The Submillimeter Array (SMA) consists of eight diameter radio telescopes arranged as an interferometer for submillimeter wavelength observations. It is the first purpose-built submillimeter interferometer, constructed after successful interferometry experiments using the pre-existing James Clerk Maxwell Telescope and Caltech Submillimeter Observatory (now decommissioned) as an interferometer. All three of these observatories are located at Mauna Kea Observatory on Mauna Kea, Hawaii, and have been operated together as a ten element interferometer in the 230 and 345 GHz bands (eSMA, for extended Submillimeter Array). The baseline lengths presently in use range from . The radio frequencies accessible to this telescope range from which includes rotational transitions of dozens of molecular species as well as continuum emission from interstellar dust grains. Although the array is capable of operating both day and night, most of the observations take place at nighttime when the atmospheric phase stability is best. The SMA is jointly operated by the Smithsonian Astrophysical Observatory (SAO) and the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA). History The SMA project was begun in 1983 as part of a broad initiative by Irwin Shapiro, the new director of the SAO, to produce high resolution astronomical instruments across the electromagnetic spectrum. Initially the design called for an array consisting of six antennas, but in 1996 ASIAA joined the project and funded the construction of two additional antennas and the expansion of the correlator to accommodate the near doubling of the number of interferometer baselines. Sites considered for the array included Mount Graham in Arizona, a location near the South Pole, and the Atacama desert in Chile, but Mauna Kea was ultimately chosen due to its existing infrastructure, the availability of a fairly flat area for array construction, and the potential to include the JCMT and CSO in the array. A receiver laboratory was established at the SAO's Cambridge location in 1987. The antennas were constructed at Haystack Observatory in Westford, Massachusetts, partially disassembled and trucked across the United States, then shipped by sea to Hawaii. The antennas were reassembled in a large hangar at the Mauna Kea summit site. The SMA was dedicated and began official operations on November 22, 2003. Array Design The SMA was built just northwest of the saddle between the cinder cones Pu'u Poli'ahu and Pu'u Hauoki, about 140 meters below the summit of Mauna Kea. A perennial issue for radio interferometers, especially those with a small number