AR request according
to Table A-1 has a MRS that is smaller than the LAS request, the OT checks if adding more compact array
configurations, following the restrictions of this Table, fulfills the LAS request. If so, the final setup consists ofthe selected combination of arrays. Otherwise, the OT returns a validation error. C-9 and C-10 are not offered
in Cycle 10; please see Section 7.8 of the Technical Handbook for details on array combinations involving thoseconfigurations.
If more than one configuration is needed to satisfy the AR and LAS constraints of a given SG, separate
Scheduling Blocks (SBs) will be prepared during Phase 2 (Section 6.1) for each required configuration. These
will be observed independently, and the data from the different SBs will be calibrated and imaged separately.
An exception to the rules above occurs when requesting simultaneous observations with the 7-m Array and the
12-m Array. In this case the 12-m Array configuration is limited to C-1 through C-6 and only a single 12-m
Array configuration will be observed (e.g., if observations are taken in C-6, C-3 will not be observed). The TP
Array also be included if required to satisfy the LAS constraints. See the Technical Handbook for more details.

A.5

Receivers

Bands 3 to 10 are available on all antennas and Band 1 is expected to become available on 12-m Array antennas
starting in March 2024. For Cycle 10, observations with Bands 3 through 10 are offered in 12-m Array configurations up through C-8 (see Section A.2). Band 3 to 10 are offered on the 7-m Array. Observations with Bands
3 through 8 are offered on the TP Array (see below).
There are three types of receivers: dual-sideband (2SB), where the upper and lower sidebands are separated37

in the receiver and then processed separately, double-sideband (DSB), where the sidebands are super-imposedcoming out of the receiver but are separated in later processing, and single-sideband (SSB). All bands receive
dual linear polarizations (X and Y).
Table A-3 summarizes the properties of the receiver bands offered in Cycle 10. Details can be found in Chapter
4 of the Technical Handbook.
Band

Frequency range

Wavelength range

IF range

Type

(GHz)

(mm)

(GHz)

1

35 – 50

8.5 – 64 – 12SSB

3

84 – 116

3.6 – 2.6

4–8

2SB

4

125 – 163

2.4 – 1.8

4–8

2SB

5

158 – 211

1.9 – 1.4

4–8

2SB

6

211 – 275

1.4 – 1.1

4.5 – 102SB

7275 – 373

1.1 – 0.8

4–8

2SB

8

385 – 500

0.78 – 0.60

4–8

2SB

9

602 – 720

0.50 – 0.42

4 – 12DSB

10

787 – 950

0.38 – 0.32

4 – 12DSB

Table A-3: Properties of ALMA Cycle 10 Receiver Bands. These are the nominal frequency ranges forcontinuum observations. Observations of spectral lines that are within about 0.2 GHz of a band edge are notpossible (at present) in Frequency Division Mode (FDM, see Section A.6.1) because of the responses of thespectral edge filters implemented in the correlator. IF is the intermediate frequency.
The capability to switch rapidly between receiver bands within the same SG (except for the purposes of datacalibration) is not offered.
Water Vapor Radiometer (WVR) measurements to correct for fluctuations in atmospheric water vapor areavailable for all 12-m antennas. No WVRs are installed in the ACA 7-m antennas and no WVR corrections will
be applied to 7-m Array observations.
A.5.1

Considerations for Band 1

Proposals will be accepted for spectral line and continuum observations, including mosaic and spectral scanobservations, in Band 1 only with the 12-m Array. Full polarization observations will not be provided. Observations of the accepted Band 1 projects are anticipated to start in March 2024. Consequently, PIs should selectangular resolutions achievable with configurations available from that date (likely C-1 through C-6). Please also
see Section 8 of the Technical Handbook for technical considerations in Band 1.
A.5.2

Considerations for Bands 9 and 10

For observations in Bands 9 and 10, PIs should take the following considerations into account. Because thesidebands can be separated reliably only in interferometric observations, single-dish Bands 9 and 10 observations
with the TP Array will not be offered in Cycle 10. At Bands 9 and 10, a special correlator mode (90-degree
Walsh Switching) is available. For every spectral window defined by the user, enabling this feature will produce
another spectral window in the other sideband, mirrored around the√value of Local Oscillator 1 (LO1). Thismode doubles the continuum bandwidth to 15 GHz, thus producing a 2 improvement in sensitivity or reducing
the time required to achieve a particular sensitivity by a factor of 2. In addition, the greater bandwidth coverage
allows more spectral lines to be observed simultaneously, although aligning the spectral windows such that they38

cover additional transitions is difficult and thus this mode is currently restricted to the widest-bandwidth spectral
windows. In Cycle 10, 90-degree Walsh Switching will be activated by default for continuum and spectral-line
setups, although for the latter it will be possible (but not recommended) to deactivate it.
Owing to the complexity of the atmospheric absorption in Bands 9 and 10, calibration will be more problematic(this also applies to Band 8 and the high-frequency end of Band 7). Band 9 and 10 ACA 7-m Array observations
will be more difficult to calibrate than the corresponding 12-m Array observations because the rapid atmosphericphase correction cannot be applied and the smaller collecting area will limit the network of usable calibrators.
In particular, bright calibrators are sparse at these high frequencies. When possible, the JAO will include 12-m
dishes from the TP Array in the 7-m Array observation to support calibration; no special action or request isrequired by the PI. All these factors (in addition to the limited uv -coverage) will affect imaging at Bands 9 and
10 and will limit the achievable dynamic range with the ACA 7-m Array. Imaging dynamic ranges up to 50 are
typical for these bands (see Section A.9.1 for more details).
No mosaics are offered for Band 10 observations.

A.6

Spectral capabilities

A.6.1

Spectral windows, bandwidths and resolutions

The ALMA Intermediate Frequency (IF) system provides up to four basebands (per parallel polarization) thatcan be independently placed within the two receiver sidebands. For 2SB receivers (Bands 3 to 8 – see Table A3), the number of basebands that can be placed within a sideband is 0, 1, 2, 3, or 4. The placement of thebasebands is restricted for these receivers in that it is not possible to place three basebands in one sideband
and the fourth baseband in the other (see Chapter 6 of the Technical Handbook for details). This restriction
does not apply for DSB receivers (Bands 9 and 10).
The 12-m Array uses the 64-input Correlator, the 7-m Array uses the ACA Correlator, and the TP Array uses
the ACA Spectrometer. These correlators offer the same spectral setups. The 64-input Correlator operates in
two main modes: Time Division Mode (TDM) and Frequency Division Mode (FDM). TDM provides modest
spectral resolution and produces a relatively small data set. It is used for continuum observations or forspectral-line observations that do not require high spectral resolution. FDM provides high spectral resolution
and produces much larger data sets. A total of six correlator setups with different bandwidths and spectral
resolutions are available in the traditional 2x2 bit mode. Five new 4x4 modes are also offered this cycle (seeTable A-4).
For each baseband, the correlator resources can be divided across a set of “spectral windows” (spw) that canbe used simultaneously and positioned independently. Up to four spectral windows per baseband are allowedin the 2x2 bit modes (both for the 64-input Correlator and the ACA Correlator). In addition, starting in
Cycle 10, the 64-input Correlator can have one 4x4 bit spectral window per baseband (4x4 bit modes cannot
be used in the same baseband with 2x2 bit modes, but a mixture of basebands using 4x4 and basebands using
2x2 is allowed). The correlator can be set to provide between 120 and 3840 channels within each spw (for 4x4
bit modes, the number of channels is fixed to 1024), and the fraction of correlator resources assigned to each
spw sets the number of channels and the bandwidth available within it. The sum of the fractional correlator
resources spread across all spectral windows must be less than or equal to one (120 or 3840 channels in total).
The default correlator setup for FDM modes applies a spectral averaging factor of 2 (for 4x4 bit modes, thisis not needed because of the reduced number of channels). This has the advantage of halving the data rate
to produce more manageable data cubes, while reducing the spectral resolution by only 15%. However, an
additional consideration when selecting the spectral averaging is that data taken over different time periods(e.g., different configurations or multiple observations within the same configuration) are not guaranteed to beprecisely aligned in frequency. Therefore, the spectra will need to be interpolated onto a common frequency gridin CASA. If the expected linewidth is poorly sampled at the resolution of the spectrometer, it is recommended
that no channel averaging be applied (i.e., a spectral averaging value of 1) to improve the accuracy of theinterpolation (see Chapter 5 of the Technical Handbook for more information). Each correlator has a maximum
data rate (70 MB/s for the 64-input Correlator) and the ALMA OT will issue a validation error if a given SG
exceeds that data rate. For any spectral setup requiring an average data rate of more than 40 MB/s, PIs will

39Bandwidth

ChannelSpectral

Number of

Correlator

Bitspacing

resolution

channels

mode

Mode

(MHz)

(MHz)

(MHz)

1875

15.6

31.2

120

TDM

938

0.976

1.952

1024

FDM

4x4 ?

