Astronomers renew concerns about Starlink satellite brightness

PASADENA, Calif. — As SpaceX gears up for another launch of Starlink satellites, astronomers are concerned the company maybe backsliding in its efforts to reduce the brightness of those satellites.

A Falcon 9 is scheduled to lift off at 12:08 p.m. Eastern June 17 from Kennedy Space Center’s Launch Complex 39A, placing 53 Starlink satellites into orbit. This mission will bring the total number of Starlink satellites launched to more than 2,700, with more than 2,450 in orbit.

These satellites, like several hundred before it, are version 1.5 of the Starlink design. Those satellites lack visors that SpaceX installed on satellites in 2020 to keep sunlight from reaching reflective surfaces on the satellites and thus reduce their brightness as seen from the ground. The visors were not compatible with the laser intersatellite links installed on the V1.5 satellites.

Astronomers say they’ve noticed the V1.5 satellites are brighter than the earlier “VisorSat” Starlink satellites. During a panel discussion at the 240th Meeting of the American Astronomical Society (AAS) here June 13, Pat Seitzer, an astronomer at the University of Michigan who studies satellite brightness, said the VisorSats were at magnitude 6.5. That brightness was near the recommendation set by astronomers of being no brighter than magnitude 7 to minimize interference with astronomical observations.

However, the V1.5 Starlink satellites are about half a magnitude brighter than the VisorSats. “In a real sense, we’re going backwards here,” he said. “We have to talk to SpaceX and see what their eventual plans on this are.”

A bigger concern is the second generation of Starlink satellites. Those satellites, designed to be launched on SpaceX’s Starship, will be significantly larger and, thus, potentially brighter. “It’s anybody’s guess what the brightness will be,” Seitzer said. “Hopefully they can incorporate all of the lessons they’ve learned so they don’t end…


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