Call for SMA Science Observing Proposals

This site is not currently open for submission of standard proposals. This previous call document is for reference only.

We warmly welcome submission of proposals for the upcoming 2021A semester. We actively solicit projects of all sizes, and we are particularly interested in increasing the number of smaller proposals that take just a few hours in time, projects that are especially time critical (such as coordinated observing campaigns and ToO triggered event programs) and require data in the coming several months, and in monitoring type proposals. SAO has access to 72% of the observing time on the SMA, which is allocated using an 'open skies' policy, while ASIAA (13%) and the University of Hawaii (15%) allocate to PIs eligible under their programs.

Information on the array and the submission process are provided below, and we are available to answer questions or point you to any information you may need. You may also view a PDF of an overview presentation given by TAC Chair Mark Gurwell on 19 February, 2021 here:

SMA Introduction and Proposal Information (2021A) (PDF)

Please contact us at sma [hyphen] propose [at] cfa [dot] harvard [dot] edu for questions on proposal preparation, observing techniques and strategies, observing control scripts, and data analysis.

Proposal Deadline
SMA Observing Time
Support for New Users
Number of Nights Available
Proposal Preparation
Proposal Evaluation
Accepted Proposals and SMA Observing

Proposal Deadline

The joint CfA-ASIAA SMA Time Allocation Committee (TAC) solicits proposals for observations for the period 2021 Jun 01 - 2021 Nov 15. Proposals must be submitted by:

Thursday, 4 March 2021, 11:00 HST (Hawaii)
Thursday, 4 March 2021, 16:00 EST (Cambridge, MA)
Thursday, 4 March 2021, 21:00 GMT
Friday, 5 March 2021, 05:00 CST (Taipei)

SMA Observing Time

The SMA is a joint project funded by the Smithsonian Astrophysical Observatory (SAO), one of two partners in the Center for Astrophysics | Harvard & Smithsonian (CfA), and the Academia Sinica Institute for Astronomy and Astrophysics (ASIAA) and also includes the Institute for Astronomy (IfA) at the University of Hawaii as a partner institution. The time allocation ratios for the three SMA partners, CfA:ASIAA:IfA, are 72:13:15. To promote excellence in scientific research and cooperation in the scientific community, the CfA follows an "open-skies" policy in allocating its share of the SMA time. Proposals from institutions worldwide are accepted for the CfA time and judged solely on scientific merit.

In addition to regular proposal programs, SMA offers opportunity for large-scale projects needing observing time in the range of 100 to 1000 hours. As a result, if a large-scale project proposal is successful, the time available for regular projects will be reduced. Proposers should refer to Observing Time Available for information regarding current ongoing large scale projects in the upcoming semester. The SMA is again offering as a shared-risk capability our expanded processed bandwidth. We have fully vetted our 50% bandwdith increase, to 12 GHz per sideband per polarization, equal to 48 GHz of total processed receiver bandwidth (24 GHz from each of two orthogonally polarized receivers), which we now offer as a standard capability. Please see the Array Status and Technical Information for more details. The full polarization mode, recently under shared-risk mode, has been upgraded to a standard SMA capability in 2021A.

As of the 2011B observing semester, the CfA and the ASIAA use the same time allocation committee (TAC). PIs from ASIAA should submit through the ASIAA queue to take advantage of the guaranteed time share of the ASIAA. Astronomers proposing for IfA time should submit proposals directly to the IfA, following their independent procedures. Proposals from outside institutions should be submitted to the CfA/SAO queue. Collaboration between the partner institutions as well as between the partners and other institutions is encouraged.

Several nights of Director's discretionary time are reserved for potential targets of opportunity and other use. Please contact the TAC chair, Mark Gurwell, and the director, Ray Blundell at SMA_DDT [at] cfa [dot] harvard [dot] edu to apply for this time.