1875

0.488

0.976

3840

FDM

2x2

469

0.488

0.976

1024

FDM

4x4

938

0.244

0.488

3840

FDM

2x2

234

0.244

0.488

1024

FDM

4x4

469

0.122

0.244

3840

FDM

2x2

117

0.122

0.244

1024

FDM

4x4

234

0.061

0.122

3840

FDM

2x2

58.6

0.061

0.122

1024

FDM

4x4

117

0.0305

0.061

3840

FDM

2x2

58.6

0.01530.0305

3840

FDM

2x2

Table A-4: Properties of ALMA Cycle 10 Correlator Modes, dual-polarization operation. These values arefor each spectral window and for each polarization, using the full correlator resources and no on-line spectral
binning. The 4x4 bit modes are only available for the 64-input Correlator, and they provide higher correlator
efficiency for a given spectral resolution and integration time compared with the 2x2 bit modes. The bandwidthof the 4x4 bit modes is 1/4 of that of the 2x2 bit mode with the same spectral resolution. Single-polarization
modes are also available for the 2x2 bit modes, giving twice the number of channels per spectral window, andhalf the channel spacing of the above table. The “Channel spacing” is the frequency separation between data
points in the output spectrum. The spectral resolution – i.e., the FWHM of the spectral response function –is larger by a factor that depends on the “window function” applied to the data to control the ringing in the
spectrum. For the default function – the “Hanning” window – this factor is 2 See Chapter 5 of the TechnicalHandbook for details. These values apply only to the 64-input Correlator. (?) This 4x4 bit mode cannot berequested if the data has to be combined with ACA 7-m observations.
be contacted during Phase 2 to discuss the possibility of reducing the data rate.
Different correlator modes can be specified for each baseband, but all spws within a given baseband must use thesame correlator mode. For example, a high-resolution FDM mode can be used for spectral-line observations in
one baseband (with up to four independently placed FDM spectral windows), while the other three basebands
can be used for continuum observations using the low-resolution TDM mode. And while each spw within abaseband must use the same correlator mode, they can each be assigned a different fraction of the correlator
resources and each use a different spectral averaging factor, providing a broad range of simultaneously observed
spectral resolutions and bandwidths. Spectral windows can overlap in frequency, although the total continuum
bandwidth for calculating the sensitivity is set by the total non-overlapped bandwidth.
The 4x4 modes offered in Cycle 10 are only available for the 64-input Correlator. For spectral-line projects that
include 4x4 spectral windows and require ACA observations, the set-up that will be used on the ACA Correlator
will be the 2x2 mode listed in the Table with the same spectral resolution (and four times the bandwidth). This
bandwidth will guarantee that no sensitivity is lost on ACA calibration observations that benefit from wider

40

spectral coverage. Please note that one of the 4x4 modes (i.e., 938 MHz bandwidth) cannot be combined withACA Correlator observations, and that it can only offered for the 12-m Array.
Users are encouraged to enter the redshift or velocity of the target in the ALMA OT when feasible, as opposed
to calculating the sky frequency themselves. Entering the expected redshift or velocity will allow automatedline searches and identifications in the Archive or with external tools.
A.6.2

Science Goals with more than one tuning

An SG can include up to five tunings per group of sources within 10 degrees on the sky, except for SGs thatrequest long-baseline configurations, for which the grouping is limited to sources within 1 degree. Spectral scansor observations of targets with different radial velocities can thus be achieved within the same SB.
Each SB is self-contained for calibration. Therefore, multi-tuning SGs result in bandpass, amplitude, and gain
calibrators being observed for each tuning in the SB. For SBs that can be completed in a single execution, thisscheme is quite efficient. However, for SBs that require multiple executions, the available time for science targets
in each execution is reduced, and the resulting SBs can be quite inefficient. For such observations, separatingeach tuning into its own SG can lead to more efficient SBs and lower overall time estimates.
Spectral scan mode
A special case of the multiple tuning SG is the Spectral Scan mode, which is useful for spectral surveys or
redshift searches. It is possible to set up a spectral scan observation to include all three arrays (12-m, 7-m, TP)
or ACA stand-alone, depending on the required angular resolution range. The ALMA OT will automaticallyconfigure a set of contiguous spectral windows to cover a specified frequency range. The following restrictions
apply:• Angular resolution and LAS are computed for the Representative Frequency of each SG.
• No more than five frequency tunings per target are used, all in the same band.
• Only one pointing per target is used (no mosaics or offsets are allowed).
• Full polarization cannot be selected.
• TP spectral scans are only permitted for Bands 1 and 3–8.

A.7

Polarization

In addition to the dual-polarization (XX, YY) and single-polarization (XX) modes, observations to measure
the full intrinsic polarization (XX, XY, YX and YY) of sources are also offered for 12-m Array TDM and FDM
observations in Bands 3 to 7 as well as the stand-alone 7-m Array in Bands 3 to 7. For the 7-m Array, only linear
polarization is guaranteed to meet the ALMA specification, and only within one third of the primary beam.
While PIs will receive data that will allow them to generate circular polarization data, scientific commissioning
has not been done and the quality and/or accuracy of that data at this time is not assured.
When a Dual Polarization setup is used, separate spectra are obtained for the cross-correlated parallel hands(XX and YY). These will give two independent estimates of the source spectrum that can be combined to
improve sensitivity.
In Single Polarization mode, only a single input√ polarization (XX) is recorded. For a given resolution, thisresults in reduced sensitivity (by a factor of 2) compared with the Dual Polarization case, but one can use
either a factor of two more bandwidth for the same spectral resolution (unless the maximum bandwidth was
already being used) or a factor of two better spectral resolution for the same bandwidth.
For single-pointing polarization observations, targets must have a user-specified largest angular structure lessthan 1/3 of the primary beam for linear polarization, and less than 1/10 of the beam for circular. The expected
minimum detectable degree of linear polarization, defined as three times the systematic calibration uncertainty,
is 0.1% of the peak Stokes I (i.e., total unpolarized) flux for on-axis sources for both TDM and FDM observations
within 1/3 of the primary beam. This limit does not depend on the source size (i.e., compact or extended). The
minimum detectable degree of circular polarization is 1.8% of the peak Stokes I flux for both TDM and FDM

41

observations within 1/10 of the primary beam. Note that the systematic calibration uncertainty can degrade bya factor of ∼ 2 depending on the quality of the polarization calibrator and observation conditions (see Chapter 8of the Technical Handbook for more details). The frequency settings for single-pointing continuum polarization
measurements can be specified by the user, but the ALMA OT supplies default setups as detailed in Table A-5.
For FDM mode, polarization observations at any frequency setting within Bands 3, 4, 5, 6 and 7 are allowed,
but the spectral setup has to be the same for the polarization calibrator and the science target.
Band

spw1

spw2

LO1

spw3

spw4

Maximum Velocity Resolution

(GHz)

(GHz)

(GHz)

(GHz)

(GHz)

(km/s)

3

90.5

92.5

97.5

102.5

104.5

5.603

4

138.0

140.0

145.0

150.0

152.0

3.852

5

196.0

198.0

203.0

208.0

210.0

2.788

6

224.0

226.0

233.0

240.0

242.0

2.420

7

336.5

338.5

343.5

348.5

350.5

1.671

Table A-5: Default frequencies for Continuum Polarization Observations. Fixed central frequencies for four
TDM spectral windows, each of width 1.875 GHz, and the corresponding LO1 setting. Frequencies were chosen
to optimize spectral performance, and they are centered in known low noise and low instrumental polarization
tunings of the receivers. The last column shows the maximum allowed spectral resolution for mosaics in fullpolarization, corresponding to a spectral resolution of 1.953 MHz in each Band. This table assumes that eachbaseband is populated with a single spectral window (spw) centered on the baseband frequency.
Mosaics are supported for linear polarization continuum maps using the 12-m Array but not yet for the standalone 7-m Array. The spectral setup for polarization mosaics is limited to the current default continuum
frequency setups. Therefore, the PI will not be able to choose the frequency tuning of a given spectral window
freely for a polarization mosaic. The PI can, however, choose between the TDM and FDM modes, but with arestricted frequency resolution when the FDM mode is chosen. This scheme has been implemented to allow for
better continuum identification when mapping some sources of interest. The maximum spectral resolution thatcan be selected for FDM polarization mosaicking is 1.953 MHz, and the corresponding velocities for each Bandare shown in Table A-5.
For linear polarization mosaics, the 150-point restriction per SG remains in place. The mosaic pattern canbe arbitrary, but ALMA recommends a hexagonal grid when possible. While Nyquist sampling (half a beam
overlap) is sufficient, a sampling sparser than Nyquist (i.e., a more “loosely packed” mosaic) must be justified.
A proposal requesting a mosaic sampling rate sparser than Nyquist may be rejected on technical grounds. The
average error estimates for linear polarization mosaics are 1 degree in polarization position angle, and 0.1% inpolarization fraction in the regions of the mosaic that correspond to the inner 1/3 FWHM of a given pointing.
Near the FWHM of a given pointing, the estimated upper limits are 4 degrees and 0.5% (see Chapter 8 of theTechnical Handbook for details).

A.8

Source restrictions

Source positions are designated by: 1) fixed RA and DEC; 2) RA and DEC at epoch 2000.0 with a linear propermotion; or 3) an ephemeris that gives the RA and DEC as a function of time. All positions should be in ICRS
(J2000). Source names that are composed of only numbers (e.g., “7462356”) are not allowed and the ALMA OT
will issue a validation error if such a source name is entered.
At low elevations, it is possible for foreground array elements to block or “shadow” the signal received bybackground antennas, compromising the sensitivity and imaging characteristics of an observation (see Section
7.3 of the Technical Handbook for details). Therefore, observations of extremely high and low declination
targets should be avoided, particularly in compact configurations. For the 12-m Array, this shadowing becomes42

significant (> 5%) in the most compact configuration for sources with declinations lower than −65◦ or higher
than +20◦ . For the ACA, shadowing becomes significant for sources with declinations lower than −70◦ orhigher than +25◦ . The adopted upper declination limit for ALMA is +47◦ , corresponding to a maximum
elevation of 20◦ at the ALMA site. The ALMA OT gives a warning for objects from +37 through +47◦
declination, corresponding to transits between 20- and 30-degrees elevation. The ALMA Sensitivity Calculator
takes shadowing into account when determining time estimates.
A.8.1

