Thursday, January 11, 2018

Long March 3B to Deliver Two BeiDou-3 Satellites into Orbit

Long March 3B launches with the BeiDou-3 duo (M1 and M2) on November 5, 2017. Photo Credit: Yang Zhiyuan / Xinhua

A Long March 3B booster is in its final stage of preparations for today’s flight tasked with delivering two BeiDou-3 satellites for China’s BeiDou Navigation Satellite System (BDS). The mission will begin around 23:00 GMT (6:00 p.m. EST), when the Long March 3B launch vehicle will thunder off from the Launch Complex 2 at the Xichang Satellite Launch Center (XSLC) in China’s Sichuan Province.

Chinese media remain silent about the mission and pre-launch preparations. It is only known that the launch was originally scheduled for November 2017, but was later delayed by one month. Finally, the mission was postponed once again, this time to January 2018, making it the second orbital flight for China this year.

Although Beijing has not disclosed any detailed information about the flight’s timeline, it is assumed that today’s mission, counting from liftoff to separation of the satellites, should last few hours as its goal is to place the satellites into a medium-Earth orbit (MEO). 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 BeiDou-3 duo into MEO.

The satellites that will be launched today are designated BeiDou-3 M3 and BeiDou-3 M4. They are based on a newly-developed dedicated satellite bus and weigh about one metric ton each. Both spacecraft have two deployable solar arrays and were designed to be operational for about 12 years. The duo will reside in MEO at an altitude of 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).

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 used in today’s flight is a 180-foot (55-meter) tall booster capable of launching up to 12 metric tons of payload to low-Earth orbit or 5 metric tons of cargo into a Geostationary Transfer Orbit (GTO). For some launches, this rocket could be optionally equipped with a Yuanzheng-1 upper stage.

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