China launches experimental Shiyan satellite

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A Long March 4B rocket takes off from the Taiyuan space base with a Shiyan 6 satellite. Credit: Xinhua

China launched the third in a series of experimental Shiyan 6 satellites April 8 aboard a Long March 4B rocket, beginning a mission to test new space technologies, including a new super-black coating to absorb stray light and improve the sensitivity of on-board optics.

The Shiyan 6-class satellite lifted off at 2301 GMT (7:01 p.m. EDT) on April 8 from the Taiyuan space center in northern China’s Shanxi province, according to the China Aerospace Science and Technology Corp., the biggest state-owned contractor for the country’s space program.

A 150-foot-tall (45.9-meter) Long March 4B rocket carried the Shiyan 6 spacecraft into orbit from Taiyuan, with its four booster engines generating more than 670,000 pounds of thrust at full power.

After flying south from the launch base, the rocket shed its liquid-fueled first stage about two-and-a-half minutes into the mission, followed by ignition of the Long March 4B’s second stage main engine and separation of the rocket’s payload shroud, which protected the spacecraft during the first few minutes of flight through the atmosphere.

A third stage then ignited to place the Shiyan 6 spacecraft into a polar orbit about 620 miles (1,000 kilometers) above Earth, with an inclination of 99.5 degrees to the equator.

U.S. military tracking data confirmed the mission deployed its payload into an on-target orbit, and Chinese officials declared the launch a total success.

The mission April 8 launched the third in a series of Shiyan 6-type satellites. The first two Shiyan 6 satellites launched on Long March 2D rockets from the Jiuquan space center in northwestern China in November 2018 and July 2020.

Shiyan means “experiment” in Chinese.

Unlike the smaller Long March 2D rocket, the Long March 4B rocket has a third stage to loft heavier payloads or deploy satellites into higher orbits. The first two Shiyan 6 satellites were deployed at lower altitudes than the spacecraft launched last week.

Artist’s concept of the Shiyan 6-03 satellite. Credit: China’s National Center for Nanoscience and Technology

The new Shiyan 6 satellite was built by the Institute of Microsatellite Innovation, part of the Chinese Academy of Sciences, officials said in a press release.

CASC, China’s top space contractor, said the new satellite will be “mainly used for space environment detection and related technology experiments.”

One of the technologies to be tested on the Shiyan 6 spacecraft is a new super-black coating designed to prevent stray light from disrupting optical cameras.

China’s National Center for Nanoscience and Technology said in a statement that the “nanocomposite” dark coating was installed on the Shiyan 6 satellite’s optical system. The dark material is designed to suppress stray light from the sun and Earth.

The coating will “greatly improve the satellite optical system’s ability to detect dim targets,” the center said.┬áThe super-black material will absorb 99.6% of ultraviolet, visible, and near-infrared light.

“Nanocomposite super-black coating material has broad application prospects in dim target detection, interstellar navigation, infrared stealth and other fields,” the center said.

Chinese officials did not disclose details about the optical system on-board the Shiyan 6 satellite, or any of the other experiments on the mission. Dim target detection capabilities can aid in applications such as tracking other satellites in orbit, a field known as space situational awareness.

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