Source Science Goal restrictions

A single SG is constrained to include one set of observational parameters that apply to all sources includedin that goal. This includes angular resolution (either a single value or a range), sensitivity, LAS, and receiverband. There is no restriction on the number of SGs per proposal.
For sources distributed widely in the sky the SG will be split by the ALMA OT into different “clusters”, eachgrouping all sources within 10 degrees (1 degree for SGs requiring long-baseline configurations). For eachgrouping within the SG, the total number of pointings must be less than or equal to 150. Pointings with the
ACA, if used in concert with 12-m Array observations, do not count against this 150-pointing limit.
The sources in a SG are further subjected to the following restrictions:• All the sources in a SG must be defined by the same field setup – either all as rectangular fields, or all as
individual positions.
• Sources must use the same spectral setup (relative placement and properties of spectral windows).
• For a given group of sources clustered within 10 degrees on the sky (or 1 degree for long-baseline configurations), there cannot be more than 5 separate tunings.
A.8.2

Rectangular fieldA rectangular field (also referred to as a mosaic) is specified by a field center, the length, width and orientationof the field, and a single spacing between the pointing centers. Observations are conducted using the “mosaic”
observing mode. This mode repeatedly cycles through all the pointings in the mosaic so that the imaging
characteristics across the map are similar.
The ALMA OT will set up a uniform mosaic pattern based on a user-specified pointing separation, and willcalculate the time to reach the required sensitivity considering any overlap. Non-Nyquist spatial samplings areallowed but must be justified in the Technical Justification.
If ACA observations are requested as part of a mosaic, then a corresponding 7-m Array mosaic will also be
observed. If these include TP observations, the mosaic area(s) will be covered by the TP Array using on-the-fly
mapping.
An SG may include multiple sources, each of which can have a differently sized rectangular field. The collectionof mosaics is subject to the source SG restrictions given above.
A.8.3

Individual pointings

PIs may choose to define a “custom mosaic” by specifying a set of individual, overlapping, pointing positions.
Gaps in pointings are not allowed. Custom mosaics are subject to all the source SG restrictions given above.
The interferometric data will be combined in post-processing to produce a single image. If ACA observations
are requested as part of a 12-m Array SG, then the corresponding 7-m Array observations will be obtained usinga Nyquist-sampled mosaic pattern that covers the 12-m Array pointings. If these include TP observations, themosaic area(s) will be covered by the TP Array using on-the-fly mapping.
Pointings that do not overlap within a given SG must be included as different field sources within the SG.

43

A.9

Calibration

The ALMA Observatory has adopted a set of strategies to achieve good calibration of the data (see Chapter
10 of the Technical Handbook). Requests for changes in these strategies will only be granted in exceptional
circumstances and must be fully justified. The default option is automatic calibrator selection by the system
at observing time, but some flexibility exists in choosing the actual calibrator sources in the ALMA OT. Userselected calibrators must be justified as they may result in decreased observing efficiency and/or calibration
accuracy.
A.9.1

Imaging dynamic range

The standard ALMA data reduction with nominal phase stability should be sufficient to produce images withdynamic ranges (peak continuum flux to map rms) up to ∼ 100 for the ACA and for compact 12-m Arrayconfigurations. For configurations more extended than 2 km and at frequency Bands 8, 9, and 10, the imaging
dynamic range may be closer to 50.
Images of bright sources may be dynamic-range-limited rather than sensitivity-limited. Their image quality
may be improved with self-calibration. For more information please see the Knowledgebase article “What ismeant by imaging dynamic range?” and Section 10.5.1 of the Technical Handbook.
A.9.2

Absolute flux accuracy

Absolute amplitude calibration will be based on observations of objects of known flux density, including eight
Solar System objects and a set of 40 quasars whose flux densities are monitored every 15 days. It is expectedthat these calibrators provide an absolute flux accuracy better than 5% for Bands 1, 3, 4 and 5; 10% for Bands
6, 7 and 8; and 20% for Bands 9 and 10. The decrease in accuracy at the higher frequencies is caused by variable
atmospheric opacity, pointing errors, and coherence loss due to uncorrectable short term phase fluctuations in
the flux calibrator.
A.9.3

Bandpass accuracy

The amplitude and phase shape of the spectral response for each antenna in the array is measured by observing
a bright source, usually a quasar, for the time needed to reach the desired spectral sensitivity for the relevant
spectral resolution. The accuracy of this shape particularly affects projects that intend to observe spectralfeatures that cover a significant fraction of a spectral window, and/or study faint spectral features in thepresence of strong continuum. A spectral dynamic range (i.e., the desired signal-to-noise ratio per spectral
resolution element) of 1000 has been demonstrated for Bands 3, 4, and 6, and a spectral dynamic range of 400,
250, 170, and 150 has been demonstrated for Bands 7, 8, 9, and 10, respectively. For Band 5, a limit similar
to Band 6 may be assumed, except for setups near the 183 GHz atmospheric absorption line. We expect aspectral dynamic range of 1000 in Band 1. The achieved spectral dynamic range will depend on the brightnessof the bandpass calibrator, the observing frequency, and spectral resolution (see Section 10.4.6 of the TechnicalHandbook for details). Proposals that request higher accuracy need to provide a feasible calibration strategy
in the Technical Justification or the proposal may be rejected on technical grounds.
A.9.4

Total Power calibration

The intensity calibration for single-dish observations with the TP Array is made by using the Amplitude
Calibration Device (ACD), which results in an intensity scale in terms of the corrected Rayleigh-Jeans antenna
temperature TA * (K). To combine the TP data with the interferometric data, the intensity scale is converted
from K to Jy. The conversion factor is a function of the observed frequency, half-power beam width, andaperture efficiency of the TP Array antennas. The latter two are derived from regular single-dish calibration
observations. The overall accuracy for the total power calibration is about 5% at Bands 3 to 7, increasing to
15% at Band 8.

44

A.9.5

Astrometry

The absolute positional registration of an ALMA image on the sky depends on the angular resolution and thequality of the phase calibration. With a stable atmosphere, a calibrator-target separation of less than aboutfour degrees, and a signal-to-noise ratio of the target image >20, the nominal accuracy of the absolute position
measurement (standard deviation) is at best ∼ 5% of the synthesized beam for angular resolutions larger thanabout 150 mas. At higher angular resolutions, the best absolute astrometric accuracy decreases to ∼ 10% of thesynthesized beam. If the astrometric goals are within these ranges, then the observing schedule, observations,and data reduction will be similar to a standard imaging proposal. This option appears explicitly in the ALMAOT as a button labeled “Standard positional accuracy (default)” (see Section “a” below) in the “Astrometry”
panel in the Calibration Setup editor.
The “Enhanced positional accuracy” option (Section “b” below), meanwhile, applies to astrometric projects inwhich the main scientific goals include measuring the celestial position of the science target to better than
the nominal expectation, or measuring the position change of a target over a period of hours to years in a
multi-epoch experiment.
To reach the desired astrometric accuracy, the optimum choices of the observing frequency, configuration, andtime on target will depend on the properties of the target (spectrum, angular size, brightness) and should
be chosen by the PI (see Section "a" below). Proposers of astrometric-type projects with the science goal ofmeasuring a source’s position are also encouraged to seek help via the Helpdesk.
In the ALMA OT, the editor panel referring to the positional accuracy can be found in the Calibration Setup editor. The default “Standard positional accuracy (default)” option provides the same default calibration strategy
as in previous cycles.
a) Standard positional accuracy (default): The choice of observing frequencies and configurations will depend on
the science goal and source properties (see more details in the Technical Handbook, Chapter 10). Many previous
astrometric programs requiring high precision have used Band 6 or 7 with configurations similar to C-4 to C-7,
since these combinations commonly provide good phase stability and are less constrained by weather conditions
than higher frequencies and longer baselines. Note that increasing the S/N of the image peak intensity above
20 will not improve the absolute astrometric accuracy. For lower values (<20), consider the equation in the
Astrometry section of Chapter 10 of the Technical Handbook, but a minimum S/N of 15 is recommended.
b) Enhanced positional accuracy: An astrometric proposal should select the “enhanced” option in the Calibration
Setup if (1) significantly better than nominal astrometric accuracy is needed, or (2) multi-epoch observations
over weeks or months are requested (i.e., using different 12-m Array configurations). In these cases, the PI
should contact ALMA staff through the Helpdesk. The reason for selecting the “enhanced” option must be
justified in the Technical Justification (see Section B.4).
For Cycle 10, the PI should contact ALMA staff via the Helpdesk concerning the possible choices of phasecalibrators and the choices of configurations and observation dates for longer-term multi-epoch observations.
Experienced PIs may use the “User-defined calibration” option to request the use of multiple or specific calibrators. Nevertheless, while doing so, the PI is requested to select the “Enhanced positional accuracy” and, again,
to double check the strategy with ALMA staff via the Helpdesk. The proposed strategy must be described in
the Technical Justification.
A.9.6

Phase calibrator search in Bands 7 to 10 at the longest baselines

To ensure accurate phase calibration and successful imaging in Bands 7 to 10 the phase calibrator must be
located suitably close to the science target and must be observed frequently enough to correct for the variable
atmospheric phase fluctuations. To achieve the former, the phase calibrator must be within the separation
angles listed in Table A-6. In order to achieve the latter, the phase calibrator is typically visited more regularly
than for lower frequency observations (see Section 10.5.5 of the Technical Handbook for details).
In the cases for any observations at Bands 7 to 10, the ALMA OT checks whether a suitable phase calibrator
exists within the specified separations on the sky from the science target as given in Table A-6, by searching
the online ALMA Calibrator Source Catalogue. This happens automatically during proposal validation and

