Frequently Asked Questions
Q: Your model predicts a lot of satellite trails my telescope! Does this mean that the quality of the images will be bad?
A: Absolutely not. The objective of this repository is not to predict the quality of individual images, or even individual telescopes. Specific missions and constellations change, adapt, and sometimes, even be canceled. The forecasts are intended to provide an approximate representation of the impact of satellite constellations for space based astronomy as a whole, not for specific missions. Our ultimate mission is to provide a measurement of the expected level of artificial satellite light contamination if the current trend of industrial use of Low Earth Orbit by using several space-based observatories as examples of potential platforms. But the real value is not the specific number for existing telescopes or proposals, but the constraints that the current conditions impose in future missions, some of them which will be designed by scientists that are still at school or in their early career.
By doing that, we can give educated guesses of the level of contamination for present and future missions, enabling astronomers, industrial partners, and government agencies to plan more effectively and advocate for responsible satellite constellation management.
Q: My favorite telescope will combine many images to produce mosaics. Will this help reduce the impact of satellite trails?
A: Possibly yes. Satellites appear almost as randomized events, very rarely falling in the same position of the sky. By combining many images most of those trails can be removed. This is the case of the core missions for SPHEREx (IR cosmological mapping) and ARRAKIHS (low surface brightness astronomy). However, these science cases only represent a subset of all possible scenarios, and other science cases that rely on individual exposures or reduced datasets can be likely affected.
Q: But these satellite do not exist now, why should I care?
A: Humanity has launched to space in six years (2020-2026) more satellites than in the previous 60 years (1960-2020). Without any regulations, the number of satellites in orbit is expected to increase by a factor of 100 in the next decade, and the levels of light pollution will increase accordingly.
Contrary to the popular belief, light pollution is not a problem unique of ground-based astronomy. While forcing scientists to use space telescopes only (like Hubble) instead of ground ones (Vera C. Rubin) seems as a tempting solution, there are two problems: 1) space telescopes cannot possibly replace the thousands of different observatories on the ground and - as we demonstrate in this project - 2) satellites can contaminate space telescopes as well.
The results are clear. If the satellite constellations proposed by the industry become operational, up to 92% of the images of new telescopes like SPHEREx, ARRAKIHS, and Xuntian will be contaminated by satellites, showing tens to hundreds of satellite trails per image. Almost 40% of the images of Hubble will be contaminated as well. Their exact position and level of contamination over the images is extremely hard to predict, given the lack of information about the new satellites (orbits, reflectivity), but the efforts to identify, analyze, and attempt to remove this new source of contamination will dramatically increase the operational costs of the observatories and the quality of the astronomical images, maiming our capabilities to - for example - discover distant galaxies or new hazardous asteroids.
Q: Ok, that sounds scary. Is astronomy doomed?
A: No, but we need to act now. The good news is that the problem of satellite light pollution is solvable. We can find new ways to avoid satellite trails from photobombing our images, new ways to mitigate the impact of satellite trails in our data, and coordinate with the space industrial partners to optimize the configuration and number of the satellite constellations. For that reason, the International Astronomical Union (IAU) has created a Center for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference (CPS) to coordinate efforts between astronomers, industry, and government agencies to find solutions to this problem.
Q: How can I help?
Visit the website of the IAU-CPS and become a Member of the International Astronomical Union Centre for the Protection of the Dark and Quiet Sky! (link here).
If you would like to get involved in our team, feel free to email us.
Q: How often are forecasts updated?
A: Forecasts will updated as new satellite and observatory data become available. We aim to provide updates at least quarterly, but significant changes in satellite constellation plans or new mission data may trigger more frequent updates.
Q: Can I access historical forecasts?
A: Yes, the Zenodo repository maintains an archive of historical forecasts. You can retrieve:
Simulated trails for each forecast version, including the spectral energy distribution of the trails.
Observational parameters, such as pointing coordinates, orientation, exposure times, Sun, Moon, and Earthshine levels for each exposure.
The size of the satellite population considered in each forecast version.