  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.
