China continues to upgrade its oceanic surveillance systems with the launch of three new satellites from the Jiuquan Satellite Launch Center. The Group 04 of Yaogan Weixing-31 satellites launched at 02:20 UTC on 13 March from launch pad 94 of the LC-43 launch complex on a Chang Zheng 4C rocket.
As usual, Chinese media refer to the new satellites as being used “for electromagnetic environment surveys and other related technology tests,” and the mission is similar to the Yaogan-31 Group 01, Group 02, and Group 03 launched on April 10, 2018 and January 29 and February 24, 2021.
This designation of the Yaogan Weixing series is used to hide the true military nature of the satellites. In this case, the three satellites are orbited in a flying formation like a type of NOSS (Naval Ocean Surveillance System, considered as the Jianbing-8 military series.
Designed for locating and tracking foreign warships, the satellites will collect optical and radio electronic signatures of the maritime vessels as well as other information valuable for the Chinese maritime forces.
This satellite arrangement determines the location of radio and radar transmitters using triangulation and can identify naval units by analyzing the operating frequencies and transmission patterns detected.
And…the Chinese pulled a mini-Starlink here (a.k.a. "Keeping the Launch Cadence" – @Arianespace) with this successfully launched an hour ago at 02:19 UTC.https://t.co/RH24UWyQbQ pic.twitter.com/L3P0QEOl4L
— Cosmic Penguin (@Cosmic_Penguin) March 13, 2021
Overall, this was the 363rd mission of the Chang Zheng family of launch vehicles.
With its main commonality matched to the Chang Zheng 4B, the 4C’s first stage has a 27.9 meter length, a 3.35 meter diameter, and holds 183,340 kg of N2O4/UDMH (dinitrogen tetroxide/unsymmetrical dimethylhydrazine).
The stage is equipped with four YF-21C engines capable of a ground thrust of 2,971 kN and a ground-specific impulse of 2,550 Ns/kg.
The second stage has a 10.40 meter length with a 3.35 meter diameter and holds 52,700 kg of N2O4/UDMH.
It includes a YF-22C main engine capable of a vacuum thrust of 742 kN and four YF-23C vernier engines with a vacuum thrust of 47.1 kN. They have specific impulses of 2,922 Ns/kg and 2,834 Ns/kg, respectively).
The third stage has a 14.79 meter length with a 2.9 meter diameter and holds 12,814 kg of N2O4/UDMH. Having a gross mass of 14,560 kg, it is equipped with a YF-40A engine capable of a vacuum thrust of 100.8 kN and a specific impulse in a vacuum of 2,971 Ns/kg.
The Jiuquan Satellite Launch Center, in Ejin-Banner – a county in Alashan League of the Inner Mongolia Autonomous Region – was the first Chinese satellite launch center and is also known as the Shuang Cheng Tze launch center.
The first orbital launch took place on April 24, 1970 when the Chang Zheng 1 rocket launched the first Chinese satellite, the Dongfanghong-1.
The site includes a Technical Center, two Launch Complexes, Mission Command and Control Center, Launch Control Center, propellant fuelling systems, tracking and communication systems, gas supply systems, weather forecast systems, and logistics support.
Jiuquan was originally used to launch scientific and recoverable satellites into medium or low Earth orbits at high inclinations. It is also the place from where all the Chinese crewed missions are launched.
A Chang Zheng 4C ignites its four YF-21C first stage engines seconds before liftoff. (Credit: Xinhua)
The LC-43 launch complex, also known as South Launch Site (SLS), is equipped with two launch pads: 91 and 94. Launch Pad 91 is used for the crewed program to launch the Chang Zheng 2F launch vehicle with Shenzhou and Tiangong.
Launch Pad 94 is used for uncrewed orbital launches of the Chang Zheng 2C, 2D, and Chang Zheng 4C launch vehicles.
Other launch zones at the launch site are used for solid propellant launch vehicles.
Gearing up for crewed spaceflight
At Jiuquan, launch preparations continue for the upcoming Shenzhou-12 crewed mission, presently scheduled for June. This launch will take place after the orbital insertion of the Tianhe-1 base of the Tiangong modular orbital station.
Tianhe-1’s launch is presently anticipated for April 29, followed in May by the launch of the Tianzhou-2 (TZ-2) cargo vehicle. TZ-2 will automatically dock to Tianhe-1 a few days after launch in an orbital ballet that was rehearsed in April and June 2017 when Tianzhou-1 docked with the Tiangong-2 space station.
The Chinese space station. (Credit: China Manned Space)
At this time, 12 taikonauts are preparing for missions that will be important for establishing a permanent occupation of Tiangong in orbit.
Shenzhou-12 will stay in orbit for several months, but it is uncertain if the three taikonauts of the mission will deliver the new station to the Shenzhou-13 crew launching in October in a direct handover or if they will return before the next crew launches.
The Shenzhou-12 mission will mostly test the new space station’s systems, installing new hardware transported by the Tianzhou-2 and preparing Tianhe-1 for the arrival of future modules (Wentian and Mengtian) scheduled for launch in 2022.