The GOES time code service, 1974-2004: a retrospective

Journal of Research of the National Institute of Standards and Technology, March-April, 2005 by Michael A. Lombardi, D. Wayne Hanson

GOESTRAK was originally used in the same fashion as GTDS. Orbital elements were entered into the software, and an ephemeris file was generated and uploaded to the TCGs at Wallops Island via a telephone connection. This procedure resulted in some occasional problems with data errors due to telephone line noise. In October 1999 a computer running a modified version of GOESTRAK was installed at Wallops Island. This computer was interfaced directly to the TCGs, and controlled from Boulder. This method proved to be extremely reliable during the final five years of the service.

11. GOES Applications

GOES time code receivers were once widely found and heavily relied upon at airports, electric power companies, scientific laboratories, observatories, and military installations. The NASDAQ stock exchange once relied on GOES as their master clock for stock market transactions, and the Smithsonian National Air and Space Museum in Washington, DC once had a small exhibit featuring a GOES time code receiver. When the Internet age began, GOES receivers became a source for Internet time synchronization [43], with software drivers written that allowed them to be used as reference clocks for Network Time Protocol (NTP) servers.

The largest users of the time code were probably the Federal Aviation Administration (FAA) and the electric power industry in both the United States and Canada. The FAA operates a system called Mode S, a secondary surveillance radar system that it uses to determine the position of aircraft moving in the airspace over the United States [44]. This system used GOES clocks for time stamping and sensor synchronization. Two GOES receivers, one for the east satellite and one for the west, were located at 147 United States airports, a total of 294 receivers. Additional receivers operated by the FAA brought the total number to well over 400. These units were replaced with GPS receivers in 2002 and 2003. The electric power industry once used thousands of GOES receivers to meet their synchronization requirements along the power grid, which was necessary to transfer power to the areas where it was needed most, and to quickly locate faults. However, the necessary level of synchronization for some applications began to approach 1 [micro]s during the 1990s, a requirement that GPS could meet, but GOES could not [45].

The GOES effort also indirectly benefited other NIST time and frequency services. The technology developed for the GOES TCGs was later used in the original Automated Computer Time Service (ACTS) designed by NIST to synchronize computer clocks [46]. Perhaps more importantly, the experience gained by developing GOES time code receivers [35-37] no doubt played a role in the development of the first GPS common-view timing receiver in 1981 [47], which is still used today by NIST and other national laboratories for international time comparisons.

12. GOES Operations and NBS/NIST Cooperation With NOAA

After its initial development, the GOES time code service was efficiently operated, with minimal cost to NBS/NIST. In the latter years of the service, the oscillator(s) and GPS receiver(s) used as timing references were owned and maintained by NOAA. Six TCGs were built by NBS in the 1970s, and they proved to be exceptionally reliable, with three units still functioning at the end of 2004. The TCGs were controlled by the NIST staff from Boulder, requiring less than two hours of labor per week on average. NOAA personnel at the CDA were extremely helpful throughout the entire GOES time code era, replacing parts and helping solve problems whenever necessary. As a result, only three visits to the CDA were made by the NIST staff during the last nine years of the service (1996-2004).