Long March-3C lofts Beidou-2G8 (GEO-8)

A new navigation satellite was successfully launched by China on Friday. The launch of Beidou-2G8 (GEO-8) took place from the LC2 Launch Complex of the Xichang Satellite Launch Center, Sichuan province, using the Long March-3C/G2 (Y16) launch vehicle. Launch time was 15:49 UTC.

Also designated Beidou-45, the satellite is part of the GEO component of the 2nd phase of the Chinese Beidou (Compass) satellite navigation system, using both geostationary satellites and satellites in intermediate orbits.
The satellites are based on the DFH-3B Bus. This bus has a payload increased to 450 kg and payload power to 4,000 W.

The spacecraft feature a phased array antenna for navigation signals and a laser retroreflector and additionally deployable S/L-band and C-band antennas. With a launch mass of 4,600 kg, spacecraft dimensions are noted to be 2.25 by 1.0 by 1.22 meters.

Previous Beidou satellites were orbited on November 18, 2018, with a Long March-3B/YZ-1 launch vehicle launching the Beidou-3M17 (Beidou-42) and Beidou-3M18 (Beidou-43) satellites, and on April 20, 2019, with a Long March-3B/G2 orbiting the Beidou-3IGSO-1 (Beidou-44). Both launches took place from Xichang. The previous Beidou-2G satellite, Beidou-2G7 (Beidou-23), was launch on June 12, 2016.

The Beidou Navigation Satellite System (BDS) has been independently constructed, developed and operated by China taking into account the needs of the country’s national security, economic and social development. As a space infrastructure of national significance, BDS provides all-time, all-weather and high-accuracy positioning, navigation and timing services to global users.

Render of a BeiDou-3 satellite by J. Huart.

Along with the development of the BDS service capability, related products have been widely applied in communication, marine fishery, hydrological monitoring, weather forecasting, surveying, mapping and geographic information, forest fire prevention, time synchronization for communication systems, power dispatching, disaster mitigation and relief, emergency search and rescue, and other fields.

Navigation satellite systems are public resources shared by the whole globe, and multi-system compatibility and interoperability have become a trend. China applies the principle that “BDS is developed by China, and dedicated to the world”, serving the development of the Silk Road Economic Belt, and actively pushing forward international cooperation related to BDS.

As BDS joins hands with other navigation satellite systems, China will work with all other countries, regions and international organizations to promote global satellite navigation development and make BDS further serve the world and benefit mankind.

China started to explore a path to develop a navigation satellite system suitable for its national conditions, and gradually formulated a three-step development strategy: completing the construction of BDS-1 and provide services to the whole country by the end of 2000; completing the construction of BDS-2 and provide services to the Asia-Pacific region by the end of 2012; and to complete the construction of BDS-3 and provide services worldwide around 2020 with a constellation of 27 MEOs plus 5 GEOs and the existing 3 IGSOs satellites of the regional system. CNSS would provide global navigation services, similarly to the GPS, GLONASS or Galileo systems.

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 Phase II B1 open service signal uses QPSK modulation with 4.092 megahertz bandwidth centered at 1561.098 MHz.

The current Beidou constellation spacecraft are transmitting open and authorized signals at B2 (1207.14 MHz) and an authorized service at B3 (1268.52 MHz).

Real-time, stand-alone Beidou horizontal positioning accuracy was classed as better than 6 meters (95 percent) and with a vertical accuracy better than 10 meters (95 percent).

The Chinese Navigation Constellation – via beidou.gov.cn

CNSS supports two different kinds of general services: RDSS and RNSS. In the Radio Determination Satellite Service (RDSS), the user position is computed by a ground station using the round trip time of signals exchanged via GEO satellite. The RDSS long-term feature further includes short message communication (guaranteeing backward compatibility with Beidou-1), large volume message communication, information connection, and extended coverage.

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

The system is dual-use, based on a civilian service that will provide an accuracy of 10 meters in the user position, 0.2 m/s on the user velocity and 50 nanoseconds in time accuracy; and the military and authorized user’s service, providing higher accuracies.

This mission used the Long March 3C rocket.

The Long March-3C was developed to fill the gap between the Long March-3A and the Long March-3B, having a payload capacity of 3,800 kg for GTO or 9,100 kg for LEO. This is a three stage launch vehicle identical to the CZ-3B but only using two of the strap-on boosters on its first stage.

CZ-3C provides two types of fairing and two kinds of fairing encapsulating process and four different payload interfaces, which is the same as CZ-3B launch vehicle. The various fairing and interface adapter and the suitable launch capacity make CZ-3C a good choice for the user to choose the launch service.

The development of the CZ-3C started in February 1999. The rocket has a liftoff mass of 345,000 kg, sporting structure functions to withstand the various internal and external loads on the launch vehicle during transportation, hoisting and flight.

The rocket structure also combines all sub-systems together and is composed of two strap-on boosters, a first stage, a second stage, a third stage and payload fairing.

The first two stages, as well as the two strap-on boosters, use hypergolic (N2O4/UDMH) fuel while the third stage uses cryogenic (LOX/LH2) fuel. The total length of the CZ-3C is 54.838 meters, with a diameter of 3.35 meters on the core stage and 3.00 meters on the third stage.

On the first stage, the CZ-3C uses a DaFY6-2 engine with a 2961.6 kN thrust and a specific impulse of 2556.2 Ns/kg. The first stage diameter is 3.35 m and the stage length is 26.972 m.

Each strap-on booster is equipped with a DaFY5-1 engine with a 704.4 kN thrust and a specific impulse of 2556.2 Ns/kg. The strap-on booster diameter is 2.25 m and the strap-on booster length is 15.326 m.

The second stage is equipped with a DaFY20-1 main engine (742 kN / 2922.57 Ns/kg) and four DaFY21-1 vernier engines (11.8 kN / 2910.5 Ns/kg each). The second stage diameter is 3.35 m and the stage length is 9.470 m.

The third stage is equipped with two YF-75 engines developing 78.5 kN each and with a specific impulse of 4312 Ns/kg. The fairing diameter of the CZ-3C is 4.00 meters and has a length of 9.56 meters.

The Xichang Satellite Launch Centre is situated in the Sichuan Province, south-western China and is the country’s launch site for geosynchronous orbital launches.

Equipped with two launch pads (LC2 and LC3), the center has a dedicated railway and highway lead directly to the launch site.

The Command and Control Centre is located seven kilometers south-west of the launch pad, providing flight and safety control during launch rehearsal and launch.

Other facilities on the Xichang Satellite Launch Centre are the Launch Control Centre, propellant fuelling systems, communications systems for launch command, telephone and data communications for users, and support equipment for meteorological monitoring and forecasting.

The first launch from Xichang took place at 12:25UTC on January 29, 1984, when the Chang Zheng-3 (Y-1) was launched the Shiyan Weixing (14670 1984-008A) communications satellite into orbit.

What’s next for China in 2019?

Two days after the launch of Beidou-45, a Long March-4C launch vehicle will orbit the Yaogan Weixing-33 mission from the Taiyuan Satellite Launch Center. This will probably be a SAR military mission similar to previous ones launched from Taiyuan. Launch is scheduled for May 22.

In late May we may assist to the launch of the first fist of the private Jielong-1 carrying four satellites and on the first days of June the first launch of the private Shuang Quxian-1 carrying seven satellites. Both launches will take place from the Jiuquan Satellites Launch Center that will also be the launch site for the launch of the next generation recoverable satellite – Shijian-19 – at the end of June. The launch will be made using a Long March-2D launch vehicle.

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