[Reading Science] Large Satellite Crash... Why China Gets Criticized but the US Does Not?

Space Debris Q&A

At the end of last August, debris from the upper part of the Changzheng 5B rocket, used for constructing the Chinese space station, fell over Malaysia and Singapore. Photo by Twitter

[Asia Economy Reporter Kim Bong-su] On the 9th, the US Earth Radiation Budget Satellite (ERBS) re-entered and fell through the atmosphere, raising awareness about the space debris problem. Although the ERBS satellite crashed into the sea near the Bering Sea without causing damage, the growing issue of space debris is raising concerns not only about damage caused by debris falling to the Earth's surface but also about hindering humanity's advancement into outer space.

How serious is the space debris problem?

Humanity is at risk of being trapped on Earth due to space debris. This is the background behind the term 'Kessler Syndrome.' It was proposed by Donald Kessler, a NASA scientist, in a 1978 paper. He warned that exponentially increasing space debris caused by satellite collisions, malfunctions, and space warfare could surround Earth, making orbital activities and outer space exploration impossible.

The problem is that these concerns are not just 'groundless fears' but are becoming a reality. The European Space Agency (ESA) estimates that there are over 36,500 pieces of space debris larger than 10 cm, over 1 million pieces between 1 and 10 cm, and about 330 million pieces between 1 cm and 1 mm orbiting Earth. Since 2020, the situation has worsened due to the surge in launches of small satellites and satellite destruction tests by some countries. Space debris orbits Earth at an incredible speed of over 7 km/s. Even small debris can cause significant damage to satellites. Occasionally, large debris falls to the surface, becoming a source of fear. Aside from the recent US large satellite crash, the most recent case was the fall of the upper stage of China's Changzheng 5B rocket weighing over 20 tons on November 4 last year. The crashes of China's Tiangong 1 in 2018 and the former Soviet Union's nuclear satellite Cosmos 954 in 1978 also caused global fear. Astronomers complain that space debris twinkles like stars, making observations difficult.

In response, major countries such as the US and Europe have established regulatory measures, including mandatory atmospheric re-entry and incineration at the end of satellite lifespans and the use of materials that burn easily. Research and development are also underway on special coatings and materials to facilitate astronomical observations. In November 2021, the US condemned Russia's satellite destruction test and has been promoting an international agreement to ban similar tests since last year to prevent recurrence.

Why was it so controversial this time?

As of 2020, more than 3,000 satellites have been launched worldwide. Since then, companies like SpaceX have launched large numbers of small satellites for space internet. Therefore, it has become common for space launch vehicle debris or malfunctioning/end-of-life satellites to fall to the Earth's surface. Satellites and space debris usually orbit at speeds around 7 km/s but are gradually pulled in by Earth's gravity and atmospheric friction, re-entering the atmosphere and falling to the surface. Small debris is completely incinerated by atmospheric friction heat and disappears like meteors. However, occasionally, large space debris can have fragments that reach the surface. The US ERBS satellite was a large object weighing nearly 2.5 tons, raising concerns that fragments could reach the surface, which made it an issue. Additionally, the ERBS satellite, launched in 1984, helped humanity by confirming that the ozone layer was disappearing on a large scale through Earth’s thermal radiation distribution surveys, adding historical significance.

[Image source=Yonhap News]

Why is China criticized but the US is not?

China does not provide timely and accurate information about the fall of its space objects. Last November, China launched the Changzheng 5B rocket to place the Tiangong space station module into orbit. Unlike other rockets, the upper stage of the Changzheng 5B rocket did not fall after stage separation but remained in orbit for about a week before falling. However, the Chinese government did not properly share trajectory tracking information with the world. In contrast, the US government shares space object fall information almost in real-time with countries worldwide through NASA, the North American Aerospace Defense Command (NORAD), and the Space Force, issuing warnings.

How do we prepare?

Currently, South Korea is preparing for space debris falls according to the Basic Plan for Space Risk Preparedness established in 2013. The Korea Astronomy and Space Science Institute (KASI) has been designated as the space risk monitoring agency and uses its own space object electronic-optical monitoring system (OWL-NET) to monitor whether space objects fall on or near the Korean Peninsula. The observatories, located in South Korea, the US, Israel, Morocco, and Mongolia, are equipped with 50 cm wide-field telescopes, CCD cameras, and high-speed satellite tracking mounts. The Air Force also introduced an electronic-optical satellite monitoring system early last year and has deployed it operationally. KASI monitors when and where satellites might fall by combining information collected via OWL-NET and the US-provided Space Track system. They have developed and use the 'Cassiopeia (KASI's Orbit Prediction & Estimation, Integrated Analysis System)' applying satellite flight dynamics technology. If a threatening satellite or space debris fall is expected, they predict and analyze the fall time and location using their own orbital analysis algorithms and report to the Ministry of Science and ICT.

The Ministry of Science and ICT, the main government agency responsible for space debris falls, responds based on this information according to the Artificial Space Object Fall Preparedness Manual. If there is a possibility of debris falling from large space debris, a caution alert is issued, and if it is expected to pass through the Korean Peninsula, a warning alert is issued. When a warning alert is issued, a Space Risk Countermeasure Headquarters is formed, led by the first vice minister and involving officials from various ministries. Participants include the Ministry of Land, Infrastructure and Transport, Ministry of National Defense, Ministry of the Interior and Safety, Ministry of Foreign Affairs, Korea Meteorological Administration, Ministry of Oceans and Fisheries, Ministry of Environment, Korea Coast Guard, Korea Forest Service, Nuclear Safety and Security Commission, and National Fire Agency. This headquarters discusses and implements safety measures for each ministry's responsibilities, such as issuing aviation operation advisories like on the 9th. Disaster safety messages are sent, and broadcasts urge citizens to refrain from going out and to exercise safety precautions. If a fall or damage on the Korean Peninsula is confirmed, the alert level is raised to 'serious.' At this stage, a Central Accident Response Headquarters is formed and operated, and if the situation is severe, it expands to the Central Disaster Countermeasure Headquarters to handle damage recovery and restoration.

Bohyeonsan Observatory Telescope

What about damage compensation?

If a Korean satellite falls and causes damage to Koreans, compensation is possible. Even if the satellite or space object belongs to a foreign country, compensation can be claimed if nationality is confirmed. According to the Ministry of Science and ICT, the United Nations (UN) signed the Outer Space Treaty in 1967 with participation from 107 countries. This treaty includes the 'Convention on International Liability for Damage Caused by Space Objects,' which holds the launching country liable for damages caused by rocket or satellite debris to other countries. For example, when the former Soviet Union's nuclear satellite Cosmos 954 crashed in Canada in 1978, radioactive debris scattered over an area of 20 km², causing damage. The Soviet Union eventually paid 3 million Canadian dollars in compensation.

Nuriho Performance Verification Satellite Observed by OWL-Net

South Korea is also a space debris emitter

South Korea is also a 'space debris emitter' as it has entered space development with satellite launches and the successful second launch of the Nuri rocket last year. Of the 17 satellites launched so far, 9 have become space debris drifting in orbit after mission completion. These include multipurpose practical satellites 1 and 2, Our Star 1 to 3, Science and Technology Satellites 1 to 3, and the Naro Science Satellite. Additionally, space debris was generated during the first and second Nuri rocket launches. After the first launch in October 2021, the third stage and dummy satellites are still orbiting, and after the second launch in June last year, the third stage, performance verification satellite, and CubeSat are in orbit. The performance verification satellite is expected to have a lifespan of two years, after which it will become space debris. The Danuri lunar orbiter, launched in August last year, has a mission lifespan of one year after entering lunar orbit but is expected to operate for 2 to 3 years or more due to fuel savings. The Korea Aerospace Research Institute (KARI) plans to decide its 'trajectory' after the mission ends, either by crashing onto the lunar surface for scientific experiments or moving to a satellite graveyard orbit.