China launches relay satellite to explore Moon's far side

A Long March-4C rocket carrying a relay satellite, named Queqiao (Magpie Bridge), is launched at 5:28 a.m. Beijing Time from southwest China's Xichang Satellite Launch Center, May 21, 2018. China launched a relay satellite early Monday to set up a communication link between Earth and the planned Chang'e-4 lunar probe that will explore the mysterious far side of Moon, which can not be seen from Earth.Photo:Xinhua

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China launched a relay satellite early Monday to set up a communication link between Earth and the planned Chang'e-4 lunar probe that will explore the Moon's mysterious far side.

The satellite was carried by a Long March-4C rocket that blasted off at 5:28 a.m. from southwest China's Xichang Satellite Launch Center, according to the China National Space Administration (CNSA).

The satellite was named Queqiao, or Magpie Bridge. In a Chinese folktale, magpies form a bridge on the seventh night of the seventh month of the lunar calendar to enable Zhi Nyu, a weavergirl who is the seventh daughter of the Goddess of Heaven, to meet her beloved husband, cowherd Niu Lang, for one day. The couple were banished to opposite sides of the Milky Way as their love was not allowed.

"The launch is a key step for China to realize its goal of being the first country to send a probe to soft-land on and rove the far side of the Moon," said Zhang Lihua, manager of the relay satellite project.

About 25 minutes after lift-off, the satellite separated from the rocket and entered an Earth-Moon transfer orbit with the perigee at 200 km and the apogee at about 400,000 km. Meanwhile, the solar panels and the communication antennas were unfolded.

Queqiao is expected to enter a halo orbit around the second Lagrangian (L2) point of the Earth-Moon system, about 455,000 km from the Earth. It will be the world's first communication satellite operating in that orbit.

But the mission must overcome many challenges, including multiple adjustments to its orbit and braking near the Moon and taking advantage of the lunar gravity, Zhang said.

Chinese scientists and engineers hope the Queqiao satellite will form a communication bridge between controllers on Earth and the far side of the Moon where the Chang'e-4 lunar probe is expected to touch down later this year.

Monday's launch was the 275th mission of the Long March rocket series.

Tidal forces of the Earth have slowed the Moon's rotation to the point where the same side always faces the Earth, a phenomenon called tidal locking. The other face, most of which is never visible from Earth, is the far side or dark side of the Moon, not because it's dark, but because most of it remains unknown.

With its special environment and complex geological history, the far side is a hot spot for scientific and space exploration. The Aitken Basin of the lunar south pole region on the far side has been chosen as the landing site for Chang'e-4. The region is believed to have great research potential.

However, landing and roving require a relay satellite to transmit signals. The Chang'e-4 mission will be more complicated than Chang'e-3, China's first soft landing on the Moon in 2013.

"We designed an orbit around the Earth-Moon L2 point where 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.

Establishing a communication link is essential for the success of the Chang'e-4 mission, said Bao.

The satellite, weighing about 400 kg and with a designed life of three years, carries several antennas. One, shaped like an umbrella with a diameter of 5 meters, is the largest communication antenna ever used in deep space exploration, said Chen Lan, deputy chief engineer of the Xi'an Branch of the China Academy of Space Technology (CAST).

The satellite could stay in the halo orbit around the L2 point of the Earth-Moon system for a long time by using relatively little fuel, thanks to the gravitational equilibrium at that point.

Together with Queqiao, two microsatellites, Longjiang-1 and Longjiang-2, were launched to orbit the Moon to conduct ultra-long-wave astronomical observation, which could help scientists study the cosmic dawn.

Astronomers yearn for a completely quiet electromagnetic environment to detect the weak signals emitted from remote celestial bodies in deep space.

The far side of the Moon is such a place, as the body of the Moon shields against radio interference from the Earth. From there, astronomers can study the origins and evolution of stars and galaxies, peering into the dawn of the universe.

"Exploring the cosmic dawn is our long-term goal, and Longjiang-1 and Longjiang-2 are a preliminary experiment that could lay the foundation for future exploration," said Chen Xuelei, a cosmologist with the National Astronomical Observatories, who leads a team to analyze the data of the microsatellites.

The relay satellite is also equipped with a low-frequency radio spectrometer developed by Dutch scientists, which will help scientists "listen" to the deeper reaches of the cosmos.

A small lunar optical imaging detector developed by Saudi Arabia is installed on the satellite.

China's lunar exploration program will be a new research platform for scientists around the world. The lander and rover of Chang'e-4 will be equipped with instruments developed by Germany and Sweden, said Sun Zezhou, chief designer of the Chang'e-4 mission.

In addition, the satellite carries a reflector developed by the Sun Yat-sen University to conduct laser-ranging experiments between the relay satellite and an observatory on the ground at a maximum distance of 460,000 km. If successful, it will set a new record for this kind of experiment, said Zhang Lihua.

To raise interests of the public in space exploration, the Lunar Exploration and Space Program Center of the CNSA has invited people to write down their hopes for lunar and space exploration, and the relay satellite is carrying the names of about 100,000 participants and their hopes into deep space.

Quelle: globaltimes

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China launches relay satellite for far side moon landing

BEIJING (AP) — China has launched a relay satellite as part of a groundbreaking program to land a probe on the far side of the moon this year.

