Advancement in communication satellite technology has made it possible for China's lunar exploration program to probe the far side of the Moon, where the US National Aeronautics and Space Administration's (NASA) Apollo program did not reach, experts told Sputnik.MOSCOW (Pakistan Point News / Sputnik - 19th December, 2018) Advancement in communication satellite technology has made it possible for China's lunar exploration program to probe the far side of the Moon, where the US National Aeronautics and Space Administration's (NASA) Apollo program did not reach, experts told Sputnik.
China's Chang'e-4 probe decelerated and entered the lunar orbit on December 12, completing a vital step on its way to make the first-ever soft landing on the far side of the moon, the China National Space Administration (CNSA) said in a statement.
"Next, the control center will adjust the probe's orbit around the moon and test the communication link between the probe and the relay satellite 'Queqiao,' which is operating in the halo orbit around the second Lagrangian (L2) point of the earth-moon system," the CNSA said in the statement.
If the Chinese lunar probe lands on the far side of the Moon successfully, China will accomplish something that the NASA's Apollo program, which brought the first human to the Moon, was not able to complete. Space scientists suggested that advancement in communication satellite technology has played a key role in allowing China to attempt this breakthrough in lunar exploration.
"During Apollo, we talked about landing on the far side of the Moon, but we needed a communication satellite, but none was available. China has launched a communications satellite to enable far side communications and landing. It is a major step forward in enabling full access to all parts of the Moon," James Head, a professor of geological sciences at Brown University who worked on the Apollo project at NASA and provided training for the Apollo astronauts, told Sputnik.
China launched a relay satellite, known as "Queqiao," in May to facilitate communications between the lunar probe and the mission control center. Due to an effect known as tidal locking, the Moon only shows the same side toward the Earth while its other side, known as the far side, is never visible to humans on Earth.
Other space scientists explained why the relay satellite is critical to the success of Chang'e-4 probe's mission to land on the far side of the Moon.
"Chang'e 4 is a robotic mission controlled from Earth, plus it's due to land on the far side of the moon where we don't have a direct sightline -- because of so-called 'tidal locking,' we only ever see the near side of the moon from Earth, never the far side. On the far side of the moon, any instruments are shielded from the Earth's electromagnetic radiation, including humanity's radio transmissions. Any communications must therefore be relayed via a secondary probe, a relay satellite called Queqiao, which China launched in May of this year," Richard De Grijs, a professor of astrophysics at the Macquarie University in Sydney, Australia, told Sputnik.
The Sydney-based scientist illustrated how the relay satellite can help bridge communications between the lunar probe and the mission control center.
"It [the relay satellite] was sent to the so-called second Lagrange point of the Earth-Moon system, some 65,000 to 85,000 [kilometers] (about 40,000-53,000 miles) beyond the Moon. Lagrange points in system of two orbiting bodies are dynamically stable: an object at a Lagrange point will stay there and not drift away over time. China's mission control in Beijing will send their commands to Queqiao for relaying to Chang'e-4. Given the distances involved, Chang'e-4's response will not be immediate but there will be a delay - and that is of course potentially risky if unforeseen circumstances require a change in landing site, for instance," he said.
The phrase "Queqiao," which literally means "magpie bridge," comes from a Chinese folk tale in which the birds formed a bridge across the galaxy to help reunite two lovers who were forced to be separated and could only meet each other once a year thanks to the bridge.
In addition to testing the radio communications through a relay satellite, the Chang'e-4 probe's landing site could also offer interesting answers about the early history of Earth, Professor De Grijs added.
"Geological and mineralogical studies of the landing site, most likely the South Pole-Aitken Basin (SPA), is of key interest to lunar scientists. They think that the lunar surface at the landing site could be made up of material that originated from the deeper lunar mantle but which was thrust upwards by the most recent major impact, billions of years ago. If the Moon was indeed formed from the same material as the Earth, a common assumption held by many lunar scientists, studying the SPA basin geologically could by extension provide insights into the early Earth," he said.
However, the space scientist noted that only a sample return mission in the future can provide more detailed answers about the Moon.
"One of the most exciting questions scientists would like to be able to answer in relation to the SPA basin, that is, to determine its age and composition of the original materials from the deep lunar mantle, will not be addressed since Chang'e 4 does not have the right equipment on board and the expected landing site is not ideal. This would really require a sample return mission instead of the current mission," he said.
The peak of human exploration of the Moon took place in the early 1970s, when the United States and the USSR were locked in a space race as both nations strived to prove its technological superiority during the height of the Cold War. When US-USSR competition moved to other areas, both nations' lunar exploration projects also came to a halt.
"China doesn't see this as a competition, but its successes may well galvanize other nations to follow in its footsteps. NASA seems poised to go back to the moon; I believe that their earlier drive to send humans to Mars is now on the backburner, so who knows, we may well see increased activity in relation to lunar exploration and, eventually, exploitation," he said.
"I imagine that it would all come down to a cost-benefits analysis: are the costs and dealing with the challenges of keeping people alive sustainably worth the advantages of a low-gravity and airless environment? Will it be viable to extract water from below the surface to sustain the resident population and will it be sufficiently cost effective to extract minerals and other ores we may want or need on Earth or for further exploration of the solar system?" he said.
But professor Head from Brown University argued that bases on the Moon would carry similar scientific value as bases in Antarctica.
"In the same manner as in Antarctica (where I have spent five field seasons), bases on the Moon would be amazingly useful, with scientific expeditions over wide regions of the Moon," he said.