Science Highlight




ALMA Cycle 8 2021 Pre-Announcement

Following the postponement of Cycle 8 because of the COVID-19 pandemic, the Joint ALMA Observatory (JAO) will now start the next cycle of observations, referred to as "Cycle 8 2021", in October 2021. A Call for Proposals (CfP) with detailed information on Cycle 8 2021 is anticipated to be issued in March 2021 and the deadline for proposal submission will be in April 2021.  The purpose of this pre-announcement is to highlight aspects of the CfP to assist with early planning, and it includes newly updated information over the previous pre-announcement delivered for Cycle 8 in December 2019.  As the global response to the pandemic continues to evolve, we encourage interested parties to follow the ALMA Science Portal for the latest information.


General information


ALMA Cycle 8 2021 will start in October 2021 and span 12 months.  The JAO anticipates having 4300 hours for approved science observations on the 12-m Array and 3000 hours on the Atacama Compact Array (ACA), also known as the Morita Array.

The key dates (anticipated) for Cycle 8 2021 are:

17 December 2020

Cycle 8 2021 pre-announcement

17 March 2021

Release of the ALMA Cycle 8 2021 CfP and Observing Tool, and opening of archive for proposal submission

21 April 2021

Proposal submission deadline

August 2021

Results of the proposal review sent to proposers

8 September 2021

 ACA Supplemental Call for Proposals released, and opening of archive for proposal submission

1 October 2021

Start of Cycle 8 2021 observations

6 October 2021

Cycle 8 2021 Supplemental Call deadline


Proposal types in Cycle 8 2021 will include Regular, Very Long Baseline Interferometry (VLBI), Passive Phasing, Target of Opportunity, and Large Program.  VLBI proposals work in concert with the Global mm-VLBI Array (GMVA) or the Event Horizon Telescope (EHT).  GMVA programs must also submit a proposal to the GMVA by its 1 February 2021 deadline. Additional information about proposing with ALMA using the GMVA will be made available in the GMVA Call for Proposals in early January 2021. 

Antenna configurations for the main 12-m Array will be called C-1, C-2, and so on up to C-10, with C-1 having similar characteristics to the C43-1 configuration of Cycle 7, and likewise for the others.  Cycle 8 2021 will not include the two longest baseline 12-m Array configurations, C-9 and C-10.  Maximum baselines in Cycle 8 2021 will therefore be 8.5 km in configuration C-8.  Configurations C-9 and C-10 with maximum baselines of 13.9 km and 16.2 km, respectively, will again be available in Cycle 9.

In addition to the main Cycle 8 2021 CfP, the JAO will issue a Supplemental Call for proposals to use the ACA in stand-alone mode.  More information on the Supplemental Call is given below.


New in Cycle 8 2021


The following technical capabilities will be available this Cycle for the first time:

  • Solar observations in Band 5
  • A passive-phasing mode that allows observations of fainter VLBI targets¬†(Bands 3 and 6), and can also be used in an ALMA-only mode primarily for observations of pulsars¬†(Band 3). This mode can be used to observe sources with a correlated flux density < 500 mJy within an unresolved core on ALMA baselines up to 1 km, but requires there to be a bright calibrator close to the science target.
  • High frequency observations (Bands 9 and 10) with the stand-alone 7-m Array
  • Mosaicking of continuum linear polarization observations (Bands 3 to 7) with the 12-m Array
  • Spectral scans with the 7-m Array
  • Up to a total of 75 hours of full polarization observations of a single field with the 7-m Array in¬†stand-alone mode at the Main Call only


Updates to the Proposal Review Process


  • ALMA will adopt a distributed peer review process for scientific review of¬†most proposals submitted to Cycle 8 2021. After a successful pilot run in the Cycle 7 Supplemental Call (see¬†ALMA Memo 616), distributed peer review will be used for all¬†proposals requesting less than 25 hours on the 12-m Array, and ACA¬†stand-alone proposals requesting less than 150 hours on the 7-m Array.¬†In this review system,¬†for each submitted proposal the¬†PI (or one of the delegated co-Is) will be responsible for reviewing¬†up to¬†10 other submitted proposals, thus increasing the involvement of the ALMA community in the review process.
  • Large proposals and proposals requesting more than 25 hours on the 12-m Array will be reviewed by science review panels, as in previous cycles.¬†
  • ALMA encourages PIs to submit larger, more ambitious proposals.¬†Therefore, there is no longer a cap on the total time that can be allocated to Large Programs. Further, Large¬†Programs and proposals¬†that require more than 25 hours on the 12-m Array will have first priority to fill at least 10% of the observing queue. ¬†
  • All Cycle 8 2021 proposals will be reviewed using a dual anonymous¬†procedure.¬†¬†While proposers will still enter their names and¬†affiliations in the Observing Tool, their identities will be concealed from the reviewers.¬†¬†It will be the responsibility of the investigators to write their proposals such that anonymity is preserved.¬†¬†By using this procedure, we aim to minimize unconscious bias.¬†¬†Guidelines on preparing anonymous¬†proposals will be made available¬†prior to¬†the time of the CfP.

