The Green Bank Telescope

Following two months of very successful commissioning and the first science observations on the GBT (see the following articles), operation was suspended in early April, one month earlier than planned, to work on the azimuth track. As described in previous NRAO Newsletters, the azimuth track wear strips, on which the azimuth wheels roll, were shifting slightly in a circumferential direction as the wheels rolled over them. After repeated use, the bolts that hold down the wear strips to the track base plate were breaking. Following the recommendation of a consulting engineer, the retention system of one wear strip was modified by increasing the diameter of the retention bolts to 1.5 inches, and nearly tripling the number of bolts in the segment. Tests showed that the motion of the wear strip as the wheels rolled over it was greatly reduced. The contractor, Lockheed Martin, then began a program to modify all 48 wear strip segments in the track. This work was completed on June 8, nearly three weeks ahead of schedule. Realignment of some of the azimuth wheels will follow the wear strip modification.