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

We report studies on 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. Starlink satellites with no brightness mitigation are presently g ~ 5.1 mag, and an initial experiment "DarkSat" is g ~ 6.1 mag. Future Starlink darkening plans may reach g ~ 7 mag, a brightness level that enables non-linear image artifact correction to the same level as background noise. However, the satellite trails will still exist at S/N ~ 100, generating systematics that may impact data analysis and limiting some science. LEO satellite trails are wider than a point-spread function because satellites are slightly out of focus due to their finite distance; for Rubin Observatory's 8.4-m mirror and a satellite at 550 km, this widening effect is about 3 arcsec, which helps avoid saturation by decreasing the trail's peak surface brightness.