Radio astronomy and Starlink are a threat to Optical Astronomy

197 Radio Dishes to Close Down

A radio-quiet zone will be formed constituting the 197 radio astronomy dishes which is the size of Pennsylvania where even a cellphone is forbidden, to preserve the array’s views of the heavens in the Square Kilometre Array (SKA) in South Africa. The telescope, due to be completed in the late 2020s, cannot be saved from these precautions from our sky as it will be covered with tens of thousands of communications satellites focusing down radio signals straight from the heavens as stated by SKA Director-General Phil Diamond.

Radio astronomy and Starlink are a threat to Optical Astronomy
Square Kilometre Array (SKA) in South Africa

Starlink has its Mega Constellation

The rocket company SpaceX has already launched hundreds of Starlink satellites intended to provide internet service to remote areas known as the first “mega constellation”. As these satellites leave bright streaks across telescopes’ fields of view resulted in an aroused anger among the optical astronomers and now radio astronomers are also worried. This week an analysis of the impact that Starlink and other constellations by SKA were released that would have on the array. The analysis said that these dishes will be interface with one of the radio channels SKA plans to use and hamper organic molecules in space as well as water molecules used as a key marker in cosmology.

Starlink Stack of Satellites
Starlink Stack of Satellites

Radio Astronomers searching a Path

While radio astronomers are seeking regulations for means of the usage of these dishes while SpaceX is promising to address the concern. The United Nations Office for Outer Space Affairs (UNOOSA) is considering ways to keep satellites from polluting the night sky with light and radio signals, which discussed the SKA analysis at a workshop this week, showing concerns not only for astronomy but also for wildlife and the public. The involvement of the International Telecommunication Union (ITU), a U.N. organization, is also expected by the astronomers. Radio astronomer Michael Garrett, director of the Jodrell Bank Centre for Astrophysics in the United Kingdom said that the radio spectrum is a resource that is being consumed by private companies that typically have no regard for science, and the intervention of government can stop this state of affairs in his view.

Starlink Satellite Aims to Minimize Reflections

So far, SpaceX has won approval for 12,000 satellites and has launched more than 700 Starlinks out of an initial goal of 1440. Similar ambitions have been seen by other operators, such as OneWeb and Amazon’s Project Kuiper. Studies suggest with satellite tracks marring most images will leave wide-field optical surveys worst affected. The team building the Vera C. Rubin Observatory has been working with SpaceX to reduce the impact, it is a survey telescope in Chile due to see first light next year. The company has painted its satellites with a less reflective color and also changed the orientation of satellites as they move up to their final orbit along with fitted “visors” to reduce reflections. SpaceX’s Patricia Cooper, vice president for satellite government affairs told that since August, all launched Starlink satellites have visors in the UNOOSA workshop this week. She also stated that their company is looking for a path where both operations could sustain.

Bands may Become Unusable in Future

The analysis from SKA highlights the new concern as when complete will be the world’s largest radio observatory. The band that Starlink uses known as band 5b that is one of seven bands SKA’s South African dishes will target to beam down internet signals which takes up a range of frequencies from 10.7 to 12.7 gigahertz. The SKA analysis taking into account both direct signals and leakage called “side lobes” calculated the impact of 6400 satellites.

The team calculated that a 70% loss insensitivity in the downlink band will be bared by satellite transmissions. The entire band 5b would be unusable if the number of satellites in mega-constellations reaches 100,000 as predicted by many researchers. Molecules such as the simplest amino acid, glycine, which is a component of DNA will cause a loss in its sensitivity for SKA but if it was detected in a planetary system, it would have been a very interesting piece of information. SKA is opening up a new era with the new band, which could also contain tampered or hidden fingerprints of water molecules in distant galaxies, a tracer that is used by the cosmologists to study with the expansion of the universe, the acceleration of dark energy.

Map of satellites may destroy the recognizable fingerprints of galaxies
Map of satellites may destroy the recognizable fingerprints of galaxies

Is Coexistence the Solution?

Since 1959, several narrow frequency bands for astronomy has been protected by ITU. But digital receivers have allowed telescopes to operate over the whole spectrum in recent decades. Diamond says that coexistence with transmitters has been learned, talking for spectrum other than a radio-quiet zone or siting telescopes in remote areas. Although flowing transmitters are not in the control of astronomers.

Radio astronomers want the satellite when they are flying over a radio observatory to turn off their transmitters or move to other bands or point them away by the satellite operators. SpaceX is discussing these options as per Tony Beasley, director of the U.S. National Radio Astronomy Observatory. He also said that in the next year or two, they will be doing tests where they’re going to be trying to apply remedies in real-time with Space X. Beasley favored SpaceX that they do cool stuff but also they don’t want to do any harm to the world.

Recommendations by SpaceX

Other astronomers do not want to practice any goodwill. Two recommendations were pushed by SpaceX in the UNOOSA workshop that is all future satellites in low-Earth orbit be designed to avoid beaming at radio quiet zones and radio telescopes, and second is that they would control the leakage from their side lobes. Ideas discussed this week for protecting optical observatories along with these recommendations will be discussed at U.N. subcommittees next year before going to UNOOSA and ultimately in the U.N. General Assembly for approval.

Philosophically understanding the situation, Beasley said that SpaceX is legally transmitting inside one of their bands and there are going to be impacted for anyone trying to do radio astronomy. So basically debating about the ways of these satellite designs is need for the decade, and selling of these spectrums should be quite sensible.


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