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.
7.05.2018
China's Yuanwang 7 space tracking vessel after completing tasks related to the launch of the Tianzhou-1 cargo spacecraft in April 2017. CNS
China's Yuanwang 7 space tracking vessel is heading for waters in the Pacific Ocean ready to support the launch of the relay satellite which will facilitate the Chang'e-4 lunar far side lander and rover mission.
Yuanwang 7 is China's newest space tracking ship, which launched in July 2016 and was involved in the Shenzhou-11 mission, the debut flight of the heavy-lift Long March 5, and the Tianzhou-1 cargo spacecraft launch.
Having just assisted in the launch of the Apstar-6C satellite from Xichang on Friday, Yuanwang 7 is now sailing for an undisclosed location to support the launch of the Queqiao communications relay satellite, the Chinese language Science and Technology Daily reports.
The satellite is scheduled to launch from the Xichang Satellite Launch Centre on May 21 via a Long March 4C rocket, heading for an orbit beyond the Moon.
The Yuanwang ships, whose name means 'long view', are equipped with an array of dishes and electronics to support the launching and tracking of space launch vehicles. They observe trajectories and provide survey and control capabilities as rockets fly downrange.
Shortly after launch of the crewed Shenzhou-11 mission, Yuanwang 7 tracked the spacecraft for nearly 400 seconds and issued orders for the unfolding of solar panels and antenna, and perform other movements after entering orbit.
Yuanwang 7 Maritime Tracking of Shenzhou-11 Completed
Lunar far side pioneer
The launch of the Queqiao satellite, scheduled for May 21, is a precursor to the Chang'e-4 lander and rover mission, which will attempt the first-ever soft-landing on the far side of the Moon in late 2018.
The relay satellite is required to be in place to facilitate communications between terrestrial ground stations and the Chang'e-4 lander and rover. Its intended halo orbit around the second Earth-Moon Lagrange point more than 60,000 kilometres beyond the Moon will make it accessible to both ground stations on Earth and the lander on the lunar far side at all times.
Queqiao means 'magpie bridge' and comes from the Chinese myth and love story of the Weaver Girl and the Cowherd.
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.
Two microsatellites, named Longjiang-1 and Longjiang-2 (龙江一号 and 龙江二号), meaning Dragon River 1 and 2, will also be aboard for launch and will be placed in lunar orbit.
The pair will test low frequency radio astronomy and space-based interferometry, as well as carry an amateur radio payload developed by students at the Harbin Institute of Technology (HIT), and a microcameradeveloped by the King Abdulaziz City for Science and Technology (KACST) of Saudi Arabia.
Lander and rover
The lander and rover - repurposed backups to the Chang'e-3 mission - will launch around six months later, in November or December, and attempt the first-ever soft landing on the lunar far side.
The candidate landing sites are within the South Pole–Aitken basin, a huge crater that may include lunar mantle excavated by the impact that formed it and thus offer unique insights into the interior of the Moon, what it is made of and how it formed.
The lander will carry a Landing Camera (LCAM), Terrain Camera (TCAM), a Low Frequency Spectrometer (LFS), and Lunar Lander Neutrons and Dosimetry (LND), with the latter 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, from Sweden, an Advanced Small Analyser for Neutrals (ASAN).
The Chang'e-3 lander on Mare Imbrium, imaged by the Yutu rover.
TCAM and PCAM on Chang'e-3 returned astounding images from Mare Imbrium. The Chang'e-4 landing mission will also include a student outreach-inspired mini ecosystem, including potatoes, arabidopsis seeds and silkworm eggs.
For latest news and developments on the mission, see our features on China's Chang'e-4 mission to the far side of the Moon and China's lunar exploration programme.
A prototype of the mini lunar biosphere experiment for the Chang'e-4 mission, launching in late 2018.
China preparing to launch Chang’e-4 relay satellite May 21
HELSINKI, Finland – China is set to launch a relay satellite to the second Earth-moon Lagrange point May 21, in a necessary precursor to the planned Chang’e-4 soft-landing on the lunar far side late in the year.
