Because the telescope is small, direct-drive torque motors are used on both axes, with the advantage that the drive system has no gear trains. Although the motors provide only of torque, the telescope can change orientation at 10 degrees per second. Both axes are monitored by 16 bit shaft encoders and tachometers read at 100 Hz by the telescope-control computer to calculate torque corrections for pointing. The pointing of the telescope is fine tuned at the beginning of each season by using a coaligned optical telescope to observe a large number of stars covering a wide range of azimuths and elevations. A least-squares fit to the pointing errors is used to define 5 pointing parameters (offsets of the azimuth and elevation encoders, effective longitude and latitude, and the small nonperpendicularity of the azimuth and elevation axes). Because the relatively large beam of the telescope makes continuum observations of planets inconvenient, pointing is checked weekly by radio continuum observations of the limb of the Sun. Although during the observing season (fall, winter, and spring) the Sun transits below the elevation of most carbon monoxide observations, it is the only practical astronomical source for pointing checks. At elevations used for observations, the root mean square pointing errors of the telescope were less than about 1', about 1/9 beamwidth. Receiver The heterodyne receiver, which uses a superconducting-insulator-superconducting (SIS) Josephson junction as the mixer, is the two-backshort design of Kerr (Pan et al. 1983). A scalar feed couples the microwave signal to the receiver, where it is mixed with a local oscillator (LO) signal to produce a 1.4 GHz intermediate frequency (IF) signal that is further amplified with a low-noise high electron mobility field effect transistor (HEMT FET) amplifier, and passed to the IF section of the receiver. The IF section further amplifies the signal and heterodynes it down to 150 MHz, passing a bandwidth of 200 MHz to the spectrometer. The LO signal is generated by a Gunn diode oscillator whose frequency is controlled via a phase-lock loop system by a computer-controlled frequency synthesizer. The SIS mixer and the FET first stage amplifier are on the liquid helium-cooled cold stage of a vacuum dewar; the rest of the electronics are room temperature. Typical receiver noise temperatures at 115.3 GHz are 65–70 K single sideband (SSB). Although the performance improves somewhat to 55 K SSB if the helium dewar is pumped to 2.7 K,