Scientists Who Risked Their Lives on a 128kg Diet... The Story of the Lunar Orbiter [Reading Science]

[Asia Economy Reporter Kim Bong-su] South Korea's first space exploration plan, the lunar exploration orbiter launch operation, is progressing smoothly. The Ministry of Science and ICT announced on the 1st that the development of the payload and the main body is almost complete, and there is no obstacle to the launch of the lunar exploration orbiter in August 2022. At the same time, they revealed the specific mission of the lunar exploration orbiter. For the first time in human history, it will capture polarized images to analyze the patterns and causes of changes on the lunar surface. In addition, the ShadowCam, carried by NASA, will serve as the vanguard for Artemis, humanity's second lunar landing project scheduled for 2024. NASA plans to use this camera to photograph the permanently shadowed regions of the lunar poles, which were previously impossible to capture, to select landing sites for the Artemis project.

Although the project is progressing rapidly as if catching a favorable wind, the lunar exploration plan, which began in 2007, has experienced numerous twists and turns over more than a decade. It has faced all kinds of difficulties, including political turbulence, technical challenges, cooperation issues with foreign agencies, and internal conflicts.

The first obstacle the lunar exploration project encountered was political turbulence. Originally, South Korea's independent lunar exploration plan was established during the Roh Moo-hyun administration in 2007. At that time, based on the opinions of experts from the Korea Aerospace Research Institute and others, it was a long-term project aiming to launch a lunar exploration orbiter in 2020 and a lunar lander in 2025. The schedule considered the domestic technology, manpower level, and budget. However, when the Park Geun-hye administration took office in 2013, these plans were accelerated by 3 to 5 years. The launch of the lunar orbiter was moved to 2017, and the lunar lander to 2020. This was a measure following President Park Geun-hye's election pledge.

High-resolution camera to be mounted on lunar exploration orbiter

This plan met with strong opposition from field researchers and technicians. They argued it was an unreasonable plan that could not meet the timetable. Eventually, due to technical issues, the lunar exploration schedule was postponed repeatedly. Under the Moon Jae-in administration, the lunar orbiter launch was extended to December 2020, and the lunar lander launch was extended to within 2030. After another extension, the current schedule was finalized: the lunar orbiter launch in 2022 and the lunar lander launch within 2030.

The second obstacle was a technical challenge: the 'weight' issue. Initially, the lunar exploration orbiter was planned to be launched into space aboard the Korean launch vehicle 'Nuriho,' which was being developed around the same time. The problem was that Nuriho's maximum payload capacity was only 1.5 tons. Therefore, the research team tried to reduce the lunar orbiter's weight to within 550 kg. They even offered rewards to encourage weight reduction efforts, but ultimately faced technical limits and failed. Currently, the lunar orbiter's weight is fixed at 678 kg, which is 128 kg heavier than the target.

Magnetometer to be installed on lunar exploration orbiter

As the orbiter's weight increased, the entire lunar exploration project was adjusted in September 2019. The launch vehicle was changed from Nuriho to SpaceX's Falcon 9, a U.S. private space company. With the increased budget to pay SpaceX, the total cost rose by more than 20 billion KRW from the original 197.8 billion KRW.

The increase in payload weight caused another serious problem. The fuel consumption increased, which affected the orbiter's lifespan. Consequently, scientists at KARI revised their initial goal of maintaining a 100 km circular orbit for one year. The new plan was to operate in an elliptical orbit for nine months, flying between 100 km and 300 km above the Moon when closer or farther, and only operate in a 100 km circular orbit for the last three months. This was a desperate measure to meet the original one-year operation period.

However, this plan change faced another barrier: NASA protested. NASA insisted that to capture images of the polar regions as originally intended, a circular orbit was necessary, and three months would not provide sufficient data. They demanded the original one-year circular orbit operation be maintained.

Wide-field polarization camera to be mounted on the lunar exploration orbiter.

Eventually, after much debate, KARI and NASA agreed to modify the lunar orbiter's orbit insertion method to minimize fuel consumption and achieve the goal of one-year circular orbit operation. Specifically, the Korean researchers had chosen the previously used Phasing Loop method, where the satellite orbits Earth several times in a long elliptical orbit before entering the lunar orbit. This method takes about a month and has been successfully used by Japan and India.

However, NASA proposed switching to the Weak Stability Boundary (WSB) method. This method uses the gravitational fields of the Earth, Moon, and Sun to approach the lunar orbit. Although it takes longer, it minimizes fuel consumption. However, despite the recent success of the U.S. lunar gravity exploration mission GRAIL, this method is not yet fully verified and carries some risk. Nevertheless, the scientists from both countries agreed last year to implement the WSB method, with the premise that the U.S. would transfer their successful know-how to South Korea as much as possible.

Space internet test equipment to be installed on the lunar exploration orbiter.

The development of the lunar exploration orbiter has also faced numerous internal conflicts. A representative incident occurred when the government withheld incentives totaling 103 million KRW, which were supposed to be paid to lunar exploration project researchers between January and May 2019, after KARI failed to reduce the orbiter's weight. KARI researchers claimed these were routine research allowances that should have been paid and filed a wage arrears lawsuit early last year, which is currently ongoing.

The government, on the other hand, argued that since the lunar exploration project was delayed at that time, and there was no research activity during that period, they could not pay the personnel expenses. Although KARI paid wages during that period on its own, the incentive issue remained unresolved and became a source of conflict. There were also ongoing disputes between the responsible Ministry of Science and ICT and KARI, the practical executing agency. Recently, former KARI President Lim Cheol-ho, who completed a three-year term, was abruptly dismissed by the Ministry of Science and ICT at the end of last year.

Shading camera for lunar exploration orbiter developed by NASA, USA.

In any case, South Korea's independent lunar exploration orbiter launch is being prepared smoothly and is expected to be possible in August next year. The lunar exploration project, which has gone through many trials and tribulations, will enhance South Korea's international standing and boost national pride. It will also directly contribute to national interests through future full-scale space development, resource acquisition via asteroid and Mars exploration, and security assurance. We hope that the lunar exploration orbiter, which has endured many hardships, will sail smoothly from now on.