A computer-generated illustration of the 'Zhang Heng' electromagnetic test satellite in space. Photo: CNR
A computer-generated illustration of the 'Zhang Heng' electromagnetic test satellite in space. Photo: CNR

China this month put into orbit its first seismo-electromagnetic satellite to observe earthquake precursors, paving the way for a ground-space earthquake monitoring and forecasting system.

A Long March-2D rocket projected a 730-kilogram satellite christened Zhang Heng, after the Eastern Han Dynasty polymath who devised the world’s first “seismoscope” 1,886 years ago, into a sun-synchronous orbit at an altitude of about 500 kilometers from the Jiuquan Satellite Launch Center in the northwestern province of Gansu.

China launched its first seismo-electromagnetic satellite, the Zhang Heng, into a sun-synchronous orbit this month. Photo: Xinhua

The China National Space Administration (CNSA) said the cube-shaped satellite would help scientists monitor electromagnetic fields, ionospheric plasma and high-energy particles during its five years of service in orbit. It will record electromagnetic data associated with earthquakes above 6 magnitude in China, particularly in areas that straddle known seismic belts, in a bid to  gather data from on high to build models of the Earth’s geomagnetic field and ionosphere and identify patterns in the electromagnetic disturbances in the near-Earth environment.

The novel satellite, hailed as the pinnacle of China’s sensoring and seismic research, incorporates a high-precision search-coil magnetometer and electric-field probes to measure components and intensity of the Earth’s magnetic and electric fields. It also features a Langmuir probe, a plasma analyzer and a tri-band beacon to measure in-situ plasma and ionospheric profiles.

The satellite, the first of its series, was developed by the China Earthquake Administration and produced by a subsidiary of the China Academy of Space Technology.

China’s western and northern provinces are prone to high-magnitude quakes that have shallow epicenters.

Though predicting earthquakes is never an exact science, breakthroughs in monitoring precursors especially seismo-electromagnetic anomalies in the near-Earth environment, have shown a promising path toward finding out if there is any harbinger of a destructive quake and how to “read” it.

Research shows that just before an earthquake, tectonic forces acting on the Earth’s crust emit electromagnetic waves and twist magnetic-field lines.

An image of the Earth taken from the main body of the Zhang Heng. Photo: China Central Television

The Zhang Heng will help scientists better understand the coupling mechanisms of the upper atmosphere, ionosphere and magnetosphere and the temporal variations of the geomagnetic field, and thus accumulate data for the research of seismic precursors, Xinhua reported, citing the program’s lead scientist, Zhou Feng.

The report said the satellite would not be able to predict earthquakes any time soon, “but it will help prepare the research and technologies for a ground-space earthquake monitoring and forecasting system in the future.”

To detect the subtle ionospheric changes caused by earthquakes and accumulate data on high-energy particles, plasma and electromagnetic fields, sensors on the Zhang Heng must be extremely clean – free of its own disturbances in terms of magnetic fields and charging effects.

Painstaking efforts were also made to ensure observation and sensoring won’t be affected by the “electromagnetic noise” of data transmission.

Six hinged booms nearly 5 meters in length with detectors and probes on the far ends were mounted to decrease interference from the satellite itself. These booms must remain still, and their far ends must not dip more than 2 millimeters in temperature changes of more than 200 degrees Celsius.

“The probes are like wood blocks floating on water. They help us feel the waves from their movements. But they are extremely sensitive, able to detect a change as tiny as a drop of water in a wave as high as the Himalayas,” said Yuan Shigeng, chief designer of the Zhang Heng.