Each system has a level.
Eridani is level 1
Rigel (or the system after) is the first level 3
St. K's is the first level 4
levelFrequency: Describes how often you will see this kind of station. The value is always of the form: "----- ----- ------ ----- -----" where each non-space character represents a level of system (Eridani is the first level 1 system and St. K. is the first level 4 system). A dash means that station will not appear at that level, 'c' means very common, 'u' means uncommon, 'r' means rare, and 'v' means very rare.
that means if a station's frequency is:
"--rcu v---- ------ ----- -----"
it will be rare just after Rigel
it will be common just after St. K
it will be uncommon in level 5 systems
it will be very rare in level 6 systems.