overall: 87 in x 24 in x 30 in; 220.98 cm x 60.96 cm x 76.2 cm
master clock system, clock a
master clock and distribution assembly, clock a
United States: California, Mojave Desert
This is timing equipment from NASA's Goldstone Deep Space Communications Complex in the Mojave Desert near Barstow, Calif. It was installed at Goldstone about 1984. Based on specifications from NASA's Goddard Space Flight Center, the assembly was designed and made by TRAK Microwave of Tampa, Florida, and used at Goldstone to provide time codes for the ground station and space navigation until 2006. While in service, the assembly timed an impressive list of missions, including the two Voyagers launched in 1977 and the highly publicized Mars missions in 1996, 2001, 2003 and 2005. The equipment could track about thirty missions simultaneously and served about one hundred users.
The assembly contains three clocks—Clocks A, B and C (2008.0145.01, .02, and .03)—that work together as the master clock. Also known as a triple redundant clock, the three together "vote" on a single time of day, with agreement between two of the three determining the correct time. The master clock receives a reference frequency from a suite of atomic frequency standards (one primary and three backups). The master clock converts that frequency into time codes. Reference frequency signals and time codes are in turn distributed by the time insertion distribution system (2008.0145.04) to user locations in NASA's Deep Space Network for tracking spacecraft and radioastronomy experiments.
Time and frequency are essential to the Deep Space Network, a group of three communications facilities placed approximately 120 degrees apart around the world at Goldstone, near Madrid, Spain and near Canberra, Australia. The network synchronizes the three stations plus the Jet Propulsion Laboratory in Pasadena, CA, to an accuracy of microseconds through comparisons with each other and with time from the Global Positioning System.