Call for SMA Science Observing Proposals

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 2017 Nov 16 - 2018 May 15. Proposals must be submitted by:

Wednesday, 6 September 2017, 10:00 HST (Hawaii)
Wednesday, 6 September 2017, 16:00 EDT (Cambridge, MA)
Wednesday, 6 September 2017, 20:00 GMT
Thursday, 7 September 2017, 04:00 CST (Taipei)

SMA Observing Time

The SMA is a joint project funded by the Smithsonian Astrophysical Observatory (SAO) 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.

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, T. K. Sridharan, 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 the new SMA correlator.

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.

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 2017 November - 2018 May observing, long tracks will be feasible during at least half the semester for sources in the range of roughly RA=4h to 16h. 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 approved proposals, such observations might not be possible.

The SMA operates in 4 configurations with maximum baselines of 30m ("subcompact"), 70m ("compact"), 220m ("extended"), and 500m ("very extended"). The configuration schedule is determined after the TAC process to best fit the approved projects.

Many projects do not need full tracks for adequate uv coverage and/or sensitivity, and the TAC strongly encourages requests for snapshots and partial tracks.

Technical Information and Tools

The new SWARM correlator is now fully commissioned, with all four quadrants operating at full speed, spanning an 8 GHz IF range (4-12 GHz ) for each of two receivers at a fixed 140 kHz resolution, without any coverage gaps. All receivers and IF chains offer full bandwidth (4-12 GHz IF range), allowing a dual receiver mode covering 2 X 8GHz, which delivers the widest frequency coverage and the best continuum sensitivity. The receivers allow full polarization observations. They are also independently tunable and can be tuned to cover contiguous 8 GHz-wide bands, providing 16 GHz coverage in each sideband. Around the regions of tuning overlap for the dual recievers, a continuous 32 GHz coverage is possible. 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 two US-letter sized pages of text (11pt or larger) plus two US-letter sized pages of figures, tables and references.

Proposal Evaluation

Proposal selection is based on 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 ten 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. Proposals accepted but not observed due to time constraints will not be carried over and must be resubmitted in response to a future call for proposals.

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.


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. Data from a typical 8 GHz dual receiver track will take up 59 GB on the disk and a full polarization track will require 118 GB. SMARechunker can be used to rebin the data - a factor of 8 lower resolution should be adequate for most spectral line observations. The data can also be retrieved at a lower spectral resolution from the archive if desired. The RAM requirements after this smoothing would be 39 GB and 74 GB to fully load the data into memory and process, as the case with the MIR data reduction package. 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. If the full resolution is retained, the RAM requirements would be 299 GB and 587 GB.


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

Last updated: 2017-Aug-09 by T. K. Sridharan