China has launched a new communications satellite to provide real-time communications between orbiting satellites and ground control stations. Tianlian 2-01 was launched at 15:50 UTC Saturday from the LC2 Launch Complex of the Xichang Satellite Launch Center using a Long March-3B/G2 (Chang Zheng-3B/G2) launch vehicle.
The Chinese tracking and data relay satellites were developed by the China Academy of Space Technology (CAST) and it is similar to the American Tracking and Data Relay Satellite System (TDRSS) in concept. The system is designed to support near-real-time communications between orbiting spacecraft and the ground control, and will complement the ground-based space tracking and telemetry stations and ships to support future space projects.
This launch was already expected in 2018, but was pushed back to 2019. The Tianlian-2 satellite series represents the second generation of this series of satellites. Developed by the Chinese Academy of Space Technology (CAST), the satellite is based on the DFH-4 satellite platform.
DFH-4 is the third generation communications satellite bus in China with high power, strong payload capacity and extended service life. It consists of a propulsion module, service modules and solar arrays.
Its dimensions are 2360mm×2100mm×3600mm, with a liftoff mass of 5,200 kg. Solar Array Power is 10.5 kW (EOL) and payload power is 8 kW. The platform can be equipped with C, Ku, Ka and L transponders. It uses a 3-axis stabilization mode and its station keeping precision is west/east ±0.05° and north/south ±0.05°. Antenna Pointing Precision＜0.1°. A service lifetime in orbit is expected to last 15 years.
The first generation Tianlian satellites were launched between 2008 and 2016, supporting different kinds of missions and especially the ones related to the Chinese manned space program. The satellites were based on the CAST’s DFH-3 satellite platform.
The first satellite of the series, Tianlian 1-01 (32779 2008-019A) was launched on April 25, 2008, using the very first Long March-3C launch vehicle – CZ-3C Chang Zheng-3C (Y1). Launch took place at 15:35:07.852UTC from the LC2 launch complex at the Xichang Satellite Launch Center. Tianlian 1-02 (37737 2011-032A) followed on July 11, 2011, with the satellite being orbited by the Long March (Y8) at 15:41:03.700UTC, also from the LC2 launch complex.
Tianlian 1-03 (38730 2012-040A) was launched at 15:43:03.769UTC on July 25, 2012, using the Long March-3C (Y9) and the fourth – and last – satellite of the first generation, Tianlian 1-04 (41869 2016-072A), was launched on November 22, 2016, using the Long March-3C/G2 (Y13) rocket at 15:24:04.194UTC.
To meet demand of international satellite launch market, especially for high power and heavy communications satellites, the development of Long March-3B (Chang Zheng-3B) launch vehicle was started in 1986 on the basis of the fight proven technology of Long March launch vehicles.
Developed from the Chang Zheng-3A, the Chang Zheng-3B is at the moment the most powerful launch vehicle on the Chinese space launch fleet.
The CZ-3B features enlarged launch propellant tanks, improved computer systems, a larger 4.2 meter diameter payload fairing and the addition of four strap-on boosters in the core stage that provide additional help during the first phase of the launch.
The rocket is capable of launching a 11,200 kg satellite to a low Earth orbit or a 5,100 kg cargo to a geosynchronous transfer orbit.
The CZ-3B/G2 (Enhanced Version) launch vehicle was developed from the CZ-3B with a lengthened first core stage and strap-on boosters, increasing the GTO capacity up to 5,500kg.
On May 14, 2007, the first flight of CZ-3B/G2 was performed successfully, accurately sending the NigcomSat-1 into pre-determined orbit. With the GTO launch capability of 5,500kg, CZ-3B/G2 is dedicated for launching heavy GEO communications satellite.
The rocket structure also combines all sub-systems together and is composed of four strap-on boosters, a first stage, a second stage, a third stage and payload fairing.
The first two stages, as well as the four strap-on boosters, use hypergolic (N2O4/UDMH) fuel while the third stage uses cryogenic (LOX/LH2) fuel. The total length of the CZ-3B 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-3B uses a YF-21C engine with a 2,961.6 kN thrust and a specific impulse of 2,556.5 Ns/kg. The first stage diameter is 3.35 m and the stage length is 23.272 m.
Each strap-on booster is equipped with a YF-25 engine with a 740.4 kN thrust and a specific impulse of 2,556.2 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 YF-24E (main engine – 742 kN / 2,922.57 Ns/kg; four vernier engines – 47.1 kN / 2,910.5 Ns/kg each). The second stage diameter is 3.35 m and the stage length is 12.920 m.
The third stage is equipped with a YF-75 engine developing 167.17 kN and with a specific impulse of 4,295 Ns/kg. The fairing diameter of the CZ-3B is 4.00 meters and has a length of 9.56 meters.
The CZ-3B can also use the new Yuanzheng-1 (“Expedition-1″) upper stage that uses a small thrust 6.5 kN engine burning UDMH/N2O4 with a specific impulse at 3,092 m/s. The upper stage is able to conduct two burns, having a 6.5 hour lifetime and is capable of achieving a variety of orbits. This upper stage was not used on this launch.
Typical flight sequence for the CZ-3B/G2 sees the launch pitching over 10 seconds after liftoff from the Xichang Satellite Launch Centre.
Boosters shutdown 2 minutes and 7 seconds after liftoff, separation from the first stage one second latter. First stage shutdown takes place at 1 minute 25 seconds into the flight.
Separation between the first and second stage takes place at 1 minute 26 seconds, following fairing separation at T+3 minutes 35 seconds. Stage 2 main engine shutdown occurs 326 seconds into the flight, following by the shutdown of the vernier engines 15 seconds later.
Separation between the second and the third stage and the ignition of the third stage takes place one second after the shutdown of the vernier engines of the second stage. The first burn of the third stage will last for 4 minutes and 44 seconds.
After the end of the first burn of the third stage follows a coast phase that ends at T+20 minutes and 58 seconds with the third stage initiating its second burn. This will have a 179 seconds duration. After the end of the second burn of the third stage, the launcher initiates a 20 second velocity adjustment maneuver. Spacecraft separation usually takes place at T+25 minutes 38 seconds after launch.
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 fueling 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 (Y1) was launched the Shiyan Weixing (14670 1984-008A) communications satellite into orbit.