SMA: The Submillimeter Array

Link to SMA Web site

I. General project/facility description

1. Overview of the facility/project
   The Submillimeter Array (SMA) consists of eight six meter diameter antennas located near the summit of Mauna Kea in "millimeter valley", about 150 meters west of the JCMT at an elevation of 4080 m. The Array is currently equipped with SIS mixer receivers to cover the bands 180-250 GHz, 240-350 GHz, and 620-690 GHz. The IF bandwidth is 2 GHz, and processing of both upper and lower sideband signals is implemented. The correlation spectrometer is very flexible in configuration, and  the full bandwidth mode allows for 1 MHz resolution over 2 GHz in two receiver bands simultaneously. In Hilo, at sea level, there is an 18,000 square foot facility to support the summit operation. SAO owns two bedrooms at the mid-level general support facility.

2. Managing institution and organization
   The SMA is a joint project of the Smithsonian Astrophysical Observatory (SAO) (85 percent), a bureau of the Smithsonian Institution and the Institute of Astronomy and Astrophysics of the Academia Sinica (ASIAA) of Taiwan (15 percent). As described by the Operating agreement between SAO and the University of Hawaii, the Institute of Astronomy (IfA/UH) receives 15 percent of the observing time. The Director of the SMA is an employee of the SAO. The distribution of observing time is thus: SAO, 72 percent, UH, 15 percent, and ASIAA, 13 percent. The operating staff in Hawaii is 26 people, supported by a staff of 31 in Cambridge. There is an external Advisory Committee which meets once per year, and three separate telescope allocation committees.

3. Funding source(s)
   The operating budget is split 85/15 percent between SAO and ASIAA, which are funded through their parent organizations, the Smithsonian Institution and the Academia Sinica. The SAO support is in the form of direct Federal appropriation by Congress to the Smithsonian Institution. The SI budget is considered with the the Department of the Interior and related agencies.

4. Construction history and cost
   The total cost of construction from inception in 1990 to dedication in November 2003 was $103M (actual dollars - approximately equal to 1997 dollars) (of which ASIAA contributed about $15M in kind). This included the design, construction, partial operation of the array before 2004, and support of a science group during the construction period. The construction included $6.2M for the Hilo support facility.

5. Operational history and cost
   Full operation of the SMA began in FY 2004. SAO contributes about $8M/year, which is in the form of support for 34 staff positions, $2.2M for direct operations, $2.0M for instrumentation, and $0.5M for renovation. ASIAA contributes about $1.4M/year. This budget also supports all the scientific staff associated with the project. 

II. Technical details

1. Specifics of telescope/instrument
   

   	Current capability	2007 goal
   Antennas	8 x 6 meter diameter + CSO & JCMT
   Surface accuracy	12-24 µ	12 µ
   Pointing accuracy	3"	1"
   slew rate	4 °/sec
   baselines	8 - 508 m	8 - 1000 m
   IF bandwidth	2 GHz
   Highest spectral res	0.2 MHz
   Fastest sampling	2 sec	1 sec
   Data format	MIR (OVRO)
   Data processing	MIRIAD, AIPS

   1.3 mm band	Current capability	2007 goal
   Frequency coverage	175 - 255 GHz
   Field of view	55"
   max res	0.4"	0.2"
   receiver (DSB)	70-90 K	70 K
   Sensitivity in 6 hrs (cont)	0.8 mJy	0.4 mJy
   Sensitivity in 6 hrs (1 km/s, 1" res)	2.0	1.0

   0.9 mm band	Current capability	2007 goal
   Frequency coverage	250 - 355 GHz
   Field of view	36"
   max res	0.3"	0.15
   receiver (DSB)	80-150 K	80 K
   Sensitivity in 6 hours (cont)	2.0 mJy	1.0 mJy
   Sensitivity in 6 hrs (1 km/s, 1" res)	3.0	1.5

   0.45 mm GHz band	Current capability	2007 goal
   Frequency coverage	600-720 GHz
   Field of view	18"
   max res	0.15"	0.07
   receiver (DSB)	300-600 K	300 K
   Sensitivity in 6 hours (cont)	20 mJy	10 mJy
   Sensitivity in 6 hrs (1 km/s, 1" res)	2.0	1.0

2. New capabilities anticipated/planned in next 5-10 years
   
   • Receivers for the 320 - 420 GHz band. these can be used in the overlap region with the current 250 - 355 GHz receiver to obtain full polarization measurements, or to improve the sensitivity by root two.
   • Receivers for the 800 - 900 GHz band
   • Receivers for the 400 - 500 GHz band
   • Several more pads to increase the baseline coverage to 1 km (note that any development on Mauna Kea must pass a stringent review process).
   • Atmospheric phase delay monitoring techniques.

III. User profile

1. % of "open skies" time
   About 10% of the SAO time is currently available to non-partner institutions. Fraction expected to increase as instrument becomes more user friendly.
2. Institutional affiliations of users
   SAO/CfA, ASIAA, U Hawaii are partners.

3. Student access, involvement, usage
   Graduate students have been involved in the testing, operating, and science programs of the SMA. Some technical development projects have been carried out by students.

IV. Science Overview

1. Current forefront scientific programs
   
   • Monitoring of Sgr A* at 345 GHz in all polarizations
   • Spectroscopic study of the atmospheres of Mars and Titan
   • Imaging of water masers at 321, 325 and 658 GHz
   • Imaging of CO (3-2) in nearby galaxies
   • Imaging of molecules in atmospheres of late type stars
   • Study of SCUBA galaxies

2. Major discoveries (through 1999)
   New facility.

3. Science highlights of last 5 years
   New facility.

4. Main future science questions to be addressed

• Circumstellar environment of galactic center
• Resolve debris disks around solar type stars
• Chemistry of circumstellar envelopes in low and high mass stars
• Formation of  giant molecular clouds in nearby galaxies
• Gas and dust in earliest generation of galaxy formation

1. Synergies with other major forefront facilities
   
   • 10 element interferometry capability with JCMT and CSO under development (double the collecting area at 230 and 345 GHz, increase the maximum baseline by 50 percent, and increase the number of baselines from 28 to 45).
   • Coordinated observations of Sgr A* with Keck, VLT, OVRO, and Chandra.

2. Unique contributions
   

V. Education/Outreach activities

1. Visitor facility
   
   • Participate in support of Mauna Kea Observatories Visitor Center at Hale Puaho
   • Facility tours by prearrangement
   • Contribute two speakers a year to monthly lecture series
   • Advise UH in the development of the Mauna Kea Education Center

2. Student programs
   Smithsonian Predoctoral Fellowship. Available to students from any university who have completed pre-thesis requirements and wish to do their thesis work on the SMA with an SAO advisor. There are currently six students in this program, who are based in Hilo or Cambridge.

3. Other (as apply)
   

VI. Documentation/website URLs

1. URL of facility website
   http://sma-www.harvard.edu"
2. URL of EPO website
   
3. URL(s) of any brief overviews of project/facility
   
4. URL(s) of miscellaneous documentation
   http://sma1.sma.hawaii.edu" (SMA Observer Center - information for users)