Support for New Users

The SMA staff offers support for observers who are not familiar with the SMA. We can provide support at different levels, from help getting started to full collaboration. Please contact us at sma [hyphen] propose [at] cfa [dot] harvard [dot] edu for questions on proposal preparation, observing techniques and strategies, observing control scripts, and data analysis. Starting this semester, the SMA also offers a first step data reduction of an observation upon request, for PIs who are not familiar with interferometry and/or the SMA.

Number of Nights Available

On average, between five and six nights per week are allocated for routine science observations. Weather statistics suggest that approximately half of the useable time is suitable for observations in the 230 GHz and the 345 GHz bands each. Taking account of time devoted to testing, overhead, and lost to bad weather, the combined CfA+ASIAA share of the SMA time per semester averages about 40 nights each for the 230 GHz and the 345 GHz bands. The TAC uses these averages to set the approximate number of A-rated tracks.

In 2021A, the fraction of time available may be somewhat reduced, depending on safety protocols in place as a response to the coronavirus pandemic. However, we hope to run as close to a normal semester as possible under these constraints.

The oversubscription rate is a function of target RA. The Figure below shows the distribution of target RA proposed in the past few semesters with notable peaks in the inner Galactic Plane.

Proposal Preparation

Existing SMA data

Proposers should query the SMA archive before planning observations to see if existing SMA data suit their scientific goals. Data from past SMA observations are archived by the CfA Radio Telescope Data Center and may be searched. SMA data are publicly available after a proprietary period of 15 months.

RA range and UV coverage

SMA observations are generally executed at night when the atmospheric phase noise is low and often continued into the early morning. Conditions are rarely suitable for afternoon observations. For 2021 May - 2021 November observing, long tracks will be feasible during at least half the semester for sources in the range of roughly RA=17h to 4h. Sources outside this RA range will also be considered if adequate justification is provided. However, since the array configuration schedule is set to accommodate the most highly rangked approved proposals, such observations might not be possible.

The SMA operates in 4 configurations with maximum baselines of 30m (the six antennas on the inner ring of "subcompact"), 70m ("compact"), 220m ("extended"), and 508m ("very extended"). The configuration schedule is determined after the TAC process to best fit the highest ranked approved projects.

Many projects do not need full tracks for adequate uv coverage and/or sensitivity, and the TAC strongly encourages requests for snapshots, partial tracks, and tracks sharing several targets in a field to enhance efficiency.

Technical Information and Tools

For Semester 2021A we are offering as a standard capability our expanded processed bandwidth of 12 GHz per sideband per polarization, equal to 48 GHz of total processed dual reciever bandwidth, all at 140 kHz resolution. All receivers and IF chains offer full bandwidth (4-16 GHz IF range), allowing each receiver to covering 12 GHz in each sideband. In much of the SMA tuning range (~200 - 275 GHz and ~328 - 365 GHz), where receivers with orthogonal polarization have overlapping coverage, the receivers can be tuned with the same LO frequency, providing dual polarization observations for increased line sensitivity. The correlator in this case will also allow full polarization observations near 1.3mm and 870 micron. The receivers are also independently tunable. Around the regions of tuning overlap for the dual recievers, a continuous 44 GHz coverage is possible (with 4 GHz of 'overlap'). See Array Status and Technical Information for more details, where up-to-date technical information about the SMA, including antenna configurations, correlator setups, receiver status, and new or updated SMA capabilities is always available.

The SMA maintains several online tools for planning SMA observations, available on the Tools page.

The Beam Calculator / Sensitivity Estimator is a particularly useful tool to estimate angular resolution, UV coverage and nominal sensitivities for different configurations and weather conditions (precipitable water vapor). Variations in weather may considerably impact actual sensitivities.

Generally, observations at lower frequencies can be done in atmospheric conditions of higher precipitable water vapor. Standard values are < 4.0 and < 2.5mm of water vapor for observations in the frequency ranges <300 and 300-420 GHz, respectively. Proposers must indicate and justify the atmospheric conditions required for their scientific goals. The SMA is more oversubscribed in the weather conditions suitable for the 350 GHz band (< 2.5mm water vapor).

