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.
The SMA Time Allocation Committee warmly welcomes submission of
proposals for the upcoming 2021B 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
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. 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.
Accepted Proposals and SMA In-Person Observing
The joint SAO-ASIAA SMA Time Allocation Committee (TAC) solicits
proposals for observations for the period
2021 Nov 16 - 2022 May 15. Proposals must be
Thursday, 16 September 2021, 10:00 HST (Hawaii)
Thursday, 16 September 2021, 16:00 EDT (Cambridge, MA)
Thursday, 16 September 2021, 20:00 GMT
Friday, 17 September 2021, 04:00 CST (Taipei)
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). The SMA 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.
Standard Observing Proposals: Beginning with 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.
Large Scale Science and Key Projects: In addition to
standard proposal programs, SMA from time to time offers the
opportunity for large-scale projects needing observing time in the range of
100 to 1000 hours. As a result, if one or more large scale project
proposals is successful, the time available for standard projects will
be reduced. Proposers should refer
Time Available for information regarding ongoing large
scale projects in the upcoming semester.
DDT Proposals: 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.
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, reconfigurations, and bad weather, the combined
CfA+ASIAA share of the SMA time per semester averages about 50 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 2021B, the fraction of time available may be reduced,
depending on safety protocols in place as a response to the
coronavirus pandemic, and considering a backlog of repairs and
maintenance that needs to be performed. However, we hope to run as
close to a normal semester as possible under these
The oversubscription rate is a function of target RA and DEC. The
figure below shows the distribution of target RA proposed in the past,
with notable peaks along the inner Galactic Plane, nearby star-forming
regions, and extragalactic fields.
For some basic information on the SMA and its capabilities, as well
as more general background information, please see
the Technical Information, Tools, and Resources
section below. There you will find links to the basic specifications,
technical information, useful tools, and several presentations on the
SMA and interferometry in general.
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. 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.
Under nominal conditions, 8 antennas are available for scientific
observations with the SMA. However, maintenance and operational issues
may reduce the number of active antennas available for any given
track. In order for a track to be considered passing, the project must
a) meet the weather stringency requirements for the track, and b) have
a minimum number of elements available in the array, the latter of
which is defined as follows:
- Full-polarization tracks: 7 working antennas with both an
operational LCP and RCP receiver
- Dual-polarization tracks: 14 working receivers (7 tuned to the RxA
tuning, 7 tuned to the RxB tuning)
When the array meets the above, the full observing time is charged
to the project (i.e., the track is considered "passed"), provided no
other significant technical or weather issues. When there are fewer
than the above number of elements, but the weather requirements for
the project are met, then the project is charged for time/tracks in
the following fashion:
- 6 working antennas/12 working receivers: If the weather is better
than requested (e.g., < 2.5 mm PWV during observations, when < 4 mm
PWV was requested), then a full track is charged. Otherwise, the
project is only charged half-time. I.e., 2 tracks w/ at least 6
antennas/12 receivers are combined to make a single "passing"
- 5 working antennas/10 working receivers: The project is only
charged a third of the time. I.e., 3 tracks w/ at least 5 antennas/10
receivers are combined to make a single "passing" track.
- Fewer than 5 working antennas/10 working receivers: No time
There are two important caveats about the above. First, it does not
apply to triggered ToO observations, where the array is accepted
"as-is" at the time of trigger. Second, the above does not account for
differences in the synthesized beam that may arise from a limited
number of elements in the array, and thus may not be suitable for
high-SNR projects, where imaging fidelity is primarily limited
uv-coverage. PIs with projects that fall into this category may
stipulate as much in the "additional instructions" field in the
individual time requests, in which case the project will nominally not
be run with fewer than 7 antennas.
The SMA has been in operation for nearly 20 years, and has an
extensive science data archive. Proposers should query the SMA archive
prior to planning new 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.
If older data exist, the PI should include a short statement in
their proposal discussing why new observations are warranted.
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
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
reasonable 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.
Proposals should provide clear statements on, and justifications
for, the rms flux sensitivities, spectral resolutions, antenna
configuration(s), weather conditions, calibration strategies, and (if
applicable) any time constraints needed to achieve their science
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 November
- 2022 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 most highly ranked
approved proposals, such observations may 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");
see Technical Information, Tools, and Resources
section below for more infomation. The configuration schedule is
determined after the TAC process to best fit the highest ranked
Many projects do not need full tracks (a full rise to set
observation)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.
For Semester 2021B 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. In the case of equal LOs for the two selected receivers,
it is also possible to obtain 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 are always available.
The SMA maintains several online tools for planning SMA observations,
available on the Tools page.
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
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).
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.
Status and Technical Information
and Proposal Information (2021A) PDF of 19 Feb 2021 presentation
Proposal Planning Tools
Presentations from the 2021 SMA Interferometry School
Proposal selection is based on clearly demonstrated scientific
merit, alignment with SMA uniqueness and capabilities, 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 7-8 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.
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 2021B
Please e-mail any questions about preparing and submitting proposals to
sma [hyphen] propose [at] cfa [dot] harvard [dot] edu.
Last updated: 2021-Aug-14 by Mark Gurwell