45

ACA

C-1 & C-2

C-3 & C-4

C-5 & C-6

C-7

C-8

Band 715 degrees

12 degrees

11 degrees

10 degrees

7 degrees

6 degreesBand 815 degrees

9 degrees

9 degrees

8 degrees

7 degrees

5 degreesBand 910 degrees

9 degrees

8 degrees

7 degrees

6 degrees

4 degreesBand 108 degrees

8 degrees

7 degrees

6 degrees

5 degrees

3 degrees

Table A-6: Maximum separation angle between phase calibrator and science target. Note that C-9 and C-10
are not available for Cycle 10.
submission. The default spectral setup for the phase calibrator is the same as for the target source initially. If
the ALMA OT cannot find a suitable phase calibrator within the allowable separation on the sky or if the total
bandwidth of the spectral setup is narrower than 937.5 MHz, the ALMA OT then automatically switches tosearch for a phase calibrator by widening the aggregate bandwidth of the phase calibrator (bandwidth switchingmode BWSW). If the ALMA OT still cannot find a suitable phase calibrator, the ALMA OT automaticallyswitches the phase calibrator’s spectral setup to a lower frequency band (B2B mode – see details below) to
search for a stronger phase calibrator. No input is required from the PI when this occurs. Proposals withtargets that do not have a suitable phase calibrator found by the ALMA OT will trigger a validation error andsuch proposals cannot be submitted, this is most likely for Band 10 configuration C-8.
B2B phase calibration
B2B mode uses a phase calibrator observed at a lower frequency as compared with the science target frequency.
Because phase calibrators are brighter at lower frequencies, B2B calibration increases the chances that a suitablephase calibrator can be found close enough to a science target for accurate phase transfer. In addition to thephase calibrator being observed at a lower frequency, there is an added short bandpass observation at the
low-frequency and an additional strong calibrator - the Differential Gain Calibration (DGC) source – which isobserved at both frequencies to facilitate the calibration of the gain offsets between the high (science) and low(reference) frequencies. The band pairings are listed in Table 10.1 of the Technical Handbook. Note that there
are two types of B2B mode, the harmonic and non-harmonic types, which allow the full coverage of Bands 7
to 10 when B2B is triggered. The former type allows frequency switching within ∼ 3 s, while the latter takes∼20 s and has a lower overall efficiency. The type of B2B used depends primarily on the frequency of the sciencetarget tuning and is selected automatically by the ALMA OT. Further details can be found in Section 10.5.3 of
the Technical Handbook.

A.10

Time-constrained observations

Monitoring observations and time-constrained projects are offered subject to the following restrictions:• Observations to be performed with two 12-m Array configurations to satisfy the PI requests of AR and
LAS within a SG are not allowed to have time constraints.
• Observations with one 12-m Array configuration and the ACA are allowed to have time constraints only
if simultaneous observations with the two arrays have been requested.
• No restrictions will be imposed on the size of the time window specified by PIs for time-critical observations.
The scheduling feasibility of any proposal will depend on the total number of constraints that are imposed
and on whether the time window takes place during other activities on the array such as engineering orcomputing time. Whether such observations are technically feasible will be decided on a case-by-casebasis. In particular, observations with strict timing constraints but many possible time windows may befeasible.
• Programs that require more than two hours of continuous observations to monitor a source cannot be
guaranteed due to variable weather conditions and system interruptions. Proposers may request monitor-

46

ing observations longer than two hours, but if the observations fail after two hours, the observations will
not be repeated. Monitoring observations will be interrupted by regular calibrations. Investigators should
contact their ARC through the Helpdesk for support on such observations.
Stand-alone ACA proposals requesting only observations on the 7-m Array are allowed to have time constraints.

A.11

Solar observations

Proposals will be accepted for ALMA interferometric and Total Power observations of the Sun with the following
capabilities and restrictions:• Solar observations will be conducted only during the periods when the 12-m Array is in one of the allowed
configurations for the requested band, namely C-1 to C-4 for Band 3, C-1 to C-3 for Band 5, C-1 to C-3
for Band 6, and C-1 to C-2 for Band 7 (see configuration schedule in Table 3).
• The interferometric component of solar observations will be conducted using a special combined arraycomprising both 12-m and 7-m antennas (to ensure sufficient short-spacing information is observed), except
for solar polarization observations, which will only be observed using the 12-m Array. Observations will beprocessed with the 64-input Correlator (Section 5.1 of the Technical Handbook). Observations with only
the 7-m Array are not offered. Observations using only the 12-m Array will only be offered for Band 3
polarization observations.
• Observations will be carried out between 10:00 and 17:00 CLT (13:00 UT and 20:00 UT) when antenna
elevations are above 40 degrees, to minimize shadowing of 7-m antennas. This limitation will also be
applied to solar polarization observations.
• PIs may designate a desired range of angular resolutions. However, the available range is restricted to therange provided by the 12-m configurations allowed for Bands 3, 5, 6, and 7, as described above.
• The Total Power component of solar observations consists of fast-scanning mapping observations to recover
the largest angular scales for interferometric observations. Proposals requesting only Total Power singledish observations will not be accepted. The Total Power observations will be taken contemporaneouslywith the interferometric observation. These observations will not be executed when the Sun is at elevations
above 70 degrees because the required fast-scan azimuth slew speeds are too high.
• There are two options for the field of view of the Total Power solar observations. One is covering a fullsun. Its shape and size of the field of view is a circle with 2400 arcseconds diameter. The time cadence offull-sun images is about 10, 13, 15, and 25 minutes for Bands 3, 5, 6, and 7, respectively. The other option
is a small field of view around a region of interest, called “Fast Regional Mapping” (FRM). The shape ofa field of view is a circle, the same as the full-sun scan, but the diameter of the circle can be changed
by PI. The center coordinate of the field of view is fixed by the ephemeris used for the interferometricobservation. When a science goal has multiple fields, FRM cannot be chosen for the science goal. The
time cadence of solar images obtained with FRM depends on the receiver band and the diameter of the
field of view. Table A-7 shows examples of the time cadence for several combinations of observing bandand field of view.
• In order to flux calibrate solar images obtained with FRM, it is assumed that the field of view includes aquiet region and that the brightness during the observation does not vary significantly. Hence, PIs shouldcarefully select the FRM field of view, considering these assumptions, and may wish to justify their choicein the proposal. When there is no quiet region in the field of view the precision of the flux calibration
may be compromised and Quality Assurance Level 2 may fail, but the observation will not be repeated.
• Proposers will specify their solar target by providing a target position in Heliocentric coordinates. The
ALMA Observatory will coordinate with successful PIs to get an updated target position at least 24 hours
in advance of the proposed observation. The interaction will be done via the Helpdesk. The ALMA Solar
Ephemeris Generator tool is available for PIs to help them generate the ephemeris.
• Only proposals for continuum observations in Bands 3, 5, 6 and 7 will be accepted. For interferometricobservations, these will be obtained using the low spectral resolution (TDM) mode (see Section A.6.1).

47

FOV DiameterBand 3

Band 5 and Band 6

Band 7100 arcsec

n/a1

11 sec14 sec200 arcsec

13 sec21 sec27 sec

300 arcsec

19 sec32 sec40 secTable A-7: Time cadence of images obtained with FRM.
1100” is comparable to the size of the Band 3 primary beam (60”) Hence, such a field of view is not suitable
for FRM.
The individual integration times for this mode are fixed to 1 second, and the frequencies are fixed tofour 1875 MHz-wide spectral windows centered on the frequencies shown in Table A-6. The high spectral
resolution (FDM) observing mode is not offered for solar observations.
• The observing frequencies of the Total Power observations are as shown in Table A-8, but the Total Powerdata only include one channel per spw; a correlator will not be used for Total Power observations so
autocorrelation measurements will not be available.
Band

spw1

spw2

LO1

spw3

spw4

(GHz)

(GHz)

(GHz)

(GHz)

(GHz)

3

93.0

95.0

100.0

105.0

107.0

5

191.0

193.0

198.0

203.0

205.0

6

230.0

232.0

239.0

246.0

248.0

7

339.6

341.6

346.6

351.6

353.6

Table A-8: Observing frequencies for Cycle 10 solar observations. This table assumes that each baseband ispopulated with a single spectral window (spw) centered on the baseband frequency.
• Simultaneous observations with Bands 3, 5, 6 and 7 are not offered: each Science Goal can only include
one band.
• Observations may be performed using dual linear polarization (XX, YY) or single polarization (XX)correlations in Bands 3, 5, 6, and 7. Full polarization measurements (XX, YY, XY, YX) are offered onlyin Band 3 with the 12-m Array. The 7-m antennas are not useful for full-polarization observations.
• While TP Array observations will be carried out simultaneously with the interferometric observations,
TP Array observation will be performed using dual linear polarization (XX, YY), even in the case of fullpolarization 12-m observations.
• For polarization observations, we recommend multi-pointing observations with small spacing (e.g., using
the mosaic observing mode) for use in evaluating the effect of beam squint in Stokes-V maps, even if the PI
only needs the field of view obtained with a single-pointing. However, the accuracy of polarization maps
imaged as a mosaic with a wide field of view is not guaranteed by the ALMA observatory. Therefore, thefull-Stokes images for each pointing will be provided as separate QA2 products.
• Because the WVR receivers are saturated when the antennas point at the Sun, WVR corrections foron-source (solar) data are not possible (See Section 8.10.2 of the Technical Handbook).
• Absolute calibration of single-dish brightness temperatures is currently no better than ∼10% but is more
realistically ∼15% While efforts are on-going to improve solar calibration, Science Goals that require48

absolute temperatures more accurate than this, and in particular comparisons of absolute temperatures
between Bands 3, 5, 6 and 7, will be difficult to carry out successfully.

