Translation:The travelers are on the space station.
Is -taH used to describe a changeable state, while absence indicates an unchangeable property?
On pronouns, that's the theory, but there's no such rule presented in The Klingon Dictionary, and Okrand himself occasionally violates it. There may be something more subtle happening.
This course uses -taH or not inconsistently, and apparently without a guiding principle. Without something more concrete, it's hard to object. Still, I wish they'd decided to go with the -taH on a changeable state idea.
But note that this only applies to -taH on pronouns. On verbs, -taH just means continuous, and has nothing to do with changeability or permanence.