South Korea went to the moon on Thursday. But it won’t stop there.
“We are also considering using the moon as an outpost for space exploration,” Kwon Hyun-joon, director general of space and nuclear energy at South Korea’s Ministry of Science, said in a written response to questions. “While we hope to explore the Moon itself, we also recognize its potential to serve as a base for further exploration of deep space such as Mars and beyond.”
South Korea’s lunar probe, called Danuri, was launched on a SpaceX Falcon 9 rocket from Florida, embarking on a circuitous but fuel-efficient trajectory that will see it arrive on the moon in mid-December. There it will begin an orbit at an altitude of 62 miles above the lunar surface. The main assignment is planned to last one year.
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Originally known as the Korea Pathfinder Lunar Orbiter, the mission was named Danuri after it was the winning entry in a naming contest. It is a portmanteau of the Korean words for “moon” and “enjoy.”
Danuri will join spacecraft from NASA, India and China currently exploring Earth’s companion. Just like the United Arab Emirates, which was launched to Mars on a Japanese rocket in 2020, South Korea is the latest country with a small but ambitious space program to embark on an extra-low Earth orbit. And like the UAE’s Hope orbiter, the Danuri mission is intended to make meaningful scientific contributions to the global effort to explore and understand the solar system.
Kwon said the main goal of the Danuri mission was to develop basic technologies such as orbital path design, deep space navigation, a high-power propulsion system and a 35-meter antenna to communicate with distant spacecraft.
But the spacecraft’s scientific payload is sophisticated and will help scientists in South Korea and globally study the moon’s magnetic field, measure the abundance of elements and molecules such as uranium, water and helium-3 and photograph the dark craters at the lunar poles, where the sun never shines. In addition to providing one of the instruments, called ShadowCam, NASA selected nine scientists to participate in Danuri.
One of its most important scientific instruments is a magnetometer. The Moon’s interior no longer generates a magnetic field, but it once did, and that primordial field is preserved in lava flows that solidified during this epoch.
Ian Garrick-Bethell, a professor of planetary science at the University of California, Santa Cruz and a participating scientist on the Danuri mission, said the early magnetic field appears to have been surprisingly strong — potentially even as much as twice Earth’s strength. current magnetic field.
Garrick-Bethell said it was puzzling that “such a tiny little iron core could have generated such a strong magnetic field.”
He hopes that after the spacecraft’s primary one-year mission is complete, South Korea may choose to move Danuri much closer to the moon’s surface, within 12 miles or less, where the magnetometer can get a much better look at the magnetized rocks.
“Even a few passes at the low altitudes can help limit how strongly magnetized the rocks are,” he said.
Garrick-Bethell is also looking to use the magnetometer to study magnetic fields generated in the moon when it is buffeted by the solar wind, a stream of charged particles coming from the sun.
The rise and fall in the strength of the magnetic field in the solar wind induces electric currents in the moon, and the electric currents in turn generate magnetic fields that will be measured by Danuri. The properties of the magnetic field will provide hints about the structure and composition of the moon’s interior.
This work also requires combining measurements with those made by two NASA spacecraft, THEMIS-ARTEMIS P1 and P2, which travel around the Moon in highly elliptical orbits, so that they can measure the changes in the solar wind while Danuri measures the induced magnetic fields closer to the surface .
“What we would learn from that is a kind of global map of the interior temperature and potential composition and maybe even the water content of the deep parts of the moon,” Garrick-Bethel said.
Scientists will use another of Danuri’s instruments, a gamma-ray spectrometer, to measure amounts of different elements on the moon’s surface. Danuri’s device can pick up a wider range of lower-energy gamma rays than similar instruments on previous lunar missions, “and this area is full of new information for discovering elements on the moon,” said Naoyuki Yamashita, a New Mexico-based researcher who works for Planetary Science Institute in Arizona. He is also a participating scientist at Danuri.
Yamashita is interested in radon, which is formed by the breakdown of uranium. Because radon is a gas, it can travel from the interior of the moon to the surface. (This is the same process that sometimes causes the build-up of radon, which is also radioactive, in the basements of houses.)
The amounts of the radioactive elements can provide a history that explains when different parts of the moon’s surface cooled and hardened, Yamashita said, helping scientists determine which of the moon’s lava flows are older or younger.
The Korean Aerospace Research Institute, South Korea’s equivalent of NASA, will use Danuri’s high-resolution camera to scout the lunar surface for potential sites for a robotic lander mission in 2031, Kwon said.
A second camera will measure polarized sunlight bouncing off the moon’s surface, revealing details about the size of particles that make up the lunar soil. Because the constant bombardment of solar wind, radiation, and micrometeorites breaks the Earth apart, the size of grains found in a crater can provide an estimate of its age. (Smaller grains indicate an older crater.)
The polarized light data will also be used to map the abundance of titanium on the moon, which may one day be mined for use on Earth.
NASA provided one of the cameras, a ShadowCam, which is sensitive enough to pick up the few photons that bounce off the terrain into the moon’s dark, permanently shadowed craters.
Located at the lunar poles, these craters remain eternally cold, below minus 300 degrees Fahrenheit, and contain water ice that has accumulated over the eons.
The ice can provide a frozen history of the 4.5 billion year old solar system. It could also be a wealth of resources for future visiting astronauts. Machines on the moon could extract and melt the ice to provide water. This water can then be broken apart into oxygen and hydrogen, which would provide both air for astronauts to breathe and rocket propellants for travelers wishing to travel from the moon to other destinations.
One of the main purposes of ShadowCam is to find the ice. But even with Danuri’s sophisticated instruments, it can be challenging. Shuai Li, a researcher at the University of Hawaii and a Danuri participating scientist, believes the concentrations may be so low that they would not be noticeably brighter than areas that do not contain ice.
“If you don’t look closely at it, you might not be able to see it,” Li said.
Jean-Pierre Williams, a planetary scientist at the University of California, Los Angeles, and another participating scientist on the Danuri mission, hopes to produce detailed temperature maps of the craters by combining the ShadowCam images with data collected by NASA’s Lunar Reconnaissance Orbiter.
NASA’s orbiter, which has been studying the moon since 2009, has an instrument that records the temperature on the moon’s surface. But these measurements are blurry over a fairly large area, about 900 feet across. The resolution of a ShadowCam is approximately 5 feet per pixel. Thus, the ShadowCam images used together with computer models can make it possible to test temperature variations on the surface.
“With this data, we can map local and seasonal temperatures,” Williams said. That in turn could help scientists understand the stability of water and carbon dioxide ice in the crater.
Scientists must wait several months before the science begins. The spacecraft takes a long, energy-efficient route to the moon. It first goes towards the Sun, then goes around to be caught in lunar orbit on December 16. This “ballistic trajectory” takes longer, but does not require a large engine to be fired to slow the spacecraft as it reaches the moon.
South Korea has an extensive military missile program and has placed several communications and Earth observation satellites in low Earth orbit since the launch of the first in 1992. And the country has expanded its domestic rocket launch capabilities so that future missions may not need to rely on SpaceX, or on other countries, to get to space. In June, the Korean Aerospace Research Institute placed several satellites into orbit with the second flight of Nuri, its homegrown rocket.
“We will take on challenging projects such as lunar landers and asteroid exploration,” Kwon said.
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