The United States Air Force Weather operates globally to collect observations of atmospheric conditions. Instruments include human observers, weather satellites, and weather radars. A new era is forthcoming in the domain of weather satellites, as satellite sensors are improved and additional weather satellites are launched by China, Japan, and others. The United States is integrating its civilian and military weather satellites but the Defense Meteorological satellite (DMSP) and national civilian satellites will both continue in use for a decade or more. Sensor improvements in the DMSP will increase the number of optical channels while also increasing sample quantization from 8 to 12 bits. Prior operation emphasized storing imagery and dumping the data from a full orbit at one earth station. A small tactical terminal (STT) has been developed to allow receipt of the satellite real-time downlink at any geographic location. Thus, with a suitably dispersed group of STTs, data can be collected in near real time on a global basis.
Although it may not seem significant, it is highly desirable to retrieve and make use of all satellite data in near real time. An example of the need for timely data is in the case of tropical storms, where timely data can increase warning time in case of a tornado, hurricane or typhoon. Weather touches all lives, but can be of critical importance in military operations. The U.S. Air Force has had an operational requirement for retrieval of global data within 15 minutes.
One best use of the weather satellite data is for initializing the complex computer weather model, which is run several times each day. But due to the magnitude of the data that may be downlinked by a single pass of a weather satellite, transmitting this data back to the Air Force Weather Agency, where it may be used in the model, presents a significant global data commu-nications challenge. This paper describes a Ka Band satellite communications network to accomplish the communications. This is representative of a class of emerging international data communications applications that might be supported by a global Ka Band satellite system. Further, the proliferation of national weather satellites data offers an opportunity to share weather data which might also be accomplished through a global Ka Band satellite communica-tions system. Latency is compared for satellite communications and fiber optic cable relay.