Chang’e-4 is the backup to the Chang’e-3 mission which put a lander and rover on Mare Imbrium in late 2013. Following that success, the lunar craft have been repurposed for a pioneering landing on the moon’s far side.
The lunar far side does not face the Earth as the moon’s orbital period matches its rotational period, thus requiring a relay satellite to facilitate communications.
Launch of the satellite will take place at the Xichang Satellite Launch Center in the southwest of the country via a Long March 4C rocket, with the three-day launch window opening on May 21.
The relay satellite, recently named Queqiao – or Magpie Bridge, taken from a Chinese folklore tale that sees two lovers reunited once a year when a flock of magpies form a bridge across the Milky Way — will orbit around the Lagrange point around 65,000 kilometers beyond the moon, so as to be visible to both ground stations on the Earth and the lander and rover on the lunar far side at all times.
Its main function will be to relay telecommands from the ground to the Chang’e-4 lunar spacecraft and transmit data and telemetry back to Earth via S-band, while using x-band to communicate with the lander and rover.
Should launch and commissioning of the relay satellite proceed as planned, the lander and rover will be launched by a Long March 3B from Xichang around six months later, in November or December.
Ian Crawford, professor of planetary science and astrobiology at Birkbeck, University of London, told SpaceNews the mission would be a “tremendous undertaking, as it would be the first time any spacecraft has successfully landed on the far side of the moon.”
The landing is currently expected to target the Von Kármán crater within the South Pole-Aitken Basin, though a decision on the final site has not been announced by Chinese scientists.
The South Pole-Aitken Basin is, Crawford notes, a high priority scientific objective for exploration, potentially offering unique insights into the formation of the moon and history of the solar system.
Astronomy goals
The relay satellite, developed by the China Academy of Space Technology, will also carry the Netherlands-China Low-Frequency Explorer (NCLE), a low-frequency, space-based astronomy pathfinder experiment that will attempt to detect radio signals from the cosmic dark ages, before emission of light by the first stars in the universe.
Radioastronomybelow around 30 MHzcan only be carried outeffectively outside of the Earth’s ionosphere, and the satellite’s position beyond the moon will allow it to take a unique look at this largely unexplored region of the electromagnetic spectrum, with minimal interference from Earth.
Professor Heino Falckeof Radboud Universityin the Netherlands and part of the NCLE team told SpaceNewshe doesn’t want to set the bar too high for this attempt at picking up a cosmic dark ages signal. It could put an upper limit on the signal and is expected to be instructive for future low frequency astronomy space missions.
Along with its main objective, NCLE will also aim to characterize the galactic background and measure emissions from the Sun and Jupiter, as well as measure the wake of the solar wind behind the moon.
Falcke says getting the instrument ready in time and integrated on the spacecraft was a “ride on the edge,” with the call for international participation in Chang’e-4 only coming in 2015, and the Dutch team needing to develop their own antenna from scratch, due to ITAR regulations limiting exports to China.
The antenna is only expected to be deployed for use sometime in 2019, after the main Chang’e-4 mission, with the rover having a designed operation time of three months on the lunar surface.
The May launch will also carry two microsatellites, named Longjiang-1 and 2 and meaning ‘dragon river’, which were developed by the Harbin Institute of Technology (HIT) in north-eastern province of Heilongjiang.
The pair will carry synchronized receivers for low frequency astronomy and very long baseline interferometry experiments and operate in a highly elliptical lunar orbit. They will also be available for amateur radio tests, with one of the two 45-kilogram, 50x50x40-centimeter satellites also set to carry a micro optical camera developed by the King Abdulaziz City for Science and Technology (KACST) of Saudi Arabia.
The launch this month will be China’s fifth lunar mission, following two orbiters, Chang’e-1 and Chang’e-2 in 2007 and 2010 respectively, Chang’e-3 in 2013, and the 2014 Chang’e-5 T1 probe which flew a capsule around the moon and back to test re-entry for a planned lunar sample return. The full sample mission, Chang’e-5, is expected to take place in 2019.
Quelle: SN
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