Why Is Korea's First Lunar Probe Launched Toward the Sun? [Reading Science]

Conceptual image of the Korean Pathfinder Lunar Orbiter (KPLO).

[Asia Economy Reporter Kim Bong-su] On August 1 next year, Korea's first lunar exploration orbiter (KPLO) will be launched. The imaginary moonland where 'Okto-kki pounds the mortar and the jar plays' will reveal itself to Koreans. In 2024, the Artemis project, humanity's second moon landing led by the United States, will take place. Although the moon was the subject of exploration competition between the U.S. and the former Soviet Union in the 1950s and 60s, it was merely a means to showcase scientific technology and national power, and was neglected for over 50 years. Why are Korea and other countries around the world striving to return to the moon?

◇ Even without Okto-kki and jars, a second Earth

The moon will be used in the future to mine expensive resources and serve as an advanced base for space tourism and exploration. It will be developed as Earth's 'second home' before Mars. It has been confirmed that the moon is richly endowed with valuable minerals such as platinum, rare earth elements, helium-3, and titanium. Recently, the presence of water, essential for long-term human survival, has also been revealed. NASA confirmed the existence of large amounts of water at the lunar south pole through an experiment in 2009 where a satellite collided with the moon and analyzed the flying sand and rock fragments. In 2017, analysis of India's lunar probe Chandrayaan-1 revealed that significant amounts of water exist in the moon's mantle and surface.

This means humans can build bases on the moon, live there long-term, enjoy tourism, mine resources to send back to Earth, and use it as a forward base to send materials to Mars and other planets. Especially on Earth, escaping gravity consumes a lot of energy, making the construction and launch of large spacecraft costly, but the moon's gravity is only one-sixth of Earth's, making it much more feasible. Shuttle spacecraft could travel back and forth between Earth and the moon, transporting tourists, astronauts, and minerals ? this is no longer just imagination but becoming reality. Perhaps in about 30 years, school trips to the moon could become common. In fact, the U.S. has signed Artemis agreements with over ten countries to build a kind of space station called Lunar Gateway and plans to begin full-scale lunar exploration and development starting with the 2024 moon landing mission. Korea officially joined by agreeing to the Artemis Accords during President Moon Jae-in's visit to the U.S. last May.

◇ Korea, the vanguard of the multinational force

The KPLO launched by Korea marks the beginning of independent lunar development and serves internationally as the 'vanguard' for humanity's second moon landing. It will explore the permanently shadowed regions near the lunar south and north poles to identify suitable landing sites. To this end, KPLO is equipped with a shadow camera (Shadow Cam) made by NASA that can see in dark areas. NASA will also provide deep space communication between KPLO and the Korean ground control station, mission design, and navigation services. Utilizing NASA's accumulated knowledge and expertise, the entire mission from reaching the moon to exploration will be designed together with experts from the Korea Aerospace Research Institute (KARI), who will also receive know-how transfer.

KPLO will perform other missions as well. Using KARI's high-resolution camera, it will photograph major candidate landing sites on the lunar surface and areas where water, helium-3, and other resources may exist to provide preliminary information. The Korea Electronics and Telecommunications Research Institute will test space internet equipment communication technology, and the Korea Astronomy and Space Science Institute will create the first-ever polarization images of the lunar surface using a wide-field polarization camera to produce a titanium distribution map. Kyung Hee University’s magnetometer will measure the magnetic field around and on the moon, and the Korea Institute of Geoscience and Mineral Resources will create elemental maps of the lunar surface and space radiation environment maps using a gamma-ray spectrometer.

◇ Four routes to the moon

Jules Verne, famous for 'Around the World in 80 Days,' imagined lunar travel using a giant cannon in his novel 'From the Earth to the Moon.' The distance from Earth to the moon is about 380,000 km, which is not an easy journey. There are four main routes to travel from Earth to the moon. The fastest route is a direct transfer from Earth to the moon, as imagined by Jules Verne, called the 'direct transfer orbit.' Launching a spacecraft in a parabolic trajectory from Earth can reach the moon in 3 to 6 days. However, escaping Earth's gravity directly requires high speed and consumes enormous fuel for deceleration maneuvers. The mission duration is short, and there are many restrictions such as precise technology, know-how, and launch dates. The U.S. succeeded only after 5 to 6 preliminary experiments, indicating the high difficulty.

The WBS Method Chosen by the Korean Lunar Orbiter.

The second option is the 'detour route.' One method is the phase transition approach, where the spacecraft first orbits Earth elliptically and then joins the moon's orbit, taking about 1 to 2 months. This is the easier path adopted by beginner lunar exploration countries such as Japan, China, and India. Another method is the Weak Stability Boundary (WSB) approach, which launches toward the sun, travels far, then returns to enter the moon's orbit, taking about 80 to 140 days. It goes to the Lagrange point where the sun's and Earth's gravity balance, then returns, consuming less fuel than the phase transition method because it uses the sun's force to change orbit. There is also the spiral transfer method, which starts from a very low orbit and spirals outward to escape Earth and reach the moon. This consumes the least fuel but takes about a year.

KPLO initially chose the phase transition method but switched to the WSB method during the design process. Due to the addition of NASA's shadow camera, the weight increased from 550 kg to 678 kg, making a one-year mission impossible, so a fuel-saving method was adopted. Although Korea has no prior experience, NASA, which 'owes' the shadow camera, has taken the lead in transferring know-how. In 2011, NASA's twin lunar orbiters 'GRAIL' successfully used the WSB method. This time, the mission is upgraded to enter the gravitational equilibrium point between the moon and Earth, move slowly, and then be captured into lunar orbit, saving more fuel.

◇ Chuseok 2023, orbiting around the moon

The lunar exploration orbiter is being successfully manufactured, recently completing the attachment of NASA's shadow camera. Other payloads have also been completed and delivered. After final assembly and testing in early May next year, it will be transported to Cape Canaveral Air Force Station in Florida and launched aboard SpaceX's Falcon 9 rocket between August 1 and September 9. The arrival date in lunar orbit is expected to be after December 16 next year. Unfortunately, Korea's first lunar orbiter will not be orbiting the moon by the full moon of Chuseok next year. The orbiter will perform its mission until December 31, 2023, so it will be remembered whenever the moon is seen throughout that year. Meanwhile, the total budget for the KPLO project is 225.5 billion KRW, with an additional 11.6 billion KRW paid to the launch contractor due to the weight increase.