The Antarctic Submillimeter Telescope and Remote Observatory (AST/RO) is a 1.7 m diameter single-dish instrument, which is fully operational at Amundsen-Scott South Pole Station in several Terahertz, submillimeter-wave, and millimeter-wave bands. AST/RO is one of only two Terahertz observatories in the world, and has two Terahertz instruments, the Terahertz Receiver with NbN HEB Device (TREND) and the South Pole Imaging Fabry-Perot Interferometer (SPIFI), currently operational on the telescope. AST/RO has recently completed two key observatory projects which demonstrate its unique capabilities for mapping the dominant cooling lines of molecular material in the Milky Way. AST/RO has observed these lines with arcminute resolution over regions of sky which are several degrees in size. Radiative transfer models based on these measurements can determine the internal thermodynamic properties of molecular clouds, providing insights about the star formation process and the dynamics of cloud formation and destruction in the Galactic environment. For example, the Galactic Center key project data show that the smooth ring of molecular material 150 parsecs from the Galactic Center is on the verge of coagulating into a single, massive molecular cloud like the one surrounding Sgr B2, and will undergo a burst of star formation. The AST/RO project has observed, reduced, published and publicly released on the Internet a large fraction of all spectral line observations in the frequency octave from 450 to 900 GHz. The proven capabilities of AST/RO will provide critical collaborative observations for the newly-launched Spitzer Space Telescope (SST, see www.spitzer.caltech.edu).
