Mitigation of LEO Satellite Brightness and Trail Effects on the Rubin Observatory LSST

TL;DR

This paper explores various strategies to reduce the optical impact of bright LEO satellites on the Rubin Observatory LSST, including pointing adjustments, sensor corrections, satellite darkening, and follow-up observations, to mitigate systematic errors in astronomical data.

Contribution

It presents new methods and experimental results for satellite trail mitigation, satellite darkening techniques, and their effects on LSST image quality and data analysis.

Findings

Darkening Starlink satellites reduces brightness to g ~ 7 mag.

Trail width at 550 km altitude is about 3 arcseconds, aiding in artifact correction.

Approximately 1% of pixels in twilight images could be masked due to satellite trails.

Abstract

We report studies on the mitigation of optical effects of bright low-Earth-orbit (LEO) satellites on Vera C. Rubin Observatory and its Legacy Survey of Space and Time (LSST). These include options for pointing the telescope to avoid satellites, laboratory investigations of bright trails on the Rubin Observatory LSST camera sensors, algorithms for correcting image artifacts caused by bright trails, experiments on darkening SpaceX Starlink satellites, and ground-based follow-up observations. The original Starlink v0.9 satellites are g ~ 4.5 mag, and the initial experiment "DarkSat" is g ~ 6.1 mag. Future Starlink darkening plans may reach g ~ 7 mag, a brightness level that enables nonlinear image artifact correction to well below background noise. However, the satellite trails will still exist at a signal-to-noise ratio ~ 100, generating systematic errors that may impact data analysis and limit some science. For the Rubin Observatory 8.4-m mirror and a satellite at 550 km, the full width at half maximum of the trail is about 3" as the result of an out-of-focus effect, which helps avoid saturation by decreasing the peak surface brightness of the trail. For 48,000 LEOsats of apparent magnitude 4.5, about 1% of pixels in LSST nautical twilight images would need to be masked.