China Launches Satellite For Moon Mission: What Is ‘Dark Side Of The Moon’?


China launches its relay satellite, named Queqiao or Magpie Bridge, on May 21. It is set to become the first satellite operating from the "dark side of the moon."

The Long March-4C rocket that took off at 5:28 a.m. GMT or 1:28 a.m. EDT has carried the satellite from China's Xichang Satellite Launch Center.

The satellite separated from the rocket at approximately 25 minutes after lift-off. It then entered an Earth-Moon transfer orbit with its point of trajectory closest to Earth (perigee) at 200 kilometers while the point farthest away (apogee) is at about 400,000 kilometers.

Dark Side Of The Moon

While reports referring to China's lunar probe mission used the phrase "dark side of the moon," the more appropriate scientific term would be the "far side of the moon."

NASA explains the "far side of the moon" as simply the portion of the moon that always faces away from the Earth. This is because of the phenomenon called "tidal locking" where the moon turns around in its axis at the same speed as it rotates around Earth.

The moon does not emit its own light and instead, reflects the sun's rays. Hence, half of the moon's surface is always illuminated while the other portion is always left unlit.

Since the moon and Earth are moving at the same speed, the darkened portion of the moon seemingly always faces the Earth but this is not the case. In fact, the "far side" also follows the moon phases that people see on Earth except that the phases happened at exact opposite to what the people experienced. When it is a full moon on Earth, it is a new moon in the "far side" and vice versa.

For China, nevertheless, the figurative term "dark side of the moon" was meant to describe the mystery that has yet to be deciphered about the "far side of the moon."

Queqiao Or Magpie Bridge

The satellite weighs about 400 kilograms and is designed to thrive in space for the next three years.

Chen Lan, chief engineer of the Xi'an Branch of the China Academy of Space technology said the Queqiao is carrying several antennas, including an umbrella-shaped one, which could be the largest communication antenna ever used in deep space exploration.

More importantly, the Queqiao carries two microsatellites, the Longjiang-1 and Longjiang-2. These microsatellites are intended to help astronomers understand the cosmic dawn or that point after the Big Bang when the first stars and galaxies were born.

"Exploring the cosmic dawn is our long-term goal," said Chen Xuelei, a cosmologist with the National Astronomical Observatories and the leader of a team tasked to analyze the data acquired by Longjiang-1 and Longjiang-2.

Zhang Lihua, manager of the relay satellite project, highlighted that the launch on Monday is one major step toward the country's ambition of being the first in the world to explore the mysterious region of the moon.

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