The Passband Visualizer Tool provides interactive information on spectral line coverage and tuning.

SMA observations require calibrator sources for bandpass, gain, and flux calibration. Quasars are generally used for bandpass and gain calibration; however, suitable calibrators may not be available for all parts of the sky particularly at the higher frequencies. See The Submillimeter Calibrator List. Solar system bodies are generally used for flux calibration but may not be available at all times of the year. Observers should show that their proposed observations can be adequately calibrated.

Proposals should provide clear justifications for the rms flux sensitivities, spectral resolutions, antenna configuration(s), weather conditions, and calibration strategies needed to achieve their science goals.

Proposal Forms and Proposal Submission

Proposals are submitted through each individual PI's SMA Project Account. The project account contains all information about an observer's proposals and projects, and will persist for reuse in future proposal cycles. All SMA project activities begin at the user's My Projects page. Project accounts may be created from the login page if necessary (current SMAOC account holders do not need a separate project account).

Using the proposal submission facility, drafts may be created and edited at any time, but may only be submitted within a few weeks prior to the proposal deadline. Each proposal consists of an on-line cover form and technical information forms, and an attached scientific justification in PDF format. Proposals may be saved and edited on-line as often as needed prior to final submission.

The scientific justification is limited to a maximum of four US-letter sized pages including all text (11pt or larger, with reasonble margins) figures, tables and references. The PI is now free to design their proposal within those boundaries, such as mixing figures within text. The PI should aim for approximately equal space for prose (science justification+technical rationale) vs figures, tables, etc., and text alone should not exceed 3 pages. PLEASE NOTE: typically, a picture is truly worth many words, and proposals that are primarily text will generally not fare well. We strongly urge the PI to consider readability by TAC members; they are experts, but may not be experts in your field.

Proposal Evaluation

Proposal selection is based on clearly demonstrated scientific merit and technical feasibility.

The TAC assigns each proposal a numerical score and recommends an amount of time to be allocated. The proposals are ranked and grouped into three categories: A (best effort to execute), B (may be executed as conditions permit), and C (will not be executed). Proposers are notified of their proposal rating by e-mail shortly after the TAC completes its work, typically within about 7-8 weeks of the proposal deadline. Please see the TAC Procedures for more details of the TAC review process.

Accepted Proposals and SMA Observing

All accepted proposals are shared-risk, with no guarantee of success. Standard proposals accepted but not observed due to time constraints will generally not be carried over and must be resubmitted in response to a future call for proposals.

Usually, principal investigators of successful proposals should be prepared to provide an observer on Mauna Kea. Most proposals are queue scheduled to maximize return based on the prevailing weather conditions and instrument status. The SMA scheduler decides which project will be observed each night. It is unlikely that visiting observers will execute their own project when present on Mauna Kea. Due to the ongoing pandemic, we are currently not hosting any visitors, including SMA staff not stationed in Hawaii, and it is uncertain when this will change. Therefore, at this time we do not know if observing support by PIs will be required for successful 2021A proposers.


Data from SMA observations may be retrieved from the CfA's Radio Telescope Data Center archive for reduction. Due to the larger bandwidth and finer resolution of the new correlator, the data sizes are significantly larger. Raw data from a typical 12 GHz BW dual receiver track will take up to 100 GB on disk and a full polarization track will require twice that. A software tool, SMARechunker, can be used to rebin the data - a factor of 8 rebinning (to 1.117 MHz resolution) should be adequate for many spectral line observations. The data can also be retrieved at a lower spectral resolution from the archive if desired. These sizes are for 30s scan times and 12 hr tracks and will be larger if smaller scan sizes are used for finer visibility sampling, e.g., in the very extended configuration. Please see the Radio Telescope Data Center webpages for more details on data processing and hardware requirements.


Please e-mail any questions about preparing and submitting proposals to sma [hyphen] propose [at] cfa [dot] harvard [dot] edu.

Last updated: 2021-Jan-30 by Mark Gurwell