Palomar survey instrument analyzes impact of Starlink satellites

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There have been more internet satellites in the sky since 2019. The Starlink satellite constellation now has over 1,700 members. Astronomers are concerned that these objects, which can appear as streaks in telescope images, could hamper their scientific observations.

A team of researchers studied archival images captured by the National Science Foundation-funded Zwicky Transient Facility, an instrument that operates from Caltech's Palomar Observatory near San Diego. The entire night sky is scanned every two days by ZTF. This includes everything from asteroids to supernovae. The team members decided to study the effects of the Starlink satellites because they are the largest low- Earth orbit, orLEO, constellation.

The January 17 issue of The Astrophysical Journal Letters shows 5,301 satellite streaks in archival images. It is important for finding near-Earth asteroids that appear close to the sun in the sky if you take twilight observations at dawn or dusk. The first asteroid spotted with an ellipse that fits within the circle of Venus is 2020 AV2.

Przemek Mrz, the study lead author and a former Caltech scholar, says that almost 20 percent of twilight images have been affected.

After the Starlink constellation reaches 10,000 satellites, the scientists expect that nearly all of the ZTF images taken during twilight will contain at least one streak.

"We don't expect Starlink satellites to affect non-twilight images, but if the satellite constellation of other companies goes into higher orbits, this could cause problems for non-twilight observations," Mrz says.

The new report states that the ZTF science operations have not been affected by the increase in image streaks. The paper shows that a single streak affects less than a tenth of a percent of the images.

There is a small chance that we would miss an asteroid or another event hidden behind a satellite streak, but compared to the impact of weather, such as a cloudy sky, these are rather small effects for ZTF.

Prince says that software can be developed to help mitigate potential problems, for example, software could predict the locations of the Starlink satellites and thus help astronomer avoid scheduling an observation when one might be in the field of view. Astronomers can use software to see if a passing satellite has an effect on an astronomy observation.

The visors on the Starlink satellites were looked at in the new study. The visors reduce the satellite's brightness by a factor of five. The satellites are dim because of that, and the stars are not as bright as we can see with our eyes.

This is not dim enough to meet the standards outlined in the SATCON1 workshop in 2020, a gathering sponsored by the NOIRLab and the AAS. The group called for all the satellites to be at a higher altitude.

The study authors note that their study is specific to ZTF. The Vera C. Rubin Observatory will also survey the sky nightly, but due to its more sensitive imager, it may be more negatively affected by satellite streaks than ZTF.

The impact of the SpaceX Starlink Satellites on the Zwicky Transient Facility Survey Observations was written by Przemek Mrz. There is a book titled "10847/2041-8213/ac470a".

The Astrophysical Journal Letters contains information.

The Palomar survey instrument analyzed the impact of Starlink satellites on January 17th.

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