Away mission

An away mission was a mission carried out by an away team outside of their starships or starbases. When transporters were unusable, shuttlecraft took over. Away missions varied in nature from survey missions, to medical relief and combat.

Second officers were expected to be involved and lead away missions. 

Excursion jackets and environmental suits provided more protection against hazards and the elements than the standard uniforms could. (Starship Farragut, Star Trek: Prometheus)