A.12

VLBI observations

Proposals will be accepted for VLBI observations that include ALMA as a phased array, with the following
capabilities and restrictions:• VLBI observations will be conducted in “campaign mode”, whereby specific dates are reserved for the
execution of VLBI programs in coordination with the other facilities in the VLBI network. This ensuresthat VLBI experts are available to help with program execution. To maximize phasing quality, observing
campaign windows are typically selected during the periods when the 12-m Array is in a relatively compact
configuration (with significant numbers of baselines ≤ 500 m; see configuration schedule in Table 3). The
GMVA observing dates in 2024 are expected to be 18 April – 23 April. The EHT observing dates have
not yet been fixed, but are anticipated to be in the March/April 2024 time frame.
• Standard VLBI observations perform phase-up of the array directly on the science target. This mode is
known as active phasing. To ensure an adequate SNR for the phase-solving algorithm actively phased
continuum targets must have a correlated flux density on intra-ALMA baselines (< 1 km baselines) of≥350 mJy (Band 1), ≥ 500 mJy (Bands 3 and 6), or ≥ 750 mJy (Band 7). For spectral line (emission line)
targets, array phase-up may be achieved using the line emission itself, provided that it is sufficiently bright.
As a guideline, active phasing is appropriate for spectral line targets whose peak line flux Flim,line (ν) meetsthe following criterion:pFlim,line (ν) ≥ Flim,c (ν) (234.4 MHz)/(Wl ) (Jy)where Wl is the linewidth (in MHz) of the spectral line peak and Flim,c (ν) is assumed to be, respectively,
0.35 Jy (Band 1), 0.5 Jy (Bands 3 and 6), or 0.7 Jy (Band 7).
• VLBI observations of faint science targets (i.e., with correlated flux densities less than the minimum
requirements for active phasing given above) require the use of passive phasing. Passive phasing may be
used for weak continuum sources, as well as for targets with spectral lines that are weak, broad, and/or thatare seen in absorption. To perform array phase-up in passive mode, the user must select a suitable phasing
calibrator (‘phasor’), ideally within an angular separation of ∼10 degrees (Band 1); ∼6 degrees (Band 3),
or ∼3 degrees (Bands 6 & 7), respectively. Typical passive phasing observing sequences will consist of ashort (∼1–3 min) VLBI scan on the phasor, immediately followed by a longer scan on the science target
itself (up to ∼5 min). Minimum flux density thresholds for the phasor depend on the observing band
and are identical to those for standard active phasing observations, as described above. The user-definedcalibrator interface is enforced for passive phasing and the default dynamic phase calibrator should be
replaced with the selected phasor as a fixed calibrator (see Section B.6.1). The choice of calibrator should
be justified in the Technical Justification.
• VLBI proposals for continuum mode observations will only be accepted for Bands 1, 3, 6, and 7. Theseobservations will be obtained in full polarization using the widest bandwidth FDM configuration of 64input Correlator (see Section A.6.1). The default observing frequencies for the band centers of the four1875 MHz-wide spectral windows are given in Table A-9. Starting in Cycle 10, observers may optionallychange these default frequencies. However, users must ensure that frequency selections are compatible
with the tuning restrictions of other peer VLBI observing sites that are expected to participate in theobservation. Prospective observers who are uncertain about the tuning restrictions of proposed GMVA
or EHT partner sites should contact the ALMA Helpdesk well in advance of the proposal deadline. In
addition, the bandwidth of each ALMA baseband is fixed at 1875 MHz (the maximum available) and use
of full polarization mode is required. For Bands 1 and 3, only a single baseband (the one including spw1)
will be recorded owing to recording rate restrictions at many of the GMVA partner sites. For Bands 6
and 7, all four basebands are recorded.
• Beginning in Cycle 10, spectral line VLBI observations are offered in Bands 1, 3, 6, and 7. For Bands 1 and
3, only a single baseband (the one including spw1) will be recorded for VLBI in spectral line experiments

49

Band

spw1

spw2

LO1

spw3

spw4

(GHz)

(GHz)

(GHz)

(GHz)

(GHz)

1

43.16841.16835.14545.16847.124

3

86.26888.26893.26898.328100.268

6

213.1

215.1

222.1

227.1

229.1

7

335.6

337.5414

342.6

347.6

349.6

Table A-9: Default observing Frequencies for Cycle 10 VLBI Observations. This table assumes that eachbaseband is populated with a single spectral window (spw) centered on the baseband frequency.
(see “Spectral line” in Section B.6 for additional details). For Bands 6 and 7, up to four basebands will
be recorded. The central frequency of each VLBI baseband may be flexibly tuned, but selection of the
ALMA FDM correlator mode with 1875 MHz bandwidth and full polarization is required, as it is the
only ALMA Baseline correlator mode that is compatible with operation of ALMA’s VLBI backend. The
proposer must also ensure that the adopted tuning can be matched at all participating observing sites.
Observers with questions about the tuning restrictions of prospective partner sites should contact the
ALMA Helpdesk. Any spectral windows not used for VLBI may be flexibly configured in the ALMA OT
with different tunings or spectral resolutions, subject only to ALMA’s standard tuning restrictions.
• Proposers are required to enter a VLBI total time requested. Here, they should enter the amount oftime requested for ALMA (and not the total time requested to the GMVA/EHT networks, which may
be longer). Note that this time must include overheads. For ALMA + GMVA or ALMA+EHT the total
observing time (including overheads and ALMA calibrations) is a factor of four times the expected time
on source (i.e., a 25% duty cycle). In cases where additional GMVA or EHT network time is requested
beyond the nominal ALMA+GMVA or ALMA+EHT time request, the PI should explicitly note this in
the Technical Justification.
• If multi-epoch observations are requested, they must fit within the contiguous ∼5 day ALMA+GMVA
observing window or the two-week ALMA+EHT window, respectively, and the total time request must
be the aggregate time of all observations.
• GMVA and EHT sites record data on a circular polarization basis, while ALMA records linear polarization
products. The total duration of the project (including overheads) must span a minimum of three hours
to ensure that the parallactic angle coverage of the polarization calibrator is sufficient for accurate linearto-circular polarization transformation of the ALMA VLBI data.
For 7 mm and 3 mm VLBI (both spectral line and continuum experiments), a proposal must have been submitted
to the GMVA network by their 1 February 2023 deadline (see the GMVA website). The GMVA web site also
provides a sensitivity calculator. Another sensitivity calculator is available at the European VLBI Network site.
For all 1.3 mm and 0.87 mm proposals, the JAO will forward the submitted proposals to the EHT network
for technical assessment. Thus proposers do not need to send their proposal to the EHT directly. Technicalassessment of GMVA proposals is also performed as part of the normal GMVA proposal review process.

A.13

Phased Array observations

The 12-m ALMA dishes may be used as a stand-alone phased array, where signals from individual antennas are
summed after phase alignment (i.e., so that the array functions like a large single-dish telescope). Currently,
use of this mode is restricted to pulsar science. Starting in Cycle 10, this Phased Array mode is available inBands 1, 3, 6, and 7. As these are ALMA-only observations, the proposal should not be sent to the GMVA.
• This mode is available by selecting the Phased Array proposal type. In Cycle 10, only pulsar science50

projects will be accepted for this mode, so the PI should select the scientific keyword “Pulsars and neutronstars” in the scientific category “Stellar Evolution and the Sun”. The proposal code will have the “.P”
suffix.
• The capabilities are similar to those currently available for continuum VLBI, i.e., a single source per
Science Goal with a maximum-bandwidth, pseudo-continuum spectral setup. The default spectral window
frequencies for each band are the same as those for VLBI (Table A-9).
• As for the standard VLBI continuum modes, VLBI recordings of the phased sum signal are made while
the ALMA interferometric data are archived in parallel.
• Since this mode is limited to observations of pulsars, which are generally faint at mm wavelengths, use ofpassive phasing (see Section A.12) is enforced by the ALMA OT. The choice of a fixed phase calibrator(‘phasor’) will need to be made and justified (see Section B.6.1).
• Typical passive phasing observing sequences will consist of a short (∼1–3 min) VLBI-type scan on thephasor (during which phasing solutions are computed and applied), immediately followed by a longer,
VLBI-type scan on the science target itself, during which no phasing calculations are performed (up to∼5 min, depending on the band).
• The phased-array data from all four available basebands (derived from the VLBI recordings) will be madeavailable to the PI in PSRFITS format.
• Observations using this mode will be scheduled during the time periods assigned for VLBI. For Cycle 10
this is expected to be in March/April 2024.
• As for VLBI proposals, the total array time required for each Science Goal must be provided (see Section B.7). This should be set to a minimum of 3 hours to allow for robust polarization calibration. The
requested array time should be justified in the box entitled “Phased Array Technical Justification including
Post-Processing”.
• Contact your ARC through the Helpdesk for additional assistance in planning Phased Array mode observations.

51

B

Technical Justification guidelines

The Technical Justification must be entered directly into the ALMA OT for each Science Goal. Below are
guidelines on issues to consider in the different sections. Sections B.5, B.6, and B.7 point to specific items thatneed justification for solar, VLBI, and Phased Array (pulsar) observations, respectively. In general, PIs should
justify all the parameters requested in the ALMA OT.

