Satellites & Light Pollution: Impact on Astronomy

Active international discussions on ‘protection of astronomical observations’
Emitting radio waves while traveling through low Earth orbit… Increased ‘noise’ affects observations
A night-time solar power generation experiment also appeared… Brighter than the full moon in certain areas
Cooperation, including sharing of operational information, is necessary.

The night sky, a source of space exploration and scientific curiosity, is gradually disappearing. Thousands of artificial satellites are orbiting the Earth, spreading radio waves, and plans have even emerged to utilize sunlight even at night. The astronomy community is raising its voice of warning, saying that the sky is no longer dark and quiet.

● Electromagnetic waves from tens of thousands of satellites interfere with astronomical observations

Currently, about 12,000 satellites, including SpaceX’s ‘Starlink’, are operating in low Earth orbit (LEO). Moreover, the number of satellites is expected to increase at least tenfold in the next few years.

In this situation, the ‘United Nations Committee for the Peaceful Use of Outer Space (UN COPUOS)’ included the International Astronomical Union’s (IAU) ‘Dark and Quiet Skies (DQS)’ protection recommendation in an official document at a meeting held in February this year. The recommendation proposes maintaining the brightness of low-orbit satellites at ‘level 7 or lower, invisible to the naked eye’ and presents it as the minimum standard to protect the optical and radio astronomy observation environment.

Recently, radio interference has become increasingly serious. According to a study published in the international academic journal ‘Astronomy & Astrophysics’ in July, more than 110,000 radio waves were detected from Starlink 1800 as a result of observing satellite signals for 29 days with Australia’s radio telescope ‘EDA2’. Some of them violated frequency bands protected by the International Telecommunication Union (ITU).

Jeong Tae-hyun, head of the KVN Center of the Observation Infrastructure Operation Headquarters of the Korea Astronomy and Space Science Institute (KAST) said, “There has been no domestic damage yet, but experimental verification is necessary as some of the reception bands of the Korea Space Radio Observation Network (KVN) may overlap with the Starlink communication frequency.”

Radio interference goes beyond simple frequency overlap and is also linked to the problem of electromagnetic wave emissions from the satellite itself. All electronic devices emit a certain level of electromagnetic waves, but there are currently no international standards regulating the amount of satellite emissions. As the number of satellites increases explosively, radio ‘noise’ also increases, which can have a serious impact on astronomical observations. To discuss this, the Wireless Communications Sector Consultative Body (ITU-R WP 7D) under the International Telecommunication Union is currently active. The role of the council is to establish international standards to protect astronomical observation frequencies from radio interference. In the case of Japan, before the Starlink service is approved in 2022, the government analyzed the impact of radio interference and prepared measures to protect astronomical observations. However, it is said that in Korea, approval for the Starlink service was granted without such procedures this year, causing great concern in the academic world.

● Nighttime solar power plant project also appears

To make matters worse, a project has also emerged to generate power using solar power even at night. American startup ‘Reflect Orbital’ is pursuing a ‘space mirror satellite’ project that reflects sunlight and delivers sunlight to solar panels even at night. We plan to launch the test satellite ‘Earendil-1’ in 2026 and conduct an experiment that illuminates a specific area brighter than the full moon. To this end, we recently applied for permission from the U.S. Federal Communications Commission (FCC). The goal is to launch up to 4,000 satellites by 2030 to realize nighttime solar power generation with ‘20% brightness of sunlight.’

Na-rae Hwang, senior researcher at the Large Telescope Research Center of the Observation Infrastructure Operations Headquarters of the Astronomical Research Institute, said, “If the light reflected by artificial satellites becomes brighter than the full moon, observation of dark celestial bodies becomes virtually impossible. There is research showing that not only optical telescope users but also some binocular users may be exposed to the risk of vision damage, so this could be an astronomical and environmental disaster.” warned.

Foreign media outlets are also questioning the feasibility of this plan, saying, “Even if it is technically possible, it is economically unrealistic.” However, as the cost of satellite launches has recently plummeted and competition in the launch vehicle market has intensified, there is also the possibility of an unreasonable push for ‘technology demonstration’ or ‘market dominance’.

● Korea must also participate in international cooperation

As reflected satellite light and radio interference have emerged as a global problem, the need for international cooperation is increasing. In May of this year, Korea officially joined the ‘Dark Skies and Quiet Skies (DQS) Friendly Countries Group’ under the International Astronomical Union (IAU). At the UN COPUOS meeting in June, it was emphasized that “DQS protection is a shared responsibility of humanity, and technology, policy, and international cooperation must go hand in hand.”

International discussions discussed ways to use satellite orbit information to predict the passage time and brightness for each observatory and adjust the observation schedule. Discussions continued on developing technology to reduce reflectivity and radio interference in cooperation with satellite operators, and sharing and institutionalizing information through international organizations. Astronomers are also seeking countermeasures by developing technology to automatically detect and remove noise and trajectory signals caused by satellites from observation data.

Senior researcher Hwang emphasized, “Astronomy research, which searches for the origins of the universe and traces of life, is not directly connected to daily life, but its results have made satellites and advanced space industries possible. We must jointly seek ways for the space industry to develop sustainably without interfering with astronomy.”