The planet creation in Met_22Diplomatic (I'm assuming this is the mission you are refering to) is as follows:
void tPlanetTeam::mCreateShipsForTeam()
{
int32 planetDice = fMissionInfo->mRandomInt32( 1, 100 );
if( planetDice < 6 )
{
mCreateShip( typeid( tPlanet ), "PL1", kStartPosition_Z, kNoMetaShipID,
-1, 0, 0, -1, -1, NULL, kDefaultShipOptions );
}
else if( planetDice < 12 )
{
mCreateShip( typeid( tPlanet ), "PL2", kStartPosition_Z, kNoMetaShipID,
-1, 0, 0, -1, -1, NULL, kDefaultShipOptions );
}
else if( planetDice < 18 )
{
mCreateShip( typeid( tPlanet ), "PL3", kStartPosition_Z, kNoMetaShipID,
-1, 0, 0, -1, -1, NULL, kDefaultShipOptions );
}
else if( planetDice < 24 )
{
mCreateShip( typeid( tPlanet ), "PL4", kStartPosition_Z, kNoMetaShipID,
-1, 0, 0, -1, -1, NULL, kDefaultShipOptions );
}
else if( planetDice < 30 )
{
mCreateShip( typeid( tPlanet ), "PL5", kStartPosition_Z, kNoMetaShipID,
-1, 0, 0, -1, -1, NULL, kDefaultShipOptions );
}
else if( planetDice < 36 )
{
mCreateShip( typeid( tPlanet ), "PL6", kStartPosition_Z, kNoMetaShipID,
-1, 0, 0, -1, -1, NULL, kDefaultShipOptions );
}
else if( planetDice < 42 )
{
mCreateShip( typeid( tPlanet ), "PL7", kStartPosition_Z, kNoMetaShipID,
-1, 0, 0, -1, -1, NULL, kDefaultShipOptions );
}
else if( planetDice < 48 )
{
mCreateShip( typeid( tPlanet ), "PL7", kStartPosition_Z, kNoMetaShipID,
-1, 0, 0, -1, -1, NULL, kDefaultShipOptions );
}
else if( planetDice < 54 )
{
mCreateShip( typeid( tPlanet ), "PL9", kStartPosition_Z, kNoMetaShipID,
-1, 0, 0, -1, -1, NULL, kDefaultShipOptions );
}
else if( planetDice < 60 )
{
mCreateShip( typeid( tPlanet ), "PL10", kStartPosition_Z, kNoMetaShipID,
-1, 0, 0, -1, -1, NULL, kDefaultShipOptions );
}
else if( planetDice < 66 )
{
mCreateShip( typeid( tPlanet ), "PL11", kStartPosition_Z, kNoMetaShipID,
-1, 0, 0, -1, -1, NULL, kDefaultShipOptions );
}
else if( planetDice < 72 )
{
mCreateShip( typeid( tPlanet ), "PL12", kStartPosition_Z, kNoMetaShipID,
-1, 0, 0, -1, -1, NULL, kDefaultShipOptions );
}
else if( planetDice < 78 )
{
mCreateShip( typeid( tPlanet ), "PL13", kStartPosition_Z, kNoMetaShipID,
-1, 0, 0, -1, -1, NULL, kDefaultShipOptions );
}
else if( planetDice < 84 )
{
mCreateShip( typeid( tPlanet ), "PL14", kStartPosition_Z, kNoMetaShipID,
-1, 0, 0, -1, -1, NULL, kDefaultShipOptions );
}
else if( planetDice < 90 )
{
mCreateShip( typeid( tPlanet ), "PL15", kStartPosition_Z, kNoMetaShipID,
-1, 0, 0, -1, -1, NULL, kDefaultShipOptions );
}
else if( planetDice < 95 )
{
mCreateShip( typeid( tPlanet ), "PL16", kStartPosition_Z, kNoMetaShipID,
-1, 0, 0, -1, -1, NULL, kDefaultShipOptions );
}
else
{
mCreateShip( typeid( tPlanet ), "PL17", kStartPosition_Z, kNoMetaShipID,
-1, 0, 0, -1, -1, NULL, kDefaultShipOptions );
}
}
Essentially, the planet that appears is random, and will be any of the above types taken directly from the shiplist. So changes to these planets in the shiplist will effect this mission. The mission can be recompiled with different planets if you have a specific use for them and still want to use this mission in a campaign.