Bombardment

Weapon Special Rule
Bombardment weapons can't be used against other ships or orbital assets, only ground sectors. In order to fire a bombardment weapon a ship must be in Low Orbit or Atmosphere. NB, only ships with a specific rule (eg Low Level) may bombard from atmosphere. Ships without specific special rules allowing them to bombard from atmosphere may not do so.

Unlike other weapon systems bombardment weapons incur no penalties for firing through orbital layers or shooting through atmostphere - it's what they're made for.