With the development of the space shuttle, manned spacecraft and aviation satellite technology, human space activities have entered a new era. Today, the way of humanity entering the space is no longer simply launching the spacecraft into space for a single task, but also towards a system-level network development. The Big Dipper Program of China and several Constellation program of Europe have confirmed the trend. Rapid globalization of information services also have to rely on space-earth integrated networks. To investigate space more accurately and comprehensively, to make more use of space, to accelerate the development of the information age, the space-earth integrated networks has become an inevitable trend of information technology development.
The future network integration is the integration of satellite networks, the Internet, wireless mobile networks, marine network and other network, since each network uses a different standard, based on different forms of physical resources, working in different frequency bands, and therefore they have differences in power, coverage, transmission capacity, and control overhead, etc. Building an integrated network requires every single network infrastructure with capability of effective organization and collaboration on the integration of a wide coverage network, which provides effective network "access at any cases" , i.e., it works at any place at any time for users. The space-earth integrated networks provide such a possibility.
The space-earth integrated networks have three main characteristics: First, seamless global coverage: it requires the implementation of the full day seamless communication, navigation, observation and monitoring coverage. Also, it involves space and various regions of the world, covering a wide region; Second, flexibility: which has the capability of dynamic networking for emergencies; the third is a strong synergy of information, which can be used for different applications and services for a variety of information resources management, coordination and optimization, aiming to maximize the development and utilization of each kinds of information resources.
The space-earth integrated networks have widespread application fields, such as earth observation, deep space exploration, modern air traffic management, network-centric warfare, civilian communications, etc. Currently, research in this area and constructions have been started, and the United States and other developed European countries as well as some companies are carrying out some related systems, some of which have been put into practical use.