Scientists Alarmed By Increased Brightness Of New Starlink Satellites

A new study published last week by a group of scientists found that SpaceX’s new Starlink satellites are 4.9 times brighter than previous generations of Starlink satellites. Scientists are concerned that the constantly increasing number of satellites and spacecraft in orbit is inconveniencing astronomical observations. The excessive, man-made brightness of the sky directly affects astronomical observations, both radio and optical.

New Starlink Satellites Threaten Future Astronomical Observations

The study was led by Anthony Mallama of the International Astronomical Union’s International Astronomical Union Centre for Dark and Quiet Sky Protection from Satellite Constellation Interference (IAU CPS). Mallama is a senior engineer at Raytheon and the author of numerous technical papers and articles discussing the brightness of Starlink.

Mallama and several other amateur astronomers collected their data for the research. In their paper, they characterize the brightness of the Starlink satellites and reassess the impact of all Mini satellites.

The results show that “the average apparent stellar magnitude of the Starlink Mini Direct-To-Cell (DTC) satellites is 4.62, while the average stellar magnitude corrected for a uniform distance of 1000 km is 5.50. The DTC is on average 4.9 times brighter than other Starlink Mini spacecraft at a normal distance.”

Based on their lower altitude, preliminary estimates suggest that DTC will be about 2.6 times brighter than the others. At the same time, the negative impact of DTC satellites on astronomical observations is partially compensated for by spending more of their time in the Earth’s shadow than satellites in higher orbits.

Astronomers vs. satellite companies – who wins?

The study results from painstaking work over the past four years by astronomers at the International Astronomical Union to quantify and disseminate information on the impact of satellite constellations on existing and future astronomical facilities. Since 2020, Anthony Mallama has published 24 papers on this topic on the arXiv server.

Also, earlier in February this year, the International Astronomical Union submitted a short version of a report on the impact of these satellites to a subcommittee of the UN Committee on the Peaceful Uses of Outer Space (COPUOS), along with some recommendations to mitigate the loss of an unobstructed night sky.

The astronomers persuaded the United Nations Committee to examine how large satellite networks affect their field of work, potentially leading to greater regulatory oversight.

The “Wild West” of the starry sky

Starlink satellites, like Iridium satellites before them, can sometimes “flash” if their solar panels are positioned at the right angle to cast a burst of reflected sunlight towards Earth, briefly increasing their apparent brightness to potentially rival Venus or Jupiter.

“Satellite constellations … strike at the very heart of humanity’s scientific and cultural relationship to the night sky, influencing thousands of years of celestial traditions and cultural practices of all peoples around celestial cycles and the night sky,” physicists Aparna Venkatesan, James Lowenthal, Parvathy Prem, and Monica Vidaurri write in Nature Astronomy. “Treating space as a ‘Wild West’ frontier that demands conquest continues to encourage claims from those who are well endowed with resources.”

Instead of the Wild West, they argue, we should think of the night sky “as an inherited global commons” containing “the legacy and future of humanity’s scientific and cultural practices.”

Astronomers vs. Satellite Companies

Eric Perlman, an astrophysicist at the Florida Institute of Technology, says that satellites have interfered with astronomical observations ever since the first was launched. This is nothing new. However, with the increase in satellite constellations, this interference is reaching a new level.

He explained that in the telescope’s field of view, this bright object passes in about 10-15 seconds, disrupting the entire image, not just a few pixels.

At sunrise and sunset, the satellites are visible to the naked eye because the sun reflects off their details. Because these satellites are very close and reflective, they are often visible to the naked eye. But even if they were significantly obscured, they would still be visible to powerful telescopes used in astronomy if a satellite crossed their path. When a satellite comes into a telescope’s field of view, it can spoil the image, or at least give astronomers more work to correct it.

Hubble has already ruined some of its images due to Starlink satellites passing through.

This has led to talk of the need for a coordination agreement with Starlink to balance the interests of science and telecoms companies.

When there are multiple competing interests, those entities should work together, but under our current political situation, that is just too much to ask. For each side, it will be our way or the highway.

SpaceX is aware of this problem and is working with the astronomical community

The company is open to dialogue and is trying to dim the exterior of its satellites to limit their brightness. SpaceX has had to invest in developing a mirror film amid concerns that Starlink satellites reflect too much sunlight from Earth’s orbit and amid the photobombing of astronomical images.

The first-generation Starlink satellites previously came with built-in “sun shields” to prevent sunlight from reaching the equipment, but they created atmospheric drag and required the satellites to use more fuel. To replace the visors, SpaceX said it is developing “RF (radio frequency) transparent mirror films” to soften sunlight reflections.

The dielectric mirror film on the second-generation Starlink satellites is designed to scatter sunlight away from Earth, preventing interference with ground-based astronomy. The stated goal is to make their next generation of satellites invisible to the naked eye, and they appear to be well on their way to achieving this goal.

In some cases, observers trying to calculate the effective brightness of the satellites could not even see them with their observing equipment – meaning that the satellites were less bright than even the dimmest stars at the time.

Background

SpaceX launched the first six Starlink Mini Direct-To-Cell (DTC) satellites on 3 January 2024. After successfully testing the first batch in orbit, the company applied to the US Federal Communications Commission for a license modification. The change will allow 7,500 DTC spacecraft to orbit at altitudes between 340 and 345 kilometers.