Observations in the 1.3 and 1.5 THz Atmospheric Windows with the Receiver Lab Telescope

The Receiver Lab Telescope (RLT) is a ground-based terahertz telescope; it is currently the only instrument producing astronomical data between 1 and 2 THz. The capabilities of the RLT have been expanding since observations began in late 2002. Initial observations were limited to the 850 GHz and 1.03 THz windows due to the availability of solid state local oscillators. In the last year we have begun observations with new local oscillators for the 1.3 and 1.5 THz atmospheric windows. These oscillators provide access to the 11-10 and 13-12 lines of CO at 1.267 and 1.497 THz, as well as the [N II] line at 1.461 THz. We report on our first measurements of these high CO transitions, which represent the highest-frequency detections ever made from the ground. We also present initial observations of [N II] and discuss the implications of this non-detection for the standard estimates of the strength of this line.