Product Centers, Combination Centers, and other associated components). The current service components are primarily funded and maintained by their host countries on behalf of the scientific community. Research studies are undertaken by the participating institutions in order to produce the highest-quality products. Directing and Governing Boards of the services have the important role of reviewing the work of the different components of the service, coordinating their actions, and deciding policy. For the ILRS Central Bureau, the director, secretary, science coordinator, and two of the three analysis specialists are from the United States. For the IVS, the network and technology coordinators are from the United States, as are the Correlators and Operation Centers Representative. For the IGS, seven members of the Governing Board are from the United States, and NASA supports the IGS Central Bureau. This demonstrates that the various services are vulnerable to the vagaries of funding and support of the U.S. participants.

In summary, the geodetic infrastructure, which supports myriad national and international interests in the Earth sciences, consists of geodetic networks (ground-based instruments and their attached GNSS/GPS receivers, radio telescopes, laser tracking stations, DORIS beacons, tide gauges, and gravity meters), geodetic platforms (satellites, aircraft, and other vehicles), the geodetic data processing and service centers and, of course, the geodesists themselves. Each component is a critical link in the chain from the raw data to the refined measurements and products (such as the ITRF described in Chapter 5). A failure in any component is a failure in the technique, and all the techniques are required to support the important scientific studies addressing such issues as global climate change and natural hazard understanding, prediction, and mitigation.