All Upgraded Ships
On the main menu, press: 
Right, L1, Up, Up, Down, Right, R2, L2, R2, Down, Up, Down 
and you will hear an explosion. Start a game with any ship, 
then quit. You should now have all four upgraded ships with 
which to start on Sector 5. 
Wraith Ship
Once you've got the four upgraded ships (see above), enter 
this code on the main menu: 
Left, Right, L1, Left, Right, L1, R2, R2, L2, Left, Right, Up 
and you will hear an explosion. As before, start a game, 
then quit. You'll now be able to select the Wraith ship and 
start on Sector 8. 
Planet Heads
On the main menu, press: 
Down, Up, L1, Right, L1, Up, Right, Select, Right, R2, L1, L2 
and you will hear an explosion. This gives you the first four 
levels with the faces of the programmers instead of planets. 
The next four levels have cheese and stuff instead of planets, 
then the game reverts to normal. 
Note:
This won't work if either of the first two cheats has 
been entered. 
Extra Missions
On the main menu, press: 
L1, Left, L2, Down, Select, Left, Down, R2, R2, R2, Select, Up 
amd upi will hear an explosion. This gives you four extra 
missions, where you are in one of the spacecraft fighting 
World War II planes and fighter bombers etc. 
Note:
This won't work if either of the first two cheats has been entered. 

By: loginr