samedi 25 août 2018

Long March 3B launches Beidou satellites












Beidou Navigation Satellite System logo.

August 24, 2018

Long March 3B carrying Beidou-3M11 and Beidou-3M12 launch

A new pair of navigation satellites were launched on Friday by China, marking its 23rd orbital launch this year. The launch of Beidou-3M11 and Beidou-3M12 took place from the LC3 Launch Complex of the Xichang Satellite Launch Center, Sichuan province, using a Long March-3B/Y1 (Chang Zheng-3B/Y1) launch vehicle. Launch time was 23:52 UTC and took around four hours to complete the mission.

BeiDou-3 satellites launched by Long March-3B

Also designated Beidou-35 and Beidou-36, the MEO satellites are the Medium Earth Orbit component of the third phase of the Chinese Beidou (Compass) satellite navigation system. The satellites are part of a fleet that will expand the system to a global navigation coverage.

Artist's view of a BeiDou-3 satellite by J. Huart

The satellites are using a bus that features a phased array antenna for navigation signals and a laser retroreflector, with a launch mass 1,014 kg. Spacecraft dimensions are noted to be 2.25 by 1.0 by 1.22 meters. Usually, the satellites reside in a 21,500 – 21,400 km nominal orbit at 55.5 degrees.

Three new pairs of Beidou-3M satellites are schedule to launch before years end. Beidou-3M13 and Beidou-3M14 will be launched in September, followed by Beidou-3M15 and M16 in October. Beidou-3M17 and Beidou-3M18 will be launched in November.

The Chinese Navigation Constellation

The Beidou Phase III system includes the migration of its civil Beidou 1 or B1 signal from 1561.098 MHz to a frequency centered at 1575.42 MHz – the same as the GPS L1 and Galileo E1 civil signals – and its transformation from a quadrature phase shift keying (QPSK) modulation to a multiplexed binary offset carrier (MBOC) modulation similar to the future GPS L1C and Galileo’s E1.

The Radio Navigation Satellite Service (RNSS) is very similar to that provided by GPS and Galileo and is designed to achieve similar performances.

For more information about Beidou navigation system: http://www.beidou.gov.cn/

For more information about China Aerospace Science and Technology Corporation (CASC): http://english.spacechina.com/n16421/index.html

Images, Video, Text, Credits: CASC/Beidou/SciNews/NASA Spaceflight.com/Rui C. Barbosa.

Greetings, Orbiter.ch

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