A clandestine satellite launched on top of a Long March 4B rocket Monday to collect intelligence for the Chinese government.

A Long March 4B rocket lifts off Monday from Taiyuan, China. Credit: Xinhua
 
The Yaogan 21 satellite lifted off at 0322 GMT Monday (11:22 p.m. EDT Sunday) from the Taiyuan space center in northern China's Shanxi province, according to the state-run Xinhua news agency. Liftoff was at 11:22 a.m. Beijing time.

The Long March 4B launcher also carried a secondary payload named Tiantuo 2 designed and built by the National University of Defense, Xinhua reported.

Monday's liftoff marked the fourth space launch by China in a month after a lull in launches in the first half of the year.

China launched a trio of naval surveillance satellites Aug. 9 on a Long March 4C rocket. A Long March 4B booster sent the Gaofen 2 civilian Earth observation satellite to orbit Aug. 19, and a Long March 2D rocket placed two satellites in space Sept. 4.

Monday's flight was not officially announced ahead of time, as is customary with most Chinese rocket launches.

"Yaogan 21 will be used for scientific experiments, natural resource survey, estimation of crop yield and disaster relief," Xinhua reported.

But experts say the Yaogan series of satellites likely serve Chinese military authorities with information from optical and radar imaging sensors.

Tracking data from the U.S. Air Force's space surveillance network indicate the Yaogan 21 payload launched Monday was put in orbit about 480 kilometers, or 300 miles, above Earth. The orbit is tilted 97.4 degrees to the equator.

Two previous Long March 4B rocket launches from the Taiyuan space base in 2008 and 2011 put up Yaogan satellites in similar orbits.

Xinhua reported the 147-pound Tiantuo 2 satellite carries four video cameras capable of tracking and recording moving targets and sending the data back to the ground in real time.

Citing a statement by the National University of Defense, Xinhua said the craft will test the technologies to prepare for the development of more advanced video imaging satellites.

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