Call for SMA Science Observing Proposals
SMA Observing Time
Support for New Users
Number of Nights Available
Accepted Proposals and SMA Observing
The joint CfA-ASIAA SMA Time Allocation Committee (TAC) solicits
proposals for observations for the period
2018 May 16 - 2018 Nov 15. Proposals must be
Thursday, 8 March 2018, 11:00 HST (Hawaii)
Thursday, 8 March 2018, 16:00 EST (Cambridge, MA)
Thursday, 8 March 2018, 21:00 GMT
Friday, 9 March 2018, 05:00 CST (Taipei)
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.
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.
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
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
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.
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 2018 May
- 2018 November
observing, long tracks will be feasible during at least half the
semester for sources in the range of roughly RA=16h 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 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
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 selection is based on scientific merit and technical
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.
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
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-Dec-19 by T. K. Sridharan