Phase Closure at 691 GHz using the Sub-Millimeter Array

Phase closure at 682 GHz and 691 GHz was recently achieved using 3 antennas of the Sub-Millimeter Array (SMA) on Mauna Kea in Hawaii. Initially, phase closure was demonstrated at 682 GHz on Sept. 19, 2002 using an artificial ``beacon" signal. Subsequently, astronomical detections of both Saturn and Uranus were made at the frequency of the CO(6-5) transition (691.473 GHz) on all three baselines on Sept 22, 2002. Phase closure was achieved on Uranus, while Saturn was known to be resolved even on these short baselines (25.19m, 25.23m and 16.44m). The CO(6-5) line was also detected towards Orion BN/KL and other galactic sources. This is the first successful experiment to obtain phase closure in this frequency band. We present these historic detections, as well as images and recent results of ongoing work at this frequency. The Sub-Millimeter Array (SMA) is a collaborative project of the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy & Astrophysics of Taiwan.