China launched a new geostationary remote sensing satellite from the renovated Xichang Satellite Launch Center on Sunday. A Long March-3B/G3 (Y3) – Chang Zheng-3B/G3 – rocket orbited the Gaofen-13 satellite, lifting off from the LC2 pad at 16:57 UTC.
The new satellite, possibly an improved version of the CAST developed Gaofen-4 orbited on December 28, 2015, is being designated as a high-orbit optical remote sensing satellite to be mainly used for land survey, crop yield estimation, environmental management, weather warning and forecast, and comprehensive disaster prevention and mitigation, providing information services for national economic development.
However, some rumors indicate that the new bird could also be an optical reconnaissance satellite operating in geostationary orbit.
For this mission, the launch vehicle underwent improvements involving the satellite fairing and cargo pressurized transport systems, along with other elements such as the rocket igniters and laser inertial group data.
This was the first launch in several weeks from the Xichang Satellite Launch Center due to modernization work.
The Long March-3B (Chang Zheng-3B) launch vehicle started in 1986 to meet the international satellite launch market’s demand, especially for high power and heavy communications satellites. Its development was based on the fight proven technology of Long March launch vehicles.
Developed from the Chang Zheng-3A, the Chang Zheng-3B is 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 four strap-on boosters in the core stage that provide additional help during the first phase of the launch.
The rocket can launch an 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 to launching heavy GEO communications satellites.
The rocket structure also combines all sub-systems and comprises four strap-on boosters, a first stage, a second stage, a third stage, and payload fairing.
The first two stages and 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 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 specific impulse at 3,092 m/s. The upper stage can 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. The first stage shutdown takes place at 1 minute 25 seconds into the flight.
The separation between the first and second stages occurs 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, followed by the vernier engines’ shutdown 15 seconds later.
The separation between the second and the third stage and the third stage’s ignition 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 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. However, no confirmation has been provided at this time.
The Xichang Satellite Launch Centre is situated in the Sichuan Province, southwestern 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.