China currently has a VLBI (Very Long Baseline Interferometry) network of four radio antennas: Shanghai (25m, all panel, X/S, est. 1987), Urumqi (25m, all panel, X/S, 1994), Kunming (40m, inner 25m panel, X/S, est. 2006), and Beijing (50m, inner 30m panel, X/S, est. 2006). These are linked via internet and optical fiber to a data center in the Shanghai Astronomical Observatory.

VLBI antennas receive extremely faint radio signals from celestial objects as far as several billion light years away. The relative three dimensional positions between antennas thousands of kilometers apart can be measured to an accuracy of a few millimeters by: 1. measuring the time difference (about 0 to .02 seconds, to a precision of 10 billionth of a second) a signal from a celestial object is received by different antennas; 2. multiplying this time delay by the velocity of the radio waves (app. 300,000 km/s); 3. repeating the procedure for three or more celestial objects (over 24 hours, one station can receive information for up to 500 celestial objects). Such systems are extremely important for both astronomical tracking and geodetic studies.

China primarily uses its VLBI network to track its Chang E lunar probe and plans to also use it for the Kuarfu solar activity and space weather program. In addition, China participates in a number of international projects such as SELENE (for measuring lunar gravity) and WSO/UV (World Space Observatory in the UV Band).

VLBI is of limited military and little commercial value. It is not surprising then, that China is willing to actively cooperate in a number of international VLBI research programs. This is in contrast to China’s abandoning the EU Galileo project. Here, commercial interests even trumped military ones. China continued to participate in Galileo even as other countries such as India objected over various national security issues. On the other hand, China pulled out of the Galileo project as soon as it announced plans to develop the Beidou-2 into a commercial GPS system. Looking over China’s different space science programs, it is necessary to compare the various factors influencing their continued cooperation or disengagement.