The China National Space Administration said on its website that the satellite lofted into space early Monday aboard a Long March-4C rocket will facilitate communication between controllers on Earth and the Chang'e 4 mission.

China hopes to become the first country to soft-land a probe on the moon's far side, also known as the dark side because it faces away from Earth and is comparatively unknown.

China previously landed its Jade Rabbit rover on the moon and plans to land its Chang'e 5 probe there next year and have it return to Earth with samples — the first time that has been done since 1976.

Quelle: Houston Chronicl

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China launches Queqiao relay satellite to support Chang'e-4 lunar far side landing mission

A Long March 4C rocket lifts off from LC9 at Taiyuan Satellite Launch Centre at 18:35 UTC November 14, 2017, carrying the Fengyun-3D weather satellite and HEAD-1 microsatellite. Xinhua

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China has successfully launched a lunar communications relay satellite designed to support an unprecedented mission to put a lander and rover on the far side of the Moon in late 2018, as well as carry out pioneering astronomy.

The Chang’e-4 relay satellite, accompanied by two microsatellites, lifted off atop a Long March 4C rocket from the Xichang Satellite Launch Centre at 21:28 UTC on Sunday (05:28 Beijing time, May 21).

The spacecraft was successfully inserted into a lunar transfer orbit and separated from the rocket’s upper stage, the China Aerospace Science and Technology Corporation (CASC) – the main contractor for the space programme – confirmed just under an hour after launch.

Named ‘Queqiao’ – referencing a ‘Magpie Bridge’ from a Chinese folklore of lovers crossing the Milky Way – the relay satellite is now on an 8-to-9 day journey to the second Earth-Moon Lagrange point (E-M L2) some 60-80,000 kilometres beyond the Moon and nearly half a million kilometres from Earth.

The main aim of the mission is to provide a means of communications for setting down and operating a lunar lander and rover on the far side of the Moon, a feat that has never been attempted.

As the Moon is ‘tidally locked’, taking the same time to go around the Earth as it does to rotate once, the lunar far side never faces the Earth. The landing mission thus requires a communications relay satellite with simultaneous line-of-sight to both the lander and rover on the Moon and terrestrial ground stations.

The gravitationally stable E-M L2 will allow for a stable orbit from which the satellite can perform this task.

Queqiao will make a lunar swing-by to send it towards its intended destination beyond the Moon and use its own propulsion to enter a halo orbit around the Lagrange point.

Once in place the 448 kg CAST100 satellite, developed by the China Academy of Space Technology (CAST), a spacecraft maker under CASC, will undergo testing of its 4.2m parabolic antenna and functions ahead of the landing mission which will take place in around six months.

The relay satellite marks China’s fifth lunar mission, following two orbiters, Chang'e-1 in 2007 and Chang’e-2 in 2010), the 2013 Chang'e-3 lander and rover, and a 2014 test lunar return mission.

In 2019 China will launch the Chang’e-5 mission to collect 2 kg of samples from the Moon and bring them to Earth.

Today’s launch was China’s 15^th of the year, with the country aiming for a national record of around 40 in 2018.

Pioneering astronomy

Following the landing mission, the relay satellite will deploy three 5-metre monopole antennas which will be used for very low frequency astronomy that is not possible on Earth due to the planet’s atmosphere.

The Netherlands-China Low-Frequency Explorer (NCLE), developed by Radboud University and others, will attempt to detect a low frequency signalfrom the ‘dark ages’ of the universe, a few hundred million years after the Big Bang and before the first stars begin to shine.

Other objectives, says Marc Klein Wolt of Radboud University and NCLE project leader, include surveying the solar system at these frequencies, and act as a pathfinder for future missions.

Asked if NCLE could also - despite not being a science objective for the team - contribute to the search for extraterrestrial intelligence (SETI), Klein Wolt says that, "In principle it could, as we are opening a new window on the universe, but I'm not expecting to find ET."

Two microsatellites, Longjiang-1 and -2 (River Dragon-1 and -2), were also aboard the launch and will enter highly elliptical lunar orbits to perform their astronomy tasks.

The 45-kg, 50x50x40-cm satellites developed by the Harbin Institute of Technology (HIT) in Heilongjiang Province will use 1-metre antennas to test low frequency radio astronomy and space-based interferometry.

Mainly a technical verification for future missions, the pair will also carry out amateur radio experiments, with one will also carrying a small optical camera developed by Saudi Arabia.

Landing mission in late 2018

Chang’e-4 was originally a backup for the Chang’e-3 mission that saw a lander and the Yutu (Jade Rabbit) rover touch down on Mare Imbrium in 2013.

As that mission was successful – despite a mechanical failure afflicting Yutu – the Chang’e-4 spacecraft have been repurposed for an ambitious lunar far side landing.

The target for the landing is expected to be within the Von Kármán impact crater within the South Pole-Aitken Basin, a scientifically intriguing area that could offer tremendous insights into the history and development of both the Moon and the solar system.

Cameras on Chang'e-3 returned astounding images from Mare Imbrium, and the same is hoped for Chang'e-4. Chang'e-3 made a number of discoveries with its instruments, including multiple distinct layers beneath the surface, suggesting the Moon has a more complex geological history than previously thought.