Astrosat: Forecasting satellite transits for optical astronomical observations

TL;DR

Astrosat is a tool that predicts satellite transits in the sky for ground-based astronomers, helping them avoid or mitigate satellite trail interference in their observations.

Contribution

The paper introduces Astrosat, a novel tool for projecting satellite orbits onto celestial coordinates to assist astronomers in planning observations amidst increasing satellite constellations.

Findings

Astrosat can accurately project satellite transits for specific observer locations and times.

A typical observatory can expect to see up to 5 Starlink satellites at twilight, increasing to 30 with full constellation deployment.

The tool enables mitigation strategies like avoiding intersections or post-processing corrections.

Abstract

The impact of large-scale constellations of satellites, is a concern for ground-based astronomers. In recent years there has been a significant increase in the number of satellites in Low-Earth Orbit and this trend is set to continue. The large number of satellites increases the probability that one will enter the field of view of a ground-based telescope at the right solar angle to appear bright enough that it can corrupt delicate measurements. We present a new tool Astrosat that will project satellite orbits onto the RA/DEC coordinate system for a given observer location and time and field of view. This enables observers to mitigate the effects of satellite trails through their images by either avoiding the intersection, post-processing using the information as a prior or shuttering the observation for the duration of the transit. We also provide some analysis on the apparent brightness of the largest of the constellations, Starlink, as seen by a typical observatory and as seen with the naked eye. We show that a naked eye observer can typically expect to see a maximum of 5 Starlink satellites at astronomical twilight, when the sky is dark. With the intended 40000 satellites in the constellation, that number would increase to 30.