Researchers study the impact of Starlink satellites on astronomy

As SpaceX sends another rocket into space this week on a mission to expand its Starlink constellation to around 2,000 satellites, astronomers are digging into a newly released report assessing the impact of satellites on observations. from deep space.

Ever since SpaceX began deploying batches of Starlink internet satellites in 2019, astronomers have raised concerns about how sunlight reflecting off the small devices could obscure their view of space and impact their job.

To assess their impact, a team led by former Caltech researcher Przemek Mróz studied archival footage captured at dusk by the Zwicky Transient Facility (ZTF) at Caltech’s Palomar Observatory near San Diego.

The team’s findings, which appeared in the January 17 issue of The Astrophysical Journal Letters, found that in 2019 only 0.5% of twilight images showed trails from Starlink satellites, that figure had risen to 18% by August 2021, suggesting that if SpaceX expands its constellation to 10,000 (for which spaceflight has already received deployment approval), then just about all ZTF imagery captured at dusk will be affected.

We found that twilight observations are particularly affected: a fraction of streaky images increased from less than 0.5% in late 2019 to 18% in August 2021. Once SpaceX deploys 10,000 Starlinks, virtually all ZTF images taken at dusk could be affected. pic.twitter.com/5f8tKaSHlk

– Przemek Mróz (@przemroz) January 17, 2022

However, study co-author Professor Tom Prince of Caltech noted that a single streak of light from a Starlink satellite affected less than a tenth of a percent of the pixels in a ZTF image.

“There is a small chance that we miss an asteroid or other event hidden behind a series of satellites, but compared to the impact of weather, such as cloudy skies, these are rather small effects for ZTF,” Prince said.

In 2020, SpaceX chief Elon Musk said he wanted to work with astronomers to make sure Starlink satellites didn’t interfere with their work.

To that end, SpaceX has started adding visors to its satellites to reduce the brightness of the reflection. The team investigated the effectiveness of the visors and found that with ZTF observations, the accessory reduced a satellite’s brightness by a factor of around five – a level that fell short of the set standards. by a 2020 Satellite Constellations 1 (SATCON1) workshop that brought together astronomy groups.

Prince said the software could help overcome potential problems – for example, using computer intelligence to predict the positions of Starlink satellites, allowing astronomers to plan their observations for the clearest view. The software can also be used to determine if a passing satellite has negatively impacted an observation that has already taken place, allowing astronomers to view the resulting image in the appropriate context.

Mróz said his team did not expect Starlink satellites to affect non-twilight images, but cautioned that if other companies’ satellite constellations were deployed in higher orbits, non-twilight observations could also be affected. affected.