CNSA conducted yesterday launch of Long March 3B rocket with latest weather satellite, Feng Yun-4A. Rocket took off at 16:11 UTC (00:11 local time on 12 December) from LC-3 complex at Xichang Satellite Launch Center.

Feng Yun-4A is first from series of six satellites representing Feng Yun-4 generation. It is based on SAST-5000 satellite bus and just as whole series, was designed to replace old Feng Yun-2 satellites. FY-4A was built by SAST and will be operated by  National Satellite Meteorological Center.

Satellite arrived to Xichang by plane on October 23 2016. After testing and performing checks, satellite was integrated with Long March 3B rocket inside assembling facility. Due the lack of live broadcast it is not much known on launch campaign. Yesterday rocket was already after rollout and was waiting for launch. Punctually at 16:11 UTC rocket started to rise over Launch Complex 3 at Xichang Satellite Launch Center. After pitch and roll maneuver rocket set its trajectory to SE to perform flight over Pacific. At T+2’20” four boosters were jettisoned; first core stage of the rocket was continuing powered flight for next 18 seconds until MECO at T+2’38”. Separation was followed by ignition of upper stage propulsion – YF-24B engine. Burn has lasted for three minutes during which rocket jettisoned its 4 m wide payload fairing. At around T+5’30” second stage was cut off and separated from upper stage. It started its YF-75 engine for two times. After reaching GTO orbit satellite was deployed at around T+26′. First confirmation of good condition of the spacecraft were announced one hour later. Launch was also confirmed by USSTRATCOM, which already described FY-4A after separation as 2016-077A (184 km x 35804 km orbit with inclination of 28.43°) and third stage as 2016-077B (remaining on lower orbit of 159 km x 34409 km, 28.49°).

Feng Yun-4A is weather satellite designed by Shanghai Academy of Spaceflight Technology. It is based on SAST-5000 bus and weighs 5380 kg. It is powered with single deployable solar array and onboard battery providing 3200 W of power for onboard devices. It is stabilized by 3 axis attitude control system. Dimensions with folded array are: 3.51 m x 3.28 m x 4.16 m. Satellite will operate from GEO orbit, from 99.5° East orbital slot.

FY-4A is representing optical version of FY-4 family. It is equipped with two main optical sensors: AGRI – Advanced Geosynchronous Radiation Imager – operating in 14 spectral channels used for Earth and cloud imaging. It offers impressive resolution varying from 0.5 km to 4 km. Second device is Lightning Mapping Imager (LMI), optical device for monitoring lightnings. Satellite is also equipped with  Geostationary Interferometric Infrared Sounder (GIIRS) to more advanced analysis of cloud clusters. For detecting and monitoring energetic levels of particles spacecraft was equipped with Space Environment Monitoring Instrument Package (SEMIP). Satellite is also able to receive data from placed on Earth weather sensors operating under Data Collection Service (DCS system) using UHF antenna. Satellite is using High and Low-Data Rate Direct Broadcast Capabilities. It gives opportunity to transmit data to users from instruments with rate of 150 kbps, High Data Rate Information is using three channels depending on instruments. Data from AGRI and LMI are transmitted with speed of 8 Mbps at frequency of 1681  MHz, resampled AGRI data are transmitted at frequency of 1679 MHz with 3 Mbps, GIIRS data are also transmitted on 1979 MHz but with lower speed at 1 Mbps.

Satellite was delivered to space by Long March 3B G2. G version is result of recent upgrades and it is most modern rocket from Long March 3 family. Its construction is based on Long March 3B with three stages and four strap-on boosters. Each booster is utilizing single YF-21C engine (2961.9 kN of thrust). First stage is powered by four identical YF-21C engines (2961.6 kN thrust each). Second stage is equipped in one central YF-24E (thrust at 742 kN) and four YF-23C (thrust at 47.1 kN) for stabilization. Third stage is equipped in one YF-75 engine generating 167.17 kN of thrust. Rocket is fully liquid fueled; boosters and first two stages are utilizing N2O4/UDMH, for the third stage LH2/LOX is utilized. Rocket is able to deliver to Low Earth Orbit 12 t of payload. Long March 3B G version is equipped with larger payload fairing, comparing to ordinary LM 3B. It is long for 10.4 m with diameter at 4 m; due this fact LM-3B G is longest among Long March 3 family with total length of 57.2 m (diameter is identical in all versions with 3.35 m).