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ALMA Cycle 4 Pre-announcement

Dec 14, 2015

The Joint ALMA Observatory (JAO) will start the next cycle of observing (Cycle 4) in October 2016. A Call for Proposals with detailed information on Cycle 4 will be issued in March 2016, with a deadline for proposal submission in April 2016. This pre-announcement highlights aspects of the Cycle 4 proposal call that are needed to plan proposals.


General information

ALMA Cycle 4 will start in October 2016 and span 12 months. It is anticipated that 3000 hours of 12-m Array science observations will be available for successful observations of approved projects. Observing time will also be available on the Morita Array (a.k.a. the Atacama Compact Array, or the ACA); the number of hours available on the ACA will be announced in the Call for Proposals. The remaining time on ALMA will be reserved for engineering, computing and scientific testing to extend and optimize ALMA capabilities.

The key dates for Cycle 4 are given below.

22 March 2016

Release of the ALMA Cycle 4 Call for Proposals and observing tool, and opening of archive for proposal submission

21 April 2016

Proposal deadline

August 2016

Result of the proposal review process sent to Proposers

October 2016

Start of ALMA Cycle 4 observations

September 2017

End of Cycle 4 observations


Anticipated Capabilities

Detailed information on the capabilities in Cycle 4 will be published in the Call for Proposals. The anticipated capabilities include:

Number of antennas

  • At least forty (40) antennas in the 12-m Array
  • Ten (10) 7-m antennas (for short baselines) and three (3) 12-m antennas (for making single-dish maps) in the ACA

Receiver bands

  • Receiver bands 3, 4, 6, 7, 8, 9, & 10 (wavelengths of about 3.1, 2.1, 1.3, 0.87, 0.74, 0.44, and 0.35 mm, respectively)

12-m Array Configurations

  • Nine configurations with maximum baselines from 155 m to 12.6 km; the planned configuration schedule will be released by 1 February 2016 and published in the Proposers Guide
  • Maximum baselines of 2.7 km for Bands 8, 9 and 10
  • Maximum baselines of 5.3 km for Band 7
  • Maximum baselines of 12.6 km for Bands 3, 4, & 6
  • Files containing representative antenna configurations for both the 12-m and 7-m Arrays suitable for CASA simulations are available from the ALMA Science portal ( tools/cycle4/alma-configuration-files).

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) polarization capabilities for continuum and full spectral resolution observations in Band 3, 6 and 7 on the 12-m Array

Cycle 4 observing modes will be classified as standard or non-standard. Standard modes have been well characterized and the observations are calibrated with the ALMA data reduction pipeline. Non-standard modes are not as well characterized and require manual calibration by ALMA staff.

Up to 20% of the observing time in Cycle 4 will be allocated to proposals requesting non-standard modes, which include:

  • Bands 8, 9 & 10 observations
  • Band 7 observations with maximum baselines > 2.7 km
  • All polarization observations
  • Spectral Scans
  • Bandwidth switching projects (less than 1GHz aggregate bandwidths over all spectral windows)
  • Solar Observations (see below)
  • VLBI observations (see below)
  • User-specified calibrations


New opportunities in Cycle 4

In Cycle 4, the following opportunities will be available to Proposers for the first time.

ACA stand-alone mode
Proposals will be accepted to use the ACA in a stand-alone capacity for spectral line (7m Array plus Total Power Array) or continuum (7m Array) observations.



Large Programs
Proposals will be accepted for Large Programs, defined as proposals that request more than 50 hours of observations with either the 12-m Array or the ACA in stand-alone mode. A Large Program should address strategic scientific issues leading to a breakthrough in the field, be coherent science projects not reproducible by a combination of smaller regular proposals, leading to high level archival data products, and contain a solid management plan ensuring an efficient utilization of the data, including analysis and organization of the efforts. Additional guidance on preparing Large Programs will appear on the ALMA Science Portal by 1 February 2016.

Millimeter-wavelength VLBI
Proposals will be accepted for Very Long Baseline Interferometry (VLBI) observations with ALMA in Bands 3 and 6 continuum (wavelengths 3 and 1.3 mm). ALMA VLBI proposals will be made in concert with an existing VLBI network: the Global mm-VLBI Array (GMVA) at 3 mm and a new NRAO/Event Horizon Telescope Consortium (EHTC) network at 1.3 mm. In addition to submitting an ALMA proposal, VLBI programs must also submit a proposal to the appropriate VLBI network according to their deadlines. Additional information about proposing with ALMA using these networks will be made available in mid-January 2016.

Solar observations
Proposals will be accepted for ALMA interferometric and single dish observations of the Sun at select frequencies in Bands 3 and 6.