B.1

Sensitivity

At the top of the sensitivity section, the ALMA OT will display the calculated sensitivity and S/N ratio achievedfor different bandwidths (bandwidth requested for sensitivity, aggregate bandwidth, a third of the linewidth)
as appropriate for the spectral setup and the defined Expected Source Properties. While the justification for
the requested sensitivity or S/N ratio should be included in the Scientific Justification (Section 5.3.2), the TJ
must explain which sensitivity or S/N ratio are expected for all the parts of the spectrum that are of interest,e.g., for a spectral setup targeting a weak and a strong spectral line as well as the continuum, and the meansby which the proposed technical setup will achieve those requests.
The fluxes in the Expected Source Properties must be entered per synthesized beam; i.e., proposers may haveto correct any available flux measurements for the fact that the requested source is spatially resolved by ALMA
and the flux is distributed over several synthesized beams (see Knowledgebase articles “How can I estimate thePeak Flux Density per synthesized beam using flux measurements in Jy or K from other observatories?” and“How do I convert flux measurements given in Jy km/s or K km/s into the peak flux density required by the
OT?” and this video for more details on using fluxes/brightness temperatures from other facilities).
Users should be aware that the sensitivity requested may not be achievable in practice if the observations are
dynamic-range limited; e.g., when the field of view contains another, very bright, source or the spectrum hasvery bright lines. S/N values smaller than three trigger a blue informative message and need to be fully justified;they may lead to a rejection of the proposal on technical grounds if no adequate explanation is given. For setups
including spectral lines, another value to double-check is the ratio of the linewidth (entered in the Expected
Source Properties) over the bandwidth used for sensitivity (from the Control & Performance editor), which isconveniently displayed by the ALMA OT. It is important to understand that the sensitivity requested will beachieved over a frequency bin corresponding to this bandwidth, not necessarily over every spectral resolution
element. For spectral-line measurements this value should normally be larger than three (or even higher if
you want to measure the shape of the line profile). An informative message will appear if this is not the case,and PIs should address this issue in the justification text (e.g., if the sensitivity requirement is driven by thecontinuum, it may be acceptable to have a very low ratio).
The final parameter to be checked for observations measuring both line and continuum emission is the spectral
dynamic range, defined as the continuum peak flux divided by the line rms. Limits on the spectral dynamic
ranges offered in Cycle 10 for the different ALMA bands are given in Section A.9.3; an informative message willappear in the ALMA OT if these are exceeded and the proposal may be rejected on technical grounds unlessjustified. The spectral dynamic range is important especially when trying to detect a weak line on top of astrong continuum, and high spectral dynamic ranges may require a better bandpass accuracy than possible witha standard calibration. If a high spectral dynamic range is required, extra bandpass calibrations may need tobe obtained selecting “User-defined calibration”.
Please note that if a spectral window using a 4x4 bit mode is set as "Representative" in the ALMA OT, thesensitivity will increase by 12% with respect to the 2x2 bit mode with the same spectral resolution, and therequired on-source time will be reduced accordingly.

B.2

Imaging

When planning ALMA observations, the complexity of the emission in the science target field should be considered, in addition to the sensitivity goals. In this section, proposers should justify their AR and MRS requests on
the basis of the field’s complexity and their scientific goals. An interferometer’s ability to reconstruct complex
emission is directly related to the uv -coverage of the data. The AR and MRS needed to image complex emission

52

should be carefully justified (if necessary, using simulations), especially if multiple antenna configurations are
required. Proposers should also consider the overall uv -coverage of their observations as this directly impacts
image fidelity, particularly for snapshot observations (see Chapter 3 of the Technical Handbook). The numberof required antenna configurations is listed in the observing time estimate of the project time summary in the
ALMA OT.
The “snapshot” (i.e. short observation) uv -coverage is excellent for the compact ALMA 12-m Array configurations C-1 to C-3 and still reasonably good for C-4 to C-6, but for the longer baseline configurations, C-7 to C-10,
it is quite sparse even with 50 antennas (see Section 7.5 of the Technical Handbook). Therefore, more observing
time must be spent to “fill in” the missing uv -coverage, as much as possible. Thus, high fidelity imaging ofcomplex and/or high dynamic range emission may require a longer observing time than implied by sensitivity
requirements alone, and this is especially true for the long-baseline configurations. Consecutive executions ofa given SB (if needed) are favored during scheduling to maximize uv -coverage. Nonetheless, if more extensive
uv -coverage is required to satisfy the imaging requirements, the ALMA OT’s sensitivity-based time estimate
can be overridden (see below). PIs are strongly encouraged to use the ALMA simulator tools to assess thepotential need for extra uv -coverage.
For single pointings with the 7-m Array, integrations of at least one hour are recommended to achieve good
image quality. Ensuring sufficient uv -coverage for mosaics with the 7-m Array can be problematic because theintegration time is spread out over many pointings; for this case, simulations that assume the minimum numberof guaranteed antennas are strongly encouraged to help set the per-pointing integration time. See Section 7.7of the Technical Handbook for more details.
For single or non-overlapping pointings, the source should fit within the inner one third of the primary beam(field of view), or the PI should discuss the effects of the sensitivity loss towards the beam edges.
PIs should also pay attention to the expected image dynamic range (see Section A.9.1) if attempting to detect aweak signal that falls in the same pointing as a much brighter source. The ALMA OT cannot identify such cases
automatically since it has no knowledge of the flux structure of the field to be observed. See the Knowledgebase
article “What is meant by imaging dynamic range?” for details.

B.3

Correlator configuration

For spectral-line observations, the ALMA OT reports the number of (Hanning smoothed) spectral resolution
elements per linewidth, taking into account any spectral averaging, and the width of the representative spectral
window. PIs have to make sure to select the correct representative spectral window. If the spectral resolution islarger than one third of the linewidth from the Expected Source Properties, an informative message will appear,
and if not suitably justified this will lead to the rejection of the proposal on technical grounds. Note that the
spectral resolution is not necessarily the same as the bandwidth for sensitivity.
The requested correlator setup and the placement of spectral windows should be carefully justified in the freeformat text box. In the case of multiple spectral lines and/or narrow spectral windows in particular, PIs should
double-check that the line profiles are fully covered by the selected spectral windows.
PIs should also check whether any of the spectral windows are severely impacted by atmospheric absorption,
which can affect Bands 5 and 7 to 10 especially. If necessary, the representative frequency should be modified
to be at the most restrictive part of the atmosphere where a line needs to be detected, thus impacting the time
estimate. Any continuum windows should be moved to avoid areas of reduced transmission.
Selection of a 4x4 bit mode instead of a 2x2 bit mode will limit the bandwidth accessible to a given spectral
window (when compared with the 2x2 bit mode). In cases where several spectral lines are expected to be
included in the spectral window, the PI should clearly justify that they will all be included within the reduced
bandwidth of the 4x4 bit mode.
For the double sideband receivers (Bands 9 and 10), the atmospheric transmission in the mirrored spectral
window due to the 90-degree Walsh Switching (Section A.5) impacts the sensitivity achieved in the spectral
window and therefore the time estimate. PIs may wish to modify the spectral setup accordingly. The bestpractice for good calibration is to add continuum spectral windows in any unused basebands, in particular for53high-frequency SGs. The Phase 2 Group assigned to the project can add these windows, if needed.
For sources with known high line density (∼ 1 spectral feature per 10 MHz), PIs are particularly encouraged
to set up all the spectral windows in FDM mode. This will allow a more robust determination of the line-freechannels used to form the aggregate continuum during data processing and imaging.

B.4

Choices to be justified

The ALMA OT will automatically catch a number of user choices that must be explicitly justified in a text box.
These choices are:• Override of ALMA OT’s sensitivity-based time estimate: Proposers may wish to override the ALMA OT’stime estimate to monitor a source over a certain time range or to build up the uv -coverage for imaging
a complex source. When using this option, proposers should keep in mind that programs that require
more than two hours of continuous observations cannot be guaranteed due to variable weather conditions
and system interruptions (Section A.10). The time entered refers to that of the largest array requested,
includes all calibrations, and must be fully justified. Note that the ALMA OT assigns the PWV basedon the representative frequency of the requested observations and the declination of the source to ensure
data quality. Thus, it is not possible to request specific weather conditions for the observations.
• Time-constrained observations: the ALMA OT allows you to specify two types of time-constrained observing: single visit and multiple visits. In the first case, one or more time windows are specified, but theobservations will only be carried out once during any of these time windows. In the second case, the Science Goal is observed in each of the time windows specified. The technical feasibility of time-constrained
observations will be decided on a case-by-case basis.
• User-defined calibration: the default system-defined calibration option ensures that the proper calibrations
for the flux scale, bandpass, and relative antenna gains are obtained. Observations making use of the fullpolarization capabilities of ALMA will also include the necessary calibrations by default. User-definedcalibrations should be necessary only in rare cases, e.g., if a very high spectral dynamic range is required,it may be necessary to perform additional calibrations and/or use specific sources. Such requests must
be explained and justified in detail. Programs that cannot be calibrated or that significantly increase thecomplexity of data reduction will not be allowed and will be flagged as technically infeasible and rejected.
• Low maximum elevation: sources that transit at a low elevation are difficult to schedule for observation
since they suffer from high atmospheric attenuation and require low PWV, especially at high frequencies(see Section A.8). A detailed explanation should be provided as to why these sources need to be observed
rather than sources at higher elevation.
• Single polarization: this should only be used when the highest spectral resolution is required, as thesensitivity achieved is lower than when using the default dual polarization. PIs should carefully justify
why the high spectral resolution requested is required.
√• Sparser sampling than the default λ/ 3D (Nyquist sampling) can be more effective at covering large areas
more quickly, at the price of non-uniform spatial coverage and noise. Deviating from the default mosaic
sampling must be justified scientifically, and is to be avoided when imaging extended sources, particularly
if image fidelity is an important concern.
• Enhanced positional accuracy: this option should be selected when an astrometric accuracy better than
nominal is required (see Section A.9.5). In the corresponding Technical Justification section, the PI mustjustify the need for the enhanced positional accuracy and give any further details that may have beenadvised by ALMA staff through the Helpdesk.

B.5

Solar observations

The sensitivity calculator is not adequate for solar observations because the antenna temperature greatly exceeds
the system temperature and, moreover, depends on the solar target (e.g., quiet Sun, active region, solar limb).
Therefore, solar proposers are asked to enter the total time and justify this request to the extent that depends
on technical imaging considerations, not on scientific factors. For example, for a mosaic of a target in a given

54

frequency band, PIs should indicate how many repetitions of the sampling pattern are needed and why. For
this calculation PIs should take into account that ALMA observations are comprised of one or more executionsof an SB. The total execution time of an SB cannot exceed 2 hours, which will include the time overheads forbandpass and flux calibration. These calibration overheads amount to about 25 minutes.

