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Chinese Long March 4B sends trio of Earth-observing satellites aloft

China’s Long March 4B rocket launches Ziyuan-3 No. 2 and two ÑuSat satellites into space.

China’s Long March 4B rocket launches Ziyuan-3 No. 2 and two ÑuSat satellites into space. Photo Credit: Xinhua

A Chinese Long March 4B launch vehicle took to the skies on Sunday, May 29, at 11:17 p.m. EDT (03:17 GMT on Monday, May 30), on a mission to orbit the country’s Ziyuan-3 No. 2 high-resolution remote sensing satellite and two commercial ÑuSat Earth-observing spacecraft for Argentina. Liftoff took place from Launch Site 9 at the Taiyuan Satellite Launch Center located in China’s Shanxi Province.

After liftoff, the Long March 4 rocket began its vertical ascent powered by its YF-21B booster that consists of four YF-20B engines. These engines burned for nearly three minutes until the first stage separation occurred.

The rocket’s second stage continued the flight for slightly more than two minutes. The separation of the second stage occurred about five minutes after liftoff. Afterward, the third stage took control over the mission, burning for approximately six minutes until the satellites were deployed into orbit.

China’s Long March 4B rocket launches Ziyuan-3 No. 2 and two ÑuSat satellites into space.

China’s Long March 4B rocket launches Ziyuan-3 No. 2 and two ÑuSat satellites into space. Photo Credit: Xinhua

Ziyuan-3 No. 2, developed jointly by the China’s Academy of Space Technology (CAST) and the Beijing Institute of Spacecraft System Engineering, is the country’s third generation Earth-observing satellite for civilian purposes. It is scheduled to be operated by the Ministry of Land and Resources for up to five years.

Weighing about 2.6 metric tons, the spacecraft features two deployable solar arrays and is fitted with three high-resolution panchromatic cameras and an infrared multispectral scanner. The cameras are capable of covering a 32-mile (51-kilometer) wide swath on the ground, reaching a resolution of 6.9 to 8.2 feet (2.1 to 2.5 meters). The scanner has a spectral resolution of 19.7 feet (6 meters) and a 32-mile (51-kilometer) ground swath.

Residing in a Sun-synchronous polar orbit (SSO) at an altitude of some 314 miles (506 kilometers), inclined 97.4 degrees, the satellite is being fielded to conduct surveys on land resources, to help with natural disaster-reduction and prevention, as well as to lend assistance to farming, water conservation, urban planning, and other sectors.

The first Ziyuan satellite was launched in 1999 to initiate China’s Earth Observation Program. Besides civilian purposes, the first two generations of Ziyuan spacecraft were also used to conduct military reconnaissance.

Piggybacking on this mission are two small Argentinian satellites. Designated ÑuSat-1 and ÑuSat-2, these box-sized spacecraft are part of the Aleph-1 constellation of Earth-observing satellites for commercial customers. Nicknamed “Fresco” and “Batata”, these two spacecraft were developed by Satellogic S.A. who will also operate the satellite duo.

“We have confirmation from the ground station in Bariloche: Fresco and Batata are healthy and sending strong signals. The launch is 100 percent success,” Emiliano Kargieman of Satellogic S.A. tweeted shortly after the spacecraft were successfully inserted into SSO at an altitude of 310 miles (500 kilometers), and inclined 97.5 degrees.

Each satellite weighs about 81.5 lbs (37 kg) and measures approximately 1.31 by 1.41 by 2.46 feet (40cm × 43cm × 75cm). The ÑuSat spacecraft are equipped with an imaging system capable of operating in visible and infrared light. The systems that these spacecraft are equipped with enables them to generate still imagery and video of Earth at a ground resolution of up to 3.3 feet (one meter). The two satellites will also carry a U/V linear transponder to offer services for the HAM radio community.

The three-stage Long March 4B carrier rocket employed for this launch has served China for some time. It was designed to deliver satellites into low-Earth (LEO) and Sun-synchronous orbits. The 150 ft (46 meters) tall launch vehicle has been in service for more than 16 years and has conducted 27 missions – with only one of them ending unsuccessfully.

With a mass of 249 tonnes, the Long March 4B booster is capable of delivering up to 4.2 tonnes to LEO, 2.8 tonnes to SSO, and 1.5 tonnes to a geostationary transfer orbit (GTO). The rocket’s first stage is 91.5 ft (28 m) long and has 11 feet (3.35 m) in diameter. It is powered by four YF-20B engines. The second stage, 35 ft (11 m) long and 11 ft (3.35 m) in diameter, is equipped with one YF-22C main engine and four YF-23C vernier engines. The 49 ft (15 m) long third stage measures 9.5 ft (2.9 m) in diameter and is powered by two YF-40 engines.

Sunday’s liftoff was the 228th mission for the Long March family of launch vehicles. This mission was also the first flight of the Long March 4B this year as well as the first liftoff from the Taiyuan Satellite Launch Center in 2016. So far, the country has launched six missions this year – all of them successful.

China’s next flight is currently planned for June 27, 2016, when a new version of the Long March booster, the Long March 7, will conduct its maiden flight. It will also be the first flight conducted from the Wenchang Satellite Launch Center, located on Hainan Island, in southern China. China has undertaken an ambitious flight manifest for 2016 – with over 20 missions slated to take place this year.


Tomasz Nowakowski is the owner of Astro Watch, one of the premier astronomy and science-related blogs on the internet. Nowakowski reached out to SpaceFlight Insider in an effort to have the two space-related websites collaborate. Nowakowski's generous offer was gratefully received with the two organizations now working to better relay important developments as they pertain to space exploration.

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