A FAQ on the proposal process is available here.


Technical Capabilities


The anticipated Cycle 8 2021 capabilities are:

Number of antennas

  • At least 43 antennas will be available from the 12-m Array
  • At least ten 7-m antennas (for short baselines) and three 12-m antennas¬†(for single-dish maps) will be available in the ACA¬†

Receiver bands

  • Receiver Bands 3, 4, 5, 6, 7, 8, 9 and 10 (wavelengths of about 3.1, 2.1,¬†1.6, 1.3, 0.87, 0.74, 0.44 and 0.35 mm, respectively)

12-m Array Configurations

  • Maximum baselines for the antenna configurations will vary from 0.16 km¬†to 8.5 km.¬†¬†Configurations C-9 and C-10 will not be offered in Cycle 8 2021.
  • Maximum baselines of 3.6 km for Bands 8, 9 and 10
  • Maximum baselines of 8.5 km for Bands 3 to 7

Spectral line, continuum, and mosaic observations 

  • Spectral line and continuum observations with the 12-m Array and the 7-m¬†Array in all bands
  • Single field interferometry (all bands) and mosaics (Bands 3 to 9) with¬†the 12-m Array and the 7-m Array
  • Single dish spectral line observations in Bands 3 to 8


  • Single pointing, on-axis, full, linear and circular polarization for both¬†continuum and full-spectral-resolution observations in Bands 3, 4, 5, 6,¬†and 7 on the 12-m Array.
  • Linear polarization imaging of a compact source on-axis in both continuum¬†and full spectral resolution modes is feasible at the level of 0.1%¬†(3 sigma) fractional polarization for the very brightest calibrators, and¬†0.2% (3 sigma) level for a typical observation.
  • The minimum detectable degree of circular polarization is 1.8% of the peak¬†flux for both continuum and full spectral resolution observations.
  • Mosaicking of continuum linear polarization observations (Bands 3 to 7) with the 12-m Array.
  • Single pointing, on-axis linear polarization observations with the 7-m Array in stand-alone mode (Bands 3 to 7). Note¬†that combined 7-m Array and 12-m Array polarization observations are¬†not supported this cycle.


Configuration schedule


The following table summarizes the anticipated configuration schedule. The table includes the start date of the configuration, the longest baseline, and the LST range with the best atmospheric stability, which is approximately from 2 hours after sunset to 4 hours after sunrise. The configuration schedule may be modified based on the Cycle 8 2021 proposal pressure.


Start date


Longest baseline

LST for best observing conditions

2021 October 1


8.5 km

~ 22‚ÄĒ10 h

2021 October 20


3.6 km

~ 23‚ÄĒ11 h

2021 November 10


2.5 km

~ 1‚ÄĒ13 h

2021 December 1


1.4 km

~ 2‚ÄĒ14 h

2021 December 20


0.78 km

~ 4‚ÄĒ15 h

2022 January 10


0.50 km

~ 5‚ÄĒ17 h

2022 February 1

No observations due to maintenance

2022 March 1


0.16 km

~ 8‚ÄĒ21 h

2022 March 26


0.31 km

~ 9‚ÄĒ23 h

2022 April 20


0.50 km

~ 11‚ÄĒ0 h

2022 May 10


0.78 km

~ 12‚ÄĒ2 h

2022 May 31


1.4 km

~ 13‚ÄĒ4 h

2022 June 23


2.5 km

~15‚ÄĒ6 h

2022 July 28


1.4 km

~17‚ÄĒ7 h

2022 August 18


0.78 km

~19‚ÄĒ8 h

2022 September 10


0.50 km

~20‚ÄĒ9 h



Large Programs


The definition of Large Programs, evaluation criteria, and scheduling constraints in a given LST range remain unchanged. Proposers should consider the expected amount of time available versus LST per configuration (see Figure 1) together with the scheduling constraints to calculate the amount of time available for Large Programs at a given LST and configuration.




Figure 1: Effective observing time available per configuration for executing PI projects.  For example, up to 36 hours are expected to be available in C-4 at LST 00 h for all observations and up to 18 h of those may be allocated to Large Programs. The total number of hours excludes time spent on observatory calibration, maintenance, reconfigurations, and other activities. 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. The data files containing these histograms are available here.


Stand-alone ACA Supplemental Call for Proposals


In Cycle 8 2021, ALMA will offer a stand-alone ACA Supplemental Call for Proposals.  The Supplemental Call will open on 8 September 2021 and the proposal deadline will be on 6 October 2021.  Observations from the Supplemental Call will be scheduled from January 2022 to September 2022.  The anticipated amount of time available will be announced in the Supplemental Call.  While stand-alone ACA proposals accepted from the Main Call may be assigned priority "A", "B", or "C", all accepted proposals from the Supplemental Call will be assigned priority "C".  Proposals submitted to the Supplemental Call will be peer reviewed through the distributed system.