B.6

VLBI observations

B.6.1

Continuum

The VLBI Technical Justification should be tuned to the overall science goals. The ALMA Technical Justification
should include a justification of the need for ALMA, the reasons for using the selected band (Band 1, 3, 6, or
7), the flux density of the target on a 1 km baseline, expected correlated flux density on baselines longer
than 5000 km, the total observing time requested (including time for calibration), and potential bandpass,polarization, and delay calibrators. If polarimetry is requested, the expected SNR for the polarized emission
should be stated. If imaging is requested, imaging considerations should also be mentioned (e.g., dynamic range
issues or complex source structure), along with any other special technical requirements. Finally, the proposer
should specify the particular EHT or GMVA stations that are requested as part of the VLBI array.
The following online material is currently available to help justify the requested observing time:• At 3 mm: the sensitivity calculator and the 3 mm VLBI page.
• At 1.3 mm: the 1 mm VLBI page.
Information is also available at those sites for planning 7 mm and 0.87 mm proposals.
Observations of VLBI targets with correlated flux densities on intra-ALMA baselines out to 1 km that are< 0.35 Jy (Band 1), < 0.5 Jy (Band 3 or 6), or < 0.75 Jy (Band 7) require the use of “passive” array phasing.
Passive phasing may also be used for certain types of spectral line experiments (see Section A.12). Passive
phasing requires selection of a suitable phase calibrator (termed a ‘phasor’). The suitability of the selected
phasor must be justified on the basis of its flux density, source structure, and proximity to the VLBI target.
ALMA’s phasing algorithm currently assumes that the phasor is a point source located at the phase center.
Therefore sources with complex structure on short baselines are typically not suitable for use as phasors. In
addition, during each phasing scan the ALMA antennas must be slewed to place the phasor at the center of the
field-of-view; the ability to apply phasing corrections derived sources within the primary beam but offset fromthe phase center is not currently implemented.
There are two ways to search for a phasor candidate: directly from the ALMA OT, or through an initial searchon the web-based ALMA Calibrator Source Catalogue.
Searching for a phasor source in the ALMA OTWhen proposing a Phased Array project or VLBI-mode observation of weak targets (as defined in Section A.12)
the “User-defined calibration” option is triggered in the “Calibration Setup” editor. There, in the “Goal Calibrators” panel, one will see four calibration type entries. To select a phasor source, the PI should follow thesesteps:• Select the “Phase” entry and click on “Delete Selected Calibration”;• Click on “Add Fixed Calibrator”, select “Phase” in the pop-up window, and click “Create”;• Select “Sidereal Target” and click on “Select from Source Catalogue...”;• Set the “Radius (◦ )” value of the “Cone Search” to 10◦ for Band 1; 6◦ for Band 3; or 3◦ for Band 6 or 7
(suggested values);• In “Flux”, set "Min" to 0.35 Jy (Band 1), 0.5 Jy (Band 3 or 6), or 0.75 Jy (Band 7) and click on "Submit
Query";• Ideally, select the entry with the highest “Flux Density”, and with empty “UV Min/Max” columns.
Searching for a phasor source in the ALMA Calibrator Source Catalogue55

In the “Query Form” tab of the web interface, the RA and DEC information of the science target should beentered in the “Position” box. The suggested settings for the search radius are 10◦ for Band 1, 6◦ for Band 3,
and 3◦ for Bands 6 or 7. In the “Energy” box, "Flux Density" should be set to “>0.35” (Band 1), “>0.5” (Bands
3 and 6), or “>0.75” (Band 7). “Band” should be set to “3” for Band 3 observations, “7” for Band 7 observations,or “1,3,6,7” for observations in any other band. The reason for this recommendation is that ALMA’s flux checkobservations are more frequently executed in Bands 3 and 7, and less often in other bands. Hence, to retrievea more contemporaneous flux value in case a direct measurement is not available, one can interpolate to thedesired observing band.
After clicking on the “Search” button, the “Result Table” will provide a list of phasor candidates. In casethere is a need to interpolate to estimate a flux density in the observing band of interest, the PI can use the“getALMAflux” task from the Analysis Utils (which must be installed within CASA). The PI can also use the“Result Plot” for assessment, where pressing a given data point in the RA/DEC plot on the left-hand side will
trigger a light curve plot to appear on the right-hand side. The PI should then provide the identified sourcein the “User-defined calibration” option (see above). Be aware that if the flux of the selected phasor decreases
below the minimum flux density thresholds near the time of the expected observation execution an alternative
source will have to be found in coordination with the Phase 2 Group.
What if no sufficiently bright phasor candidate is found?
Identified phasor sources will likely be variable, so it may be difficult to predict at the time of proposal submission
what the flux will be during the observation. If a given candidate source is fainter than the recommended(band-dependent) flux density threshold at the time of proposal submission, but its light curve (available in the
ALMA Calibrator Source Catalogue; see above) shows that it has been brighter in the past or has a rising flux
potentially increasing above the threshold, the PI can propose that source as a phasor. In this case, PIs may
wish to include a justification in the proposal and JAO will check the source’s flux closer to the VLBI campaign
run. The project will be executed only if the selected source is observed to have a flux density sufficient forsuccessful array phase-up at the time of schedule preparation (roughly 2 months prior to observation).
What if no phasor candidate is found within the suggested search radius?
If the proposed phasor source lies at a projected separation of more than 10◦ from a Band 1 target, ≥ 6◦ froma Band 3 target, or ≥3◦ from a Band 6 or 7 target, there are additional considerations that should be taken
into account. The guidelines for angular separation are based on observational conditions during a time of
the year (March/April) when VLBI campaigns are usually run. These conditions imply, for example, that thephase rms induced by atmospheric turbulence is likely to be up to ∼ 25◦ (84% probability) for the characteristic
phasing radius in Band 3 and up to ∼ 45◦ (84% probability) in Band 6. Assuming a maximum acceptablesignal decorrelation of ∼20%, Figure 10.8 in the Technical Handbook leads to the recommended maximum
phasor separations noted above. In general, the farther from the target the phasor lies, the higher the expectedsignal decorrelation losses owing to differing atmospheric lines-of-sight for phasor and target, as well as longer
slew overheads (during which the atmosphere may change, particularly at high frequency). Note that there are
significant limits to how much QA2 analysis can compensate for these decorrelation losses in post-processing,and this will depend in part on whether the schedule allows for a robust gain solution interpolation between
scans. In extreme cases, the flux calibration will become highly uncertain because of the loss in correlated
amplitude. Considering these issues, the PI can still propose a phasor that is farther way than the guidelines
suggest, but it must be justified with regard to how it is likely to impact the data quality and whether thescience goals can still be achieved.
B.6.2

Spectral line

For spectral line experiments the ALMA Technical Justification should include a justification of the need for
ALMA, as well as a description of the properties of the spectral line of interest, including: rest frequency,
expected peak line flux on a 1 km baseline, peak brightness temperature, anticipated correlated flux density on
a 5000 km baseline, LSR velocity of line peak, and total line width (in km s−1 ). The Technical Justification
should also specify the total observing time requested (including time for calibration). If imaging is requested,imaging considerations should be described (e.g., dynamic range issues or complex source structure), along withany other special technical requirements. Lastly, the best available coordinates and proper motion of the line

56

target should be specified.
A caution regarding target coordinate specification for spectral line VLBI : the field-of-view of the phased arraybeam is effectively limited to the size the synthesized beam of the ALMA array. Because many Galactic sources
have significant proper motions, it is essential that these corrections to the target position be accounted for;
failure to do so may result in the target falling outside of the phased array beam and a complete loss of thedata. Note also that the procedure for specification of proper motion corrections is different for VLBI thanfor standard ALMA observations. In general, VLBI observations require that the J2000 coordinates of thesource include the proper motion corrections appropriate for the epoch of the observation. These PI-specified
coordinates will be used directly in the VEX files at all participating sites, including ALMA, and any otherproper motion corrections will be zeroed during the observation.
The VLBI Technical Justification for spectral line experiments should describe the overall science goals andshould specify the list of GMVA stations being requested. A list of candidate VLBI bandpass, fringe-finder,
and polarization calibrators should be indicated, as well as the requested VLBI correlator set-up.
Unlike continuum experiments, which use a default VLBI correlation set-up, spectral line experiments allow
the PI some flexibility in specifying details of the correlation output, subject to certain restrictions owing todata volume considerations and human resource limitations at the VLBI correlators. Particulars of the VLBI
correlation set-up requested should therefore be described in the Technical Justification, including: (i) spectral
resolution (in multiples of 15.625 kHz); (ii) frequency center of the correlation passband; (iii) total correlated
bandwidth (≤ 128 MHz); and (iv) time resolution (in multiples of 512 milliseconds). By default, all four Stokes
products will be delivered for all experiments. At minimum, the requested total bandwidth should be sufficient
to include all line emission from the target as well as a number of line-free channels (e.g., ∼ 20% of the totalband). Details of the correlation set-ups are rather involved and an exact match to the specifications proposedby the PI may not be possible in all cases. Owing to limited resources at the VLBI correlators, for Cycle 10 a
maximum of two correlator passes will be allowed per project. Proposers are encouraged to consult the Helpdesk
if they are uncertain about the optimum specifications for their science needs.
As noted in Section A.12 , in order for array phase-up to be performed during observations of spectral line
targets, it is necessary that the line target have a sufficiently large peak flux density on intra-ALMA baselines
to ensure robust performance of the phasing system. Because nonthermal (maser) emission lines are often
time-variable, it may be impossible to know whether a particular source will meet this criterion at the time of
Cycle 10 VLBI session. In such cases proposers may request that JAO perform a test observation a few weeks inadvance of the scheduled VLBI session to verify the line flux density of the primary target. Spectral line targets
not meeting the flux density requirements for active phase-up may instead be observed using passive phasing(see Section A.12), provided that the penalty in additional overheads does not preclude achieving the scienceobjectives and that the science target has not become too weak to detect on global baselines. Alternatively, forline sources with sufficiently strong and compact continuum emission, active array phase-up may be performed
using the target’s continuum emission.

