Courage -- Death of Hijikata! - S2.E21

The Comet Empire main fleet makes their final stand at Saturn. General Bleak's Magna Flame gun manages to destroy a sizeable chunk of the Earth fleet. Earth's remaining forces retreat to Saturn's ice rings wherein they ambush the Comet Empire forces.

The Argo, late to join Captain Gideon's fleet, is not able to participate the the main battle but sends fighter squadrons.

After defeating the Comet Empire fleet, the combined force of all the Wave-Motion Guns in Earth's fleet succeeds in disabling the plasma vortex that enshrouds the Comet Empire fortress. But, the secondary plasma shield that covers the upper half of the fortress remains operational, and the Comet Empire's main belt guns manage to wipe out the entire EDF fleet. Captain Gideon and his Andromeda crash headlong into the Comet's plasma vortex but not before radioing a message to the Star Force that they should attack from the bottom.

Note: This episode features the really grooving version of the Comet Empire theme, as Bleak's fleet plunges into the heart of the Earth Defense forces.