June 21, 2024
1 Solar System Way, Planet Earth, USA

Starlink flares can fool anyone, even airline pilots – Sky & Telescope

Starlink shines over the Utah desert
This composite image captured by photographer Jeff Warner in Wayne County, Utah, captures 17 minutes of intense flares in the pre-dawn hours, predominantly from Starlink satellites.

Satellite flares are eye-catching phenomena that have become familiar to an increasing number of skywatchers as SpaceX continues to launch dozens of Starlink satellites at a time. Some observers enjoy the novelty of these flares and like to see them, while others are simply confused by their appearance. Others despair because these flares interfere with their appreciation of the night sky.

There are also more practical concerns. Flares from numerous Starlink satellites, launched by SpaceX to provide broadband Internet, can deceive airline pilots and even pose a risk to air safety.

Douglas Buettner (University of Utah) led a study, presented at the Fourth IAA Conference on Space Situational Awareness, which examined the case of five pilots of two commercial airliners flying transpacific routes who saw several bright moving objects. The pilots took two cell phone photographs and one video. While pilots reported these objects as “unidentified aerial phenomena,” Buettner and his colleagues used aircraft flight data as well as satellite ephemeris to identify these objects as part of a train of closely spaced Starlink satellites. , released that same day.

iPhone image of an elongated object above the clouds with some stars in the background
In this image, which shows details of a pilot's photograph, the elongated object is a train of closely spaced Starlink satellites. Buettner and his colleagues identified the background stars using the publicly available software package astrometry.net.
Buettner et al. 2024

Buettner's team measured the brightness of the Starlink satellites in the photographs using SAOImage DS9 image analysis software. Using the star Castor as a luminosity reference, they discovered that the elongated object was magnitude –4, as bright as Venus. Such a bright light, if not identified correctly, could be misinterpreted as a nearby aircraft.

Meanwhile, retired astronomer Richard Cole had developed a numerical model to predict the brightness of the Starlink satellites and, based on that model, had predicted that under certain conditions the Earth-facing side of the Starlink chassis would reflect a mirror image of the Sun. . to observers on the ground. Observers would see this brief improvement as a flare.

When Buettner's study appeared, I was collecting brightness measurements to verify Cole's model. I saw satellites shining with an intensity of magnitude –2, equivalent to another Jupiter in the sky. Further analysis revealed that observers in planes flying at high altitude could see even brighter flares.

Cole's model can explain the brightness of the pilots' reports, because the plane, satellites and the Sun were in exactly the right configuration, as we reported in a study published on arXiv.

Sunlight reflects off the dielectric coating on the nadir side of a Starlink chassis. The coating is effective at mitigating glare when spacecraft are overhead and sunlight reflects back into space.
Star Link

It's easy to see Starlink's bright flares for yourself. The geometry requires that the Sun be between 25° and 30° below the horizon and that the Starlink satellites be between 5° and 10° above the horizon. Flares can also become visible under other circumstances, but they are usually not as bright. Bob King, science and technology contributing editor reported Last November, a group of amateur astronomers had observed Starlink flares from Oklahoma.

Photographer Jeff Warner first captured this type of Starlink flare in April 2023. Since then, she has been photographing them year-round from Utah and Colorado and has documented significant seasonal changes in their brightness.

Warner has also observed that the flare occurs primarily in one type of Starlink orbital shell: those that are inclined at 53° to Earth's equator. These projectiles currently make up the majority of the satellite constellation. As more orbital layers become populated, Warner believes the flare phenomenon may become visible from more southern latitudes, which could increase the number of pilot reports in the future.

Dozens of Starlink flares over a rugged landscape in dawn light
Earth's shadow is outlined in satellite flares, reflections of satellites within the 53° inclined orbital shell of the Starlink constellation. Captured May 6-7 from San Juan County, the composite image lasts four hours. The center of the lower convex arc traced by the flare shows the farthest northward reach of these spacecraft; These satellites rose 540 kilometers above Edmonton in Alberta, Canada, more than 1,000 miles to the north.
Jeff Warner

The research Cole and I are conducting contributes to a global effort to address the impact of satellite constellations. These efforts are coordinated by the Center for the Protection of Dark and Quiet Skies against Interference from Satellite Constellations of the International Astronomical Union.

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