Chinese Dual Ziyuan-2 Sats Watch Earth In Tandem

DRAGON SPACE

XSCC mission controllers celebrate the successful launch of ZY-2B. (Photo: Xinhua News Agency)

by Cheng Ho
Tokyo - Nov 22, 2002
The newly launched Chinese Ziyuan-2B (ZY-2B, "Ziyuan" means resource) remote sensing satellite had reached its operational orbit and would join its predecessor to make terrestrial observations in tandem, Xinhua News Agency reported on Nov. 15.

A Changzheng-4B (Long March-4B) rocket delivered ZY-2B into space with a liftoff from the Taiyuan Satellite Launching Center (TSLC) in the northern Shanxi Province at 11:17 a.m. Beijing Time (0317 UTC) on Oct. 27.

An unusual incident occurred soon after launch when some of the debris from the CZ-4B staging had drifted off-course from landing in the designated debris impact zone. At least 19 pieces of debris ended up in a nearby village.

Unfortunately a piece of debris had injured the left foot of a boy.

People's Liberation Army (PLA) Daily reported on Nov. 8 that under the careful control and monitoring of the mission operators at the Xi'an Satellite Control Centre (XSCC) in the central Shaanxi Province, ZY-2B had successfully deployed its solar arrays soon after reaching its initial orbit.

In the two weeks after the launch, mission controllers had carried out attitude adjustments and three orbital maneuvers.

Xinhua reported that ZY-2B reached its present operational orbit on Nov. 12 at 10:53 p.m. Beijing Time (1453 UTC).

ZY-2B is in a sun-synchronous polar orbit of 477.5 x 505.4 km, with an inclination of 97.4 degrees and a period of 94.4 minutes.

The State news agency said that ZY-2B would operate in tandem with its sister craft ZY-2A, which was launched in September 2000.

ZY-2A, which is operating beyond its designed lifetime of two years, is in a different but more circular sun-synchronous polar orbit of 490.0 x 492. 8 km; with an inclination of 97.3 degrees. ZY-2A orbits the Earth once every 94.4 minutes.

PLA Daily reported that ZY-2B had returned several "high quality" test images in the first two weeks.

The weekly Chinese language aerospace publication China Space News reported on Oct. 30 that the Chinese Academy of Space Technology (CAST), which designed and built both ZY-2 satellites, had made improvements in "certain technical designs". This resulted in higher image quality from ZY-2B than its sibling craft.

Although the image resolution of both ZY-2 satellites has never been released, it is believed to be higher than that of ZY-1A -- the joint China-Brazil Earth Resources Satellite-1 (CBERS-1). The highest image resolution of ZY-1A is 20 meters.

Mission controllers said that the operation of ZY-2B was nominal.

To maximize the operational efficiency of both ZY-2 satellites, XSCC designed and implemented a "dual satellite observation and control network". This would ensure the precise operation area of each satellite and allow tandem observations of the Earth.

During the deployment of the dual satellite observation and control network, XSCC tested its satellite communications network as well as new technologies such as observation and control software common platform, and spacecraft control language.

The test further verified and raised the overall capability of tightly integrating monitoring and control of spacecraft and launcher.

XSCC also employed a transparent centralized control model to improve the distribution and utilization of control resources. This helped resolve the conflict of cross-operation of satellite management and its realtime monitoring and control.

Mission controllers at XSCC said that after further on-orbit testing of ZY-2B, the EO satellite would be handed over to satellite application department in the near future.

DRAGON SPACE

New Chinese EO Sat Will Keep Tabs On Terrestrial Happenings

Tokyo - Oct 30, 2002
China successfully placed a new Earth observing satellite into orbit on Sunday (Oct. 27). With the launch of Ziyuan-2B (ZY-2B, "Ziyuan" means resource), China now has three Ziyuan remote sensing satellites to monitor changing conditions of the Earth's surface. A 45-meter tall Changzheng-4B (Long March-4B) rocket, with a liftoff mass of 250 tonnes, blasted off from the Taiyuan Satellite Launching Center (TSLC) in the northern Shanxi Province at 11:17 a.m. Beijing Time (0317 UTC), Xinhua News Agency reported.

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