[KISTI과학향기]Satellite Internet Starlink disrupts astronomical observations?

Elon Musk, who leads the electric vehicle company Tesla Motors and the private space company SpaceX, is a person with aspirations to change the world with technology. In particular, SpaceX has performed so much that it overwhelmed space organizations and military industry companies with long-standing know-how and technology such as NASA and Lockheed Martin. SpaceX, for example, launched the Falcon 9 rocket to orbit the satellite and was the first to fully recover the propellant rocket. This drastically reduced the cost of launching a rocket, making it possible to dream of a future where rocket launches become commonplace.

◇ Dream of connecting the world with high-speed Internet

Space with such great technology There is another innovative project that is currently ambitious. It is the’Starlink Project’. The Starlink project is a massive plan to build a high-speed satellite internet network for the world. To this end, SpaceX has declared that it will launch more than 13,000 communication satellites.

The satellites launched by the Starlink project are not micro-satellites weighing less than 100kg called Microsets, but small satellites weighing more than 200kg. It will launch 7,518 such satellites at an ultra-low altitude of approximately 340 km, and 4425 satellites at a low altitude of approximately 1,110 km. People also said that Elon Musk dreams of an impossible dream because it is a huge project, but it received a $1 billion investment from Google and a private equity fund and launched a test launch in 2018 with permission from the U.S. government. It launched 60 link satellites simultaneously for the first time. This satellite was also a test satellite to test several network equipment. Finally, in November 2019, an additional 60 Starlink satellites for actual operation were successfully launched. As of March 7, 2021, SpaceX launched 1,205 Starlink satellites, of which 1141 are orbiting the Earth, excluding those that have departed.

The Starlink project provides broadband Internet service by connecting thousands or tens of thousands of communication satellites. That is why the Internet is provided to all corners of the world and remote areas that have never been visited. In addition, since it transmits radio waves from the ground to a low-orbit satellite at the speed of light and connects the satellite with a laser signal, it is much faster than an optical cable. If the StarLink project is completed, there is a rosy prospect that the world will be digitalized.

◇The great plan rather hinders humanity’s search for knowledge?

However, a serious phenomenon occurred that the Starlink project could rather interfere with human knowledge accumulation and space exploration. There are so many Starlink satellites that they are causing light pollution that interferes with the observation of stars by astronomers. When 60 Starlink satellites were launched, 60 satellites were observed moving in sequence like a train. This was spectacular, but when astronomers took celestial photographs, the Starlink satellites obstructed observations by blocking stars or reflecting sunlight. The Association of Astronomical Research Colleges (AURA) said in a statement, “Because of the light scattered from bright satellites, it may be difficult to observe astronomical objects that require long exposures when taking pictures. In particular, asteroids near Earth are more affected because they are mainly observed at dawn or early evening.”

In addition, starlink satellites that have reached the end of their life can turn into space debris that orbits the Earth for years before entering the atmosphere and extinction naturally as heat. If so, satellite launch would be impossible until the massive satellite debris disappears. So far, 64 Starlink satellites have been out of orbit, but if tens of thousands of satellites are launched into space, it is impossible to estimate how many more satellites will leave.

In response, SpaceX announced that it would put an awning on each Starlink satellite so that it would not interfere with the observation of the night sky by astronomers on the ground, and launched 57 satellites with awnings in August 2020. The sunshade can be folded and unfolded like a sun visor on the top of a car windshield. During the elevation after launch, the sunshade is attached flat to the satellite and unfolds after being separated from the second-stage rocket. This will solve the problem of satellite light reflection and overheating at the same time, but we need to watch more. In addition, SpaceX said that to solve the problem of space debris, Starlink satellites have been designed so that they can de-orbit themselves and burn quickly when their lifespan is over.

The StarLink project, which is to supply the Internet to the world so that there are no communication underprivileged, seems to be unconditionally good, but as in our life, it has one and one side. In the future, I hope that it will be a project that can improve problems and deliver only the strengths to the world.

Written by: Wonho Won Science Columnist