BEIDOU GNSS Constellation

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jimh
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BEIDOU GNSS Constellation

Postby jimh » Wed Nov 20, 2019 10:19 am

On November 4, 2019, China launched another global navigation satellite system (GNSS) BEIDOU space vehicle into a transfer orbit, where it will eventually lift itself with onboard propulsion into an inclined geo-synchronous orbit. (IGSO) This satellite is latest-generation BDS-3 model, and it is the 49th satellite launched in the BEIDOUO program. According to news sources in China, six more launches of BEIDOU satellites are planned, including two more within a month.

The BEIDOU constellation is a mix of three orbital types.

The medium Earth orbit (MEO) BEIDOU satellites circle the globe with orbital periods of periods of 12.89-hours, similar to GPS and GALILEO satellites at an orbital height of 27.878-km (17,322-miles) and inclined 55-degrees to the equator. At present BEIDOU appears to have 15 satellites in medium Earth orbit.

The Geo-stationary orbit (GEO) satellites remain in a stationary location at the equator at a orbital height of 42,164-km ( 26,200-miles). At present BEIDOU appears to five GEO satellites at 58.85, 80, 110.5, and 140, and 144.5-degrees East longitude.

The inclined geo-synchronous orbit (IGSO) satellites have an orbital period of one sidereal day and orbital height of 42,164-km ( 26,200-miles).The orbit is inclined relative to the equator 55-degrees. From a ground observer they appear to have a figure-8 motion (analemma) in the sky as they move north and south of the equator in their orbits. At present BEIDOU appears to have five satellites in IGSO at 95-degrees-East longitude and 55-degree inclination, and three in IGSO at 118-degree-East longitude and 55-degree inclination, for a total of eight in IGSO. Some may be older satellites destined for replacement.

Cf.: https://www.gpsworld.com/the-almanac/#beidou

This most recent satellite was launched atop a Long March 3B rocket from the Xichang space center in southwest Sichuan province. The Long March 3B rocket has been flown 317 times. China has launched 24 satellites (of various types) in 2019 so far.

When at fully-operational status, the BEIDOU constellation will have 35 satellites: 27 satellites in MEO, five in GEO, and three in IGSO, according to one informed observer.

More at: http://en.beidou.gov.cn/WHATSNEWS/201911/t20191112_19433.html

The number of BEIDOU satellites in view (with 5-degree elevation mask) is shown in the graphic below. As intended, the system's primary coverage is over China, but six to eight BIEDOU satellites should be in view over the central USA at most times.

BEIDOU_SatellitesInView.jpg
Fig. 1. Density plot of BEIDOU satellites in view on a Mercator projection of the Earth; valid at November 20, 2019,
BEIDOU_SatellitesInView.jpg (99.52 KiB) Viewed 771 times


I don't know of any particular recreational-grade marine GNSS receivers that utilize BEIDOU. Many low-cost smartphones that are made in China and intended for sale in China are now provided with GNSS receivers that can use BEIDOU. The government of China may require all cars sold in China to have a BEIDOU navigation system; one source mentions 2020 as the year for this requirement to be implemented.

For an interesting and very thorough discussion of BEIDOU read this 2017 white paper:

China’s Alternative to GPS and its Implications for the United States