The new 150-foot radio telescope of the Air Force Cambridge Research Laboratories Sagamore Hill Radio Astronomy Observatory at Hamilton, Mass., is reported in partial operation. The reflector, which was placed on its supporting towers last September, is capable of motion in the horizontal plane and is now being used to view radio sources as they rise and set. Equipment to control vertical motion and tracking of sources is being installed, and the instrument is expected to be in full operation by the end of the year. Two other radio telescopes of the same size have been placed in operation by Stanford University in Palo Alto, Calif., and by the Naval Research Laboratory at Chesapeake Beach in Maryland.