Thursday, February 8, 2018

China to Launch Another Duo of BeiDou-3 Navigation Satellites on Sunday

Long March 3B lifts off with two BeiDou-3 satellites on January 11, 2018. Photo Credit: Xinhua/Liang Keyan

China is gearing up to launch the latest duo of BeiDou-3 satellites into space atop its Long March 3B booster on Sunday, February 11. The liftoff, planned to be conducted at around 5:10 GMT (0:10 a.m. EST) from the Xichang Satellite Launch Center (XSLC), will mark the third launch of a BeiDou-3 doublet in just three months.

BeiDou-3 M3 and M4 spacecraft, which are slated to be launched on Sunday, were initially planned to be orbited on January 11. However, China decided to send BeiDou-3 M7 and M8 on that day instead of M3 and M4.

Sunday’s mission, like most Chinese orbital launches is shrouded in secrecy as Beijing does not inform the public about pre-launch preparations and does not offer any details regarding Long March 3B’s flight to orbit.

However, given that BeiDou-3 M satellites are designed to reside in a medium-Earth orbit (MEO), the mission should last few ours in order to place the payload into a desired orbital spot. On Sunday, the Long March 3B rocket will fly in a configuration with the Yuanzheng-1 (YZ-1) upper stage, which is expected to ignite its YF-50D engine some 20 minutes after liftoff and should burn out about six hours into the flight, deploying the two passengers into MEO.

BeiDou-3 M3 and BeiDou-3 M4 are based on a newly-developed dedicated satellite bus and weigh about one metric ton a piece. Both spacecraft have two deployable solar arrays and were designed to be operational for about 12 years. The duo will offer its services from MEO at an altitude of some 13,360 miles (21,500 kilometers), inclined 55.5 degrees.

BeiDou-3 M3 and M4 satellites represent the third phase of the BDS system (BeiDou-3). It is the final stage of the establishment of a Chinese space-based navigation architecture. The constellation will consist of 27 BeiDou-3M satellites in MEO, five BeiDou-3G satellites in a geostationary orbit (GTO), and three BeiDou-3I satellites in an inclined geosynchronous satellite orbit (IGSO).

China’s busy launch manifest of 2018, which envisions around 35-40 missions, includes 18 BeiDou-3 satellites, according to Yang Changfeng, chief designer of the BeiDou system.

"The intensive launches will pose a great challenge. We must exercise strict control over quality specifications to ensure each of them is a success," Yang said last month.

Named after the Chinese term for the Plough or the Big Dipper constellation, the BeiDou project was formally launched in 1994. The first BeiDou satellite was not launched until 2000, however. Nonetheless, by 2012, a regional network had already taken shape, which provided positioning, navigation, timing, and short message services in China and several other Asian countries. First BeiDou-3 satellite was launched in March 2015.

The three-stage Long March 3B rocket that will be used for Sunday's flight is a 180-foot (55-meter) tall launch vehicle capable of sending up to 12 metric tons of payload to low-Earth orbit or 5 metric tons of cargo into GTO. For some launches, this rocket could be optionally equipped with a Yuanzheng-1 upper stage.

Sunday’s mission will be the third launch of a BeiDou-3 duo within a time span of three months. On November 5, 2017, China launched BeiDou-3 M1 and M2, while on January 11, 2018 M7 and M8 satellites were orbited.

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