China has launched another satellite into its navigation constellation.
The Long March-3A rocket was launched at 0458 local on 11 July (2058 UTC on 10 July) from the Xichang Satellite Launch Centre. It is the 32nd satellite in the BeiDou constellation - and one of the Beidou-2 family, the second-generation satellites. The third-generation was introduced in 2017, with 8 BeiDou-3 satellites already in orbit.
The Chief Designer explains that the launch of a backup BeiDou-2 satellite will ensure the system's continuous and stable operation.
BeiDou was formally launched in 1994, providing cover over China in 2000 and over the Asia-Pacific region by 2012.
But some of the BeiDou-2 satellites are nearing the end of their lives and need to be replaced by backups. China launched 2 backup satellites in March and June 2016. This new backup is not a simple repeat of previous satellites but, according to the designer, has been upgraded to improve its reliability and carries a rubidium clock.
China’s first navigation satellites used costly imported rubidium clocks but, after the launch of the BeiDou programme, the US banned exports of rubidium clocks to China. The Chief Designer stresses that China had to depend on itself; its first self-developed rubidium clock was tested on a satellite in September 2006, and the performance of the rubidium clocks is improved on BeiDou-2 satellites.
It is reported that this year will see an intensive launch of BeiDou satellites, being expected to provide navigation and positioning services in Eurasia by late 2018 and globally by 2020.
BeiDou-3 satellites will include signals that are compatible with other GNSS (GPS, GLONASS and Galileo) and will also provide satellite-based augmentation (SBAS), as well as SAR services. Positioning accuracy is quoted as 2.5-to-5 m.
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