Thirteenth International Symposium on Space Terahertz Technology, Harvard University, March 2002. Prospects for Terahertz Radio Astronomy from Northern Chile R. Blundell, J.W. Barrett, H. Gibson, C. Gottleib, T.R. Hunter, R. Kimberk, S. Leiker, D. Marrone, D. Meledin, S. Paine, D.C. Papa, R.J. Plante, P. Riddle, M.J. Smith, T.K. Sridharan, C.E. Tong, and R.W.Wilson Harvard Smithsonian Center for Astrophysics 60, Garden Street, Cambridge, MA 02138, USA M. Diaz, L. Bronfman, and J. May Universidad de Chile A. Otarola European Southern Observatory S.J.E. Radford National Radio Astronomy Observatory Abstract The teraheitz (THz) frequency range (1-3 THz, or 100-300 pm wavelength) provides an important window on the far-infrared Universe. Recent studies of the transmission spectrum of Earth's atmosphere reveal that windows centered at 1.03 THz, 1.3 THz, and 1.5 THz become significantly transparent from high altitude (> 5000m) sites in northern Chile. We are currently building a small radio telescope antenna in order to assess the feasibility of ground-based THz astronomy. The antenna, an 800 mm diameter paraboloid, has a surface accuracy of 3 1,1M rms and a beam width of about 1 arcminute at 1.5 THz. It will be coupled to HEB receivers, also under development at SAO. Initial astronomical tests will be carried out in the 850 GHz and 1.03 THz atmospheric windows. Receivers for the two higher frequency bands are currently under development and are expected to be deployed towards the end of 2002. Introduction Between the far infrared and the shortest radio wavelengths lies a region of the electromagnetic spectrum rich in astrophysical information, yet virtually unexplored. The dearth of scientific data in this spectral region is not due to lack of interest, for it provides unique targets for both interstellar chemistry and star formation studies. However, even though windows at 225 and 200 11M had been observed from Pikes Peak as long ago as 1971 1 , and it had been predicted that the South Pole may offer some atmospheric transmission in the far infrared 2 , it has been generally accepted that 1 THz represents the upper frequency bound for radio observation from the ground 3 . Hence, this frequency regime has been left to a few groups with access to balloons or aircraft, 159