Satellite Constellation Avoidance with the Rubin Observatory Legacy Survey of Space and Time

Abstract

We investigate a novel satellite avoidance strategy to mitigate the impact of large commercial satellite constellations in low-Earth orbit on the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). We simulate the orbits of currently planned Starlink and OneWeb constellations (∼40,000 satellites) to test how effectively an upgraded Rubin scheduler algorithm can avoid them, and assess how the overall survey is affected. Given a reasonably accurate satellite orbit forecast, we find it is possible to adjust the scheduler algorithm to effectively avoid some satellites. Overall, sacrificing 10% of LSST observing time to avoid satellites reduces the fraction of LSST visits with streaks by a factor of 2. Whether such a mitigation will be required depends on the overall impact of streaks on science, which is not yet well quantified. This is due to a lack of adequate information about satellite brightness distributions as well as the impact of glints and low surface brightness residuals on alert purity and systematic errors in cosmological parameter estimation. A significant increase in the number of satellites or their brightness during Rubin Operations may make implementing this satellite avoidance strategy worthwhile.

Tuning the Legacy Survey of Space and Time (LSST) Observing Strategy for Solar System Science

“…A recent study by Hu et al (2022) finds that ∼10% of all LSST images will have a streak from a launched or planned-tobe-launched Starlink (Generation 1 or 2) or OneWeb satellite, with observations in twilight more frequently impacted. If significantly more satellites are launched over the next several years, more LSST observations could have streaks.…”

“…Illuminated satellites are most numerous near the horizon close to dawn and dusk; the low-SE twilight microsurvey runs in −12°solar elevation and darker. For the low-SE twilight microsurvey (Section 4.7.1), the effects of satellite constellations will be particularly pronounced, with some 90% of images expected to be impacted with at least one streak per image (Hu et al 2022).…”

“…It may be possible for the Rubin Observatory scheduler to selectively observe specific pointings on the sky, which could decrease the number of WFD images with satellite streaks by a factor of two. However, this would come at the substantive cost of ∼10% of the LSST observing time (Hu et al 2022). The tradeoffs of implementing this algorithm would depend on the impact of the satellite streaks on LSSTCam, which, as noted above, has yet to be fully characterized, and the number, sky distribution, and apparent magnitude of satellites at the start of Rubin science operations.…”

Stellar Variability in Ground-Based Photometric Surveys: An Overview

“…In the words of Green et al (2022), "unlike sources of ground-based light pollution requiring cooperation and control by local regulation, limiting the strongly negative impact of satellite constellations requires cooperation and possible regulation at national and international level." Green et al (2022) Implementing active avoidance when scheduling observations may be helpful (Hu et al 2022a), but this may be hampered by the lack of (or insufficiently accurate) published ephemerides (Cui & Xu 2022).…”

Satellite Optical Brightness

“…This is expected to increase exponentially over the next decade. The impact on astronomy research (Tyson et al 2020;Hu et al 2022) and on the night sky environment (Venkatesan et al 2020;Lawrence et al 2022;Barentine et al 2023) has been discussed widely. Technical mitigation involves innovation in satellite design, satellite operations, and astronomy data processing and analysis.…”