With an increasing number of satellites in the sky, astronomers have repeatedly raised concerns about how these satellites could affect scientific research. Earlier this year, a study of Hubble Space Telescope observations showed how some images were being messed up by streaks of light from satellites, and while only a small percentage of Hubble images were affected, the authors raised concerns that that with the projected number of satellites set to explode in the next decade, the problem could become serious.
Now, astronomers at the Space Telescope Science Institute (STScI), which runs Hubble, have devised a tool to deal with satellite streaks in Hubble images. “We developed a new tool to identify satellite tracks that is an improvement over previous satellite software because it is much more sensitive. So we think it will be better to identify and remove satellite traces in the Hubble images,” STScI’s Dave Stark said in a release.
The tool works by looking for traces in images from one of Hubble’s cameras, the Advanced Camera for Surveys. This camera has a very wide field of view, which means it captures a large part of the sky at one time. That is useful in this case because it means that the satellite trails will only interrupt a very small percentage of the image.
“The average width that I measured for the satellites was 5 to 10 pixels. The widest view of the ACS is 4,000 pixels wide, so a typical trail will affect less than 0.5% of a single exposure,” Stark said. “So not only can we mark them, but they don’t affect most pixels in the individual Hubble images. Even as the number of satellites increases, our tools for cleaning up the images will continue to be relevant.”
When Hubble takes an image, it actually captures multiple exposures of its target. So a satellite trail would typically be on a single exposure, and the tool can look at multiple exposures and use that data to highlight the affected area. The researchers can then combine data from the different exposures to edit the streak.
This type of approach will become even more important as the number of satellites in the sky continues to grow, the team writes in their article describing the research. However, for now, Hubble remains only minimally affected.
“To date, these satellite trails have not had a significant impact on research with Hubble,” said Tom Brown, head of STScI’s Hubble Mission Office. “Cosmic rays hitting the telescope’s detectors are a major nuisance.”