A Chinese Long March 4C has launched the Queqiao spacecraft – a relay satellite for the upcoming Chang’e-4 lunar mission. Launch occurred from the LC-3 pad at the Xichang Satellite Launch Centre (XSLC) at 21:25 UTC.
This latest launch is part of China’s growing ambitions for lunar exploration, which has already achieved numerous successes. Chang’e-1 was launched in 2007 and and Chang’e-2 in 2010.
The previous mission involved the Chang’e-3 probe and Yutu lunar rover. Chang’e is the name of the Chinese moon goddess.
The mission, from the trip to the Moon, the landing on the lunar surface and the Rover’s – nicknamed Jade Rabbit – short road trip, all captivated the Chinese public and fostered their support for China’s future exploration goals.
Now preparations are in full swing to move on to the Chang’e-4 mission that is set to take place later this year. Once again it will involve a lander and a rover.
However, there will also be a variety of international payloads riding along with this mission, some of whom will have been attracted by the success of the previous expedition.
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The landing site for this mission is expected to be the Von Kármán crater in the South Pole-Aitken Basin. If successful, this will be the first spacecraft to land on the far side of the Moon.
As such, a communication relay will be required to communicate with Earth.
Queqiao will provide that role. Launched to an eventual L2 Halo Orbit (Earth-Moon L2 Lagrange Point), the satellite will have a lifetime of five years, covering both this and potentially another Chang’e mission.
The spacecraft is based on the CAST100 small satellite platform, with commonality to the often used DFHSat system that finds its way on to a number of Chinese spacecraft. It has a mass of 425kg and uses a hydrazine propulsion system.
It will transmit telemetry back to Earth via its S-band antenna, while X-band data will provide the communication path between the lander and rover.
More robotic missions are planned and despite China’s solid progression with its crewed program, a crewed lunar landing is still around 15 years away.
There were reports of two microsatellites joining this mission, providing a combination of radio astronomy and amateur radio outreach work – which enthusiasts would be able to download telemetry and images. These satellites would be set into an elliptical lunar orbit.
They are understood to be called DSLWP-A1/A2, with a mass of 45kg. They were also provided with names, Longjiang No. 1 and No. 2.
While Queqiao or ‘magpie bridge’ comes from Chinese mythology. Longjiang means ‘Dragon River’.
The rocket that launched this mission was the Long March 4C.
With its main commonality matched to the Long March-4B, the 4C first stage has a 24.65 meter length with a 3.35 meter diameter, consuming 183,340 kg of N2O4/UDMH (gross mass of first stage is 193.330 kg).
The vehicle is equipped with a YF-21B engine 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 38,326 kg, consuming 35,374 kg of N2O4/UDMH.
It includes a YF-22B main engine capable of a vacuum thrust of 742 kN and four YF-23B vernier engines with a vacuum thrust of 47.1 kN (specific impulses of 2,922 Ns/kg and 2,834 Ns/kg, respectively).
The third stage has a 4.93 meter length with a 2.9 meter diameter, consuming 12,814 kg of N2O4/UDMH. Having a gross mass of 14,560 kg, it is equipped with a YF-40 engine capable of a vacuum thrust of 100.8 kN and a specific impulse in a vacuum of 2,971 Ns/kg.
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.