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24.04.2018

China's Chang'e-4 relay satellite named "Queqiao"

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The relay satellite for the Chang'e-4 lunar probe expected to land on the far side of the Moon later this year, has been named "Queqiao" -- magpie bridge.

The name was announced by the China National Space Administration (CNSA)Tuesday, China's Space Day.

In a Chinese folktale, magpies form a bridge with their wings on the seventh night of the seventh month of the lunar calendar to enable Zhi Nu, the seventh daughter of the Goddess of Heaven, to cross and meet her beloved husband, separated from her by the Milky Way.

Together with the relay satellite, two microsatellites developed by the Harbin Institute of Technology, "Longjiang-1" and "Longjiang-2," will also be sent into orbit.

Work on Chang'e-4 is progressing well, said Li Guoping, a spokesman for CNSA.

Chang'e-4 will carry payloads for Germany, the Netherlands, Saudi Arabia and Sweden.

The far side of the Moon is of great scientific interest but landing there requires a relay satellite to transmit signals.

One of China's planned 36 launches this year, the relay satellite will be sent into the halo orbit of the Earth-Moon Lagrange Point L2 in late May, and the Chang'e-4 lunar lander and rover will be sent to the Aitken Basin of the south pole region of the Moon about six months later.

"We designed an orbit at the Earth-Moon Lagrange Point L2 about 450,000 kilometers from the Earth, where a gravitational equilibrium can be maintained, and the relay satellite will be able to 'see' both the Earth and the far side of the Moon," said Bao Weimin, director of the Science and Technology Commission of the China Aerospace Science and Technology Corporation.

The Aitken Basin is an ancient lunar region containing lots of primeval information, and as the far side of the Moon is shielded from electromagnetic interference from the Earth, it is an ideal place to study the space environment. The probe can "listen" to the deeper reaches of the cosmos, said Bao.

The relay satellite will be carried by Long March-4 rocket. The relay satellite and rocket are both at the launch center in Xichang, southwest China's Sichuan Province.

"The whole mission is very complex and challenging. We feel great pressure, but we are confident," Bao said.

Quelle: Xinhua

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Chang'e-4 lunar far side satellite named 'magpie bridge' from folklore tale of lovers crossing the Milky Way

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A rendering of the Chang'e-4 relay satellite, to launch in May 2018, and lander and rover to set down on the lunar far side in late 2018. Chinese Academy of Sciences

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China's Chang'e-4 relay satellite, which will launch next month to facilitate communications with a lander and rover on the lunar far side, has been named Queqiao - or magpie bridge - from a Chinese myth.

The name was announced by the China National Space Administration (CNSA) in Harbin, northeast China, on Tuesday April 24 at an event marking the advent of China's third Space Day.

The name comes from the Chinese myth and love story of the Weaver Girl and the Cowherd. Separated by the Silver River, which symbolises the Milky Way, the lovers are reunited for one day each year by a bridge formed by a flock of magpies - Queqiao (鹊桥) - allowing them to cross the heavens.

Two microsatellites, which will accompany the launch in May and be placed in lunar orbit, also received names.

These are Longjiang-1 and Longjiang-2 (龙江一号 and 龙江二号), meaning Dragon River 1 and 2. The developer of the microsatellites is the Harbin Institute of Technology, situated in the capital of Heilongjiang (Black Dragon River) Province. The Heilongjiang river is also known as the Amur.

Star-crossed lovers Niulang and Zhinu are permitted to be together one day a year, during the Qixi Festival. The painting is in the Long Corridor of the Summer Palace in Beijing.

 

 

Star-crossed lovers Niulang and Zhinu are permitted to be together one day a year, during the Qixi Festival. The painting is in the Long Corridor of the Summer Palace in Beijing. Public Domain

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Queqiao relay satellite

Chang'e-4 is a mission which will attempt the first-ever soft-landing on the far side of the Moon with a lander and rover in late 2018.

As the lunar far side never faces the Earth, a relay satellite is required to be in place to facilitate communications between terrestrial ground stations and the Chang'e lander and rover.

It is planned to launch from the Xichang Satellite Launch Centre on May 21 via a Long March 4C rocket.

The Queqiao relay satellite is based on a small satellite platform developed by the China Academy of Space Technology (CAST), and equipped with modified and newly developed components in order to meet the extra challenges posed by its mission requirements.

The satellite will operate in a halo orbit around the gravitationally stable second Earth-Moon Lagrange Point, more than 60,000 kilometres away from the lander and rover on the lunar far side.

Launch profile for the Chang'e-4 communications relay satellite.

 

 

Launch profile for the Chang'e-4 communications relay satellite. Chinese Academy of Sciences

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The distance will be around twice that of satellites in geosynchronous Earth orbit for terrestrial communications, while also being close to half a million kilometres from Earth, meaning greater power demands.

The halo orbit will allow Queqiao to be accessible to both ground stations on Earth and the lander on the lunar far side at times.

Image demonstrating a halo orbit around the second Earth-Moon Lagrange point, from which the Chang'e-4 communications relay satellite will operate.

 

 

Image demonstrating a halo orbit around the second Earth-Moon Lagrange point, from which the Chang'e-4 communications relay satellite will operate. NAOC/CAS

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It will reach this point some eight or nine days after launch from Xichang via a lunar swing-by. Once in its planned orbit, the satellite will carry out tests for its communications relay role and begin its science experiments.

As well as its main communications role, the relay satellite will carry the Netherlands-China Low-Frequency Explorer (NCLE) for low-frequency radio astronomy experiments.

The Longjiang-1 and 2 microsatellites, meanwhile, will test low frequency radio astronomy and space-based interferometry, as well as amateur radio activities. It will also carry a small optical camera developed by Saudi Arabia.

Testing on the Chang'e-4 DSLWP-A1 and DSLWP-A2 microsatellites in early 2018.

 

 

Testing on the Chang'e-4 DSLWP-A1 and DSLWP-A2 microsatellites in early 2018. CCTV/Youtube/Framegrab

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Landing, roving and preparing

The lander and rover for the mission, launching late this year, were originally manufactured at the same time as the Chang'e-3 spacecraft, which landed on the Moon in late 2013, in order to provide a backup mission.

Now repurposed for objectives on the lunar far side, the pair have recently been progressing through space environment tests.

Five of the science payloads, including the cameras, radar and imaging spectrometer noted below, are inherited from the 2013 Chang'e-3 mission, but new and international payloads will also travel.

Chang'e-3, which landed on the Moon in December 2013. Chang'e-4, initially slated as a backup mission, will launch by 2020.

 

 

Chang'e-3, which landed on the Moon in December 2013. Chang'e-4, initially slated as a backup mission, will launch by 2020. CNS

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The lander will carry a Landing Camera (LCAM), Terrain Camera (TCAM), Low Frequency Spectrometer (LFS), and Lunar Lander Neutrons and Dosimetry (LND), all of which were developed in Germany.

The rover will be equipped with a Panoramic Camera (PCAM), a Lunar Penetrating Radar (LPR), a Visible and Near-Infrared Imaging Spectrometer (VNIS), and an Advanced Small Analyser for Neutrals (ASAN), all from Sweden.

TCAM and PCAM on Chang'e-3 returned astounding images from Mare Imbrium.

Quelle: gbtimes

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