[Yang Nak-gyu's Defense Club] How Many Satellites Have Become Space Debris?

[Asia Economy Reporter Yang Nak-gyu] Interest in 'Space Junk' is increasing as a satellite launched by Iran failed to enter orbit. When a satellite is not properly launched or reaches the end of its lifespan, it becomes space junk. It also becomes space junk if it is shot down. If this space junk falls to Earth, it can lead to fatal accidents.

On the 9th (local time), Iran launched the satellite 'Zafar' from the Imam Khomeini National Space Center in Semnan Province, about 230 km southeast of the capital Tehran, but it could not reach the target orbit due to low speed, according to Iranian state TV. According to Iranian media, the Zafar satellite is an environmental research satellite developed by the Science and Technology Research Institute of Tehran University. It weighs 90 kg and can investigate petroleum resources, minerals, and natural disasters.

There are many such failed satellites, i.e., space junk. The official term for space junk is Orbital Debris. The U.S. Joint Space Operations Center (JSpOC) is closely monitoring not only about 400 publicly known satellites but also an estimated 800 military satellites unofficially launched by various countries. Because of this, collisions involving military satellites are increasing the amount of space junk. The number of space junk pieces is estimated to exceed about 20,000.

The types and sizes of space junk drifting in space vary. They range from tiny metal particles as small as dust to spacecraft parts weighing hundreds of kilograms. It is known that there are about 19,000 pieces larger than 10 cm, 500,000 pieces between 1 and 10 cm, and tens of millions smaller than 1 cm. Most space junk floats at altitudes between 800 and 1,500 km above the Earth. Debris discarded below 600 km usually burns up in the Earth's atmosphere within a few years. However, debris at altitudes above 800 km can drift in space for decades to centuries.

This space junk is a deadly threat to satellites operating in space. The debris orbiting in space travels at speeds of up to 28,000 km/h (about 8 km/s), so collisions cause major accidents. Even debris the size of a grain of sand carries kinetic energy comparable to a bowling ball flying at 160 km/h.

In fact, the uncontrolled Chinese space station 'Tiangong 1' fell into the middle of the South Pacific Ocean. Tiangong 1, China's first experimental space station, was launched in September 2011 but lost control due to an unknown malfunction in March 2016, less than five years later. When the fall zone included South Korea, tension rose as the reentry time approached. The satellite fell into the South Pacific area without causing significant damage, but China suffered global embarrassment.

Countries are developing technologies to monitor and intercept space junk because the damage from a fall can be severe. In July 2002, Russia completed the Okno optical space surveillance facility at an altitude of 2,200 meters in Tajikistan. This facility monitors satellites and space debris at altitudes of 40,000 km. Last year, the U.S. deployed a long-range early warning radar capable of detecting about 500 targets within 6,000 km altitude for missile defense.

China has operated space surveillance and tracking stations using optical, radar, and laser equipment through facilities located in Shanghai and Beijing since the 1970s. China operates a Satellite Laser Ranging (SLR) station using lasers developed in the early 1980s. At that time, the orbit estimation accuracy was about 1 to 2 meters for low Earth orbit satellites. Currently, China has additionally established a 1.56-meter optical telescope and a 60 cm laser satellite tracking system to monitor satellites day and night.

Last year, the United States officially launched the U.S. Space Command under the Department of Defense. Led by Commander Jay Raymond, the Space Command is the 11th unified combatant command under the Department of Defense. It is tasked with defending the U.S. and its allies from threats in space and preventing collisions through missile warning, satellite operations, and space control. President Trump signed an executive order in December 2018 to establish the Space Command.