Ducting occurs in the region of the atmosphere called the Troposphere. Tropospheric bending lets you contact stations farther away on the 2-meter band.
Tropospheric ducting is caused by a temperature inversion. A stable high-pressure system weather condition can cause tropospheric ducting. A widespread temperature inversion causes VHF radio waves to be propagated several hundred miles over oceans. It occurs most frequently in the UHF bands.
High-gain antennas are normally used for EME (moonbounce) communications to overcome the extreme path losses of this mode. A high-gain array of Yagi antennas would be the best choice for an EME (moonbounce) station.
Before two stations can conduct real-time communications through a satellite, it must be in view of both stations simultaneously. It is necessary to use higher transmitter power when conducting satellite communications via a satellite that is low to the horizon.