  We introduce a simple coordinate system covering half of de Sitter space. The
new coordinates have several attractive properties: the time direction is a
Killing vector, the metric is smooth at the horizon, and constant-time slices
are just flat Euclidean space. We demonstrate the usefulness of the coordinates
by calculating the rate at which particles tunnel across the horizon. When
self-gravitation is taken into account, the resulting tunneling rate is only
approximately thermal. The effective temperature decreases through the emission
of radiation.