B.7

Phased Array observations

Proposers should first read the Phased Array mode sections of the ALMA Cycle 10 Technical Handbook, paying
particular attention to the items discussed in the “Technical Justification” portion of these sections. As passive
phasing is enforced for this mode, the choice of a fixed phase calibrator (‘phasor’) must be made and justified.
Additional inputs are also required to construct the Scheduling Block and these should be provided in the text
box titled “Phased Array Technical Justification including Post-Processing”:• Total observing time requested. To cover a sufficient parallactic angle range on the polarization
calibrator, typically ∼ 3 hours are required. However, the proposer should indicate how much time isneeded on target for the analysis (see below).
• The pulsar period (if known). This value should be provided so that the cadence of the correlator
subscans (multiples of 1.008s) does not interfere with the pulsar signal.
• Time resolution. The time resolution of the PSRFITS file must be a multiple of 8 µs; if lower time
resolution is adequate, this should be specified to avoid larger than needed PSRFITS files.

57• The polarization of the PSRFITS data product. The proposer can select from total intensity, dual
polarizations (XX and YY), coherence product, or full Stokes.
A caution on target coordinate specification for Phased Array observations: the field-of-view of the phased arraybeam is effectively limited to that of the synthesized beam of the ALMA array. Because many Galactic pulsars
have significant proper motions, it is crucial that these corrections be applied to the target’s J2000 coordinates
when setting up the observations. The procedure for specification of proper motion corrections is different for
Phased Array observations than for standard ALMA observing; specifically, Phased Array observations requirethat the J2000 coordinates of the source include the proper motion corrections appropriate for the epoch of theobservation. These PI-specified coordinates will be adopted directly in the VLBI schedule used to execute theobservations and no other proper motion corrections will be applied by the online system.
Computing the required array time for pulsar observations When in Phased Array mode, the digitizedvoltage signals from each ALMA antenna of the phased array are phase-adjusted and added to provide the phased
signal that is recorded. This process is done for each polarization, and the phased array includes most, but
not all, available antennas. This is different from the interferometric signal that results from the correlated
voltage signal from each antenna. On top of that, pulsar observations aim to detect the flux of a pulsed signal
rather than a continuous one. As a result, neither the sensitivity calculator within the ALMA OT nor the webinterface provide the correct sensitivity for phased-array pulsar observations. To compute the required totalarray time for pulsar observations, one should start by computing the time on source (Tint , in hours) following
the formula in Appendix A1.4 in the Handbook of Pulsar Astronomy (Lorimer & Kramer 2004), which may be
expressed as:
Tint [h] =W
2× SEFD2 / rms2 × Np × Nsp × ∆f × ηeff
/ 3600P −W

Here, W is the pulse width; P is the pulse period (typical values are W = C ∗ P where C=0.05 to 0.1); the
SEFD for 37 phased antennas is 40 Jy (Band 1), 69 Jy (Band 3), 97 Jy (Band 6), or 160 Jy (Band 7); rms is
the requested noise level (in Jy); Np is the number of polarizations and should be set to 2; Nsp is the requested
number of spectral windows; ∆f is the bandwidth of each correlator quadrant in Hz (1.875e9 Hz for the present
ALMA Baseline Correlator), and η eff is the end-to-end passive-phasing efficiency of ∼ 0.74.
To estimate the total required observing time on source (including overheads), the user should multiply thecomputed Tint by three9 . The result is the value the PI should provide in the ALMA OT. Note, however, thatto ensure reliable polarization calibration of the data, the total observing time specified should never be lessthan 3 hr.

B.8

Band-to-band Calibration

There is no additional technical justification required if a science goal using high-frequencies triggers the B2B
mode. All additional calibrations and overheads are included automatically by the ALMA OT.

9 This overhead factor is smaller than for the VLBI case because VLBI observations require the observation of specific calibratorsthat are not needed for pulsar observations.

58

C

Acronyms and abbreviations

2SB
ACA
ACD
ALMA
ANID
AOS
APEX
ARC
ARP
APRC
AR
ASC
ASIAA
AUI
B2B
BWSW
CASA
Co-I
Co-PI
CS
DDT
DGC
DSB
EA
EHT
EHTC
EPO
ESO
EU
FDM
FOV
GMVA
IF
KASI
JAO
LAS
LO1
LSRK
LST
MOST
MRS
NA
NAASC
NAOJ
NINS
NRAO
NRC
NSC
NSF
OSF
OST
OT

Dual-sideband
Atacama Compact Array
Amplitude Calibration Device
Atacama Large Millimeter/submillimeter Array
Agencia Nacional de Investigación y Desarrollo
Array Operations Site
ALMA Pathfinder EXperiment
ALMA Regional Center (for EA and NA) or Centre (for EU)
ALMA Review Panel
ALMA Proposal Review Committee
Angular Resolution
ALMA Sensitivity Calculator
Academia Sinica Institute of Astronomy and Astrophysics
Associated Universities, Inc.
Band-to-band
Bandwidth Switching
Common Astronomy Software Applications
Co-Investigator
Co-Principal Investigator
Contact Scientist
Director’s Discretionary Time
Differential Gain Calibration
Double-sideband
ARC East Asian ALMA Regional Center
Event Horizon Telescope
Event Horizon Telescope Consortium
Education and Public Outreach
European Organisation for Astronomical Research in the Southern Hemisphere
ARC European ALMA Regional Centre
Frequency Division Mode
Field Of View
Global Millimeter VLBI Array
Intermediate Frequency
Korea Astronomy and Space Science Institute
Joint ALMA Observatory
Largest Angular Structure
Local Oscillator 1
Kinematic Local Standard of Rest
Local Sidereal Time
Ministry of Science and Technology in Taiwan
Maximum Recoverable Scale
ARC North American ALMA Regional CenterNorth American ALMA Science Center
National Astronomical Observatory of Japan
National Institutes of Natural Sciences
National Radio Astronomy Observatory
National Research Council of Canada
National Science Council of Taiwan
National Science Foundation
Operation Support Facility
Observation Support Tool
Observing Tool

59

OUS
PDF
PI
PWV
QA2
SB
SCO
SG
S/N
SnooPI
SP
spw
TDM
TJ
ToO
TP
VLBI
WVR

ObsUnitSet
Portable Document Format
Principal Investigator
Precipitable Water Vapor
Quality Assurance Level 2
Scheduling BlockSantiago Central Office
Science Goal
Signal-to-noise
Snooping Project Interface
Science Portal
Spectral window
Time Division Mode
Technical Justification
Target of Opportunity
Total Power
Very Long Baseline Interferometry
Water Vapor Radiometer60

D

Science categories and keywords

The list below presents the available science categories and the corresponding keywords that can be used in the
ALMA OT to further specify the scientific area of the proposal. Proposers must select at least one and at most
two keywords.
Category 1 – Cosmology and the high redshift universea. Lyman Alpha Emitters/Blobs (LAE/LAB)
b. Lyman Break Galaxies (LBG)
c. Starburst galaxies
d. Sub-mm Galaxies (SMG)
e. High-z Active Galactic Nuclei (AGN)f. Gravitational lenses
g. Damped Lyman Alpha (DLA) systems
h. Cosmic Microwave Background (CMB)/Sunyaev-Zel’dovich Effect (SZE)
i. Galaxy structure & evolution
j. Gamma Ray Bursts (GRB)k. Galaxy Clusters
Category 2 – Galaxies and galactic nuclei
a. Starbursts, star formationb. Active Galactic Nuclei (AGN)/Quasars (QSO)
c. Spiral galaxies
d. Merging and interacting galaxies
e. Surveys of galaxies
f. Outflows, jets, feedback
g. Early-type galaxies
h. Galaxy groups and clusters
i. Galaxy chemistryj. Galactic Centers/nuclei
k. Dwarf/metal-poor galaxies
l. Luminous and Ultra-Luminous Infra-Red Galaxies (LIRG & ULIRG)
m. Giant Molecular Clouds (GMC) properties
Category 3 – ISM, star formation and astrochemistrya. Outflows, jets and ionized winds

61

b. High-mass star formationc. Intermediate-mass star formationd. Low-mass star formatione. Pre-stellar cores, Infra-Red Dark Clouds (IRDC)
f. Astrochemistryg. Inter-Stellar Medium (ISM)/Molecular clouds
h. Photon-Dominated Regions (PDR)/X-Ray Dominated Regions (XDR)
i. HII regions
j. Magellanic Clouds
Category 4 – Circumstellar disks, exoplanets and the solar systema. Debris disksb. Disks around low-mass stars
c. Disks around high-mass stars
d. Exoplanets
e. Solar system: Comets
f. Solar system: Planetary atmospheres
g. Solar system: Planetary surfaces
h. Solar system: Trans-Neptunian Objects (TNOs)
i. Solar system: Asteroids
Category 5 – Stellar evolution and the Sun
a. The Sun
b. Main sequence stars
c. Asymptotic Giant Branch (AGB) stars
d. Post-AGB starse. Hypergiants
f. Evolved stars: Shaping/physical structure
g. Evolved stars: Chemistryh. Cataclysmic stars
i. Luminous Blue Variables (LBV)
j. White dwarfs
k. Brown dwarfs
l. Supernovae (SN) ejecta
m. Pulsars and neutron stars
n. Black